11692 results sorted by ID
Towards a Tightly Secure Signature in Multi-User Setting with Corruptions Based on Search Assumptions
Hirofumi Yoshioka, Wakaha Ogata, Keitaro Hashimoto
Foundations
This paper is a report on how we tackled constructing a digital signature scheme whose multi-user security with corruption can be tightly reduced to search assumptions. We fail to (dis)prove the statement but obtain the following new results:
- We reveal two new properties of signature schemes whose security cannot be tightly reduced to standard assumptions.
- We construct a new signature scheme. Its multi-user security with corruption is reduced to the CDH assumption (in the ROM), and...
$\mathsf{NTRU}\mathsf{ }\mathsf{PKE}$: Efficient Public-Key Encryption Schemes from the NTRU Problem
Jonghyun Kim, Jong Hwan Park
Public-key cryptography
We propose a new NTRU-based Public-Key Encryption (PKE) scheme called $\mathsf{NTRU }\mathsf{PKE}$, which effectively incorporates the Fujisaki-Okamoto transformation for PKE (denoted as $\mathsf{FO}_{\mathsf{PKE}}$) to achieve chosen-ciphertext security in the Quantum Random Oracle Model (QROM). While $\mathsf{NTRUEncrypt}$, a first-round candidate in the NIST PQC standardization process, was proven to be chosen-ciphertext secure in the Random Oracle Model (ROM), it lacked corresponding...
A Survey on SoC Security Verification Methods at the Pre-silicon Stage
Rasheed Kibria, Farimah Farahmandi, Mark Tehranipoor
Foundations
This paper presents a survey of the state-of-the-art pre-silicon security verification techniques for System-on-Chip (SoC) designs, focusing on ensuring that designs, implemented in hardware description languages (HDLs) and synthesized circuits, meet security requirements before fabrication in semiconductor foundries. Due to several factors, pre-silicon security verification has become an essential yet challenging aspect of the SoC hardware lifecycle. The modern SoC design process often...
Robust but Relaxed Probing Model
Nicolai Müller, Amir Moradi
Applications
Masking has become a widely applied and heavily researched method to protect cryptographic implementations against SCA attacks. The success of masking is primarily attributed to its strong theoretical foundation enabling it to formally prove security by modeling physical properties through so-called probing models. Specifically, the robust $d$-probing model enables us to prove the security for arbitrarily masked hardware circuits, manually or with the assistance of automated tools, even when...
A bound on the quantum value of all compiled nonlocal games
Alexander Kulpe, Giulio Malavolta, Connor Paddock, Simon Schmidt, Michael Walter
Foundations
A compiler introduced by Kalai et al. (STOC'23) converts any nonlocal game into an interactive protocol with a single computationally-bounded prover. Although the compiler is known to be sound in the case of classical provers, as well as complete in the quantum case, quantum soundness has so far only been established for special classes of games. In this work, we establish a quantum soundness result for all compiled two-player nonlocal games. In particular, we prove that the quantum...
AES-based CCR Hash with High Security and Its Application to Zero-Knowledge Proofs
Hongrui Cui, Chun Guo, Xiao Wang, Chenkai Weng, Kang Yang, Yu Yu
Cryptographic protocols
The recent VOLE-based interactive zero-knowledge (VOLE-ZK) protocols along with non-interactive zero-knowledge (NIZK) proofs based on MPC-in-the-Head (MPCitH) and VOLE-in-the-Head (VOLEitH) extensively utilize the commitment schemes, which adopt a circular correlation robust (CCR) hash function as the core primitive. Nevertheless, the state-of-the-art CCR hash construction by Guo et al. (S&P'20), building from random permutations, can only provide 128-bit security, when it is instantiated...
Meet-in-the-Middle Attack on 4 4 Rounds of SCARF under Single-Tweak Setting
Siwei Chen, Kai Hu, Guozhen Liu, Zhongfeng Niu, Quan Quan Tan, Shichang Wang
Attacks and cryptanalysis
\scarf, an ultra low-latency tweakable block cipher, is the first cipher designed for cache randomization.
The block cipher design is significantly different from the other common tweakable block ciphers; with a block size of only 10 bits, and yet the input key size is a whopping $240$ bits. Notably, the majority of the round key in its round function is absorbed into the data path through AND operations, rather than the typical XOR operations.
In this paper, we present a key-recovery...
Cryptographic Security through Kleene’s Theorem and Automata Theory
Mike Wa Nkongolo
Cryptographic protocols
This study addresses the challenge of strengthening cryptographic security measures in the face of evolving cyber threats. The aim is to apply Kleene's Theorem and automata theory to improve the modeling and analysis of cybersecurity scenarios, focusing on the CyberMoraba game. Representing the game's strategic moves as regular expressions and mapping them onto finite automata provides a solid framework for understanding the interactions between attackers and defenders. This approach helps...
Information-Theoretic Topology-Hiding Broadcast: Wheels, Stars, Friendship, and Beyond
D'or Banoun, Elette Boyle, Ran Cohen
Cryptographic protocols
Topology-hiding broadcast (THB) enables parties communicating over an incomplete network to broadcast messages while hiding the network topology from within a given class of graphs. Although broadcast is a privacy-free task, it is known that THB for certain graph classes necessitates computational assumptions, even against "honest but curious" adversaries, and even given a single corrupted party. Recent works have tried to understand when THB can be obtained with information-theoretic (IT)...
Safe curves for elliptic-curve cryptography
Daniel J. Bernstein, Tanja Lange
Public-key cryptography
This paper surveys interactions between choices of elliptic curves and the security of elliptic-curve cryptography. Attacks considered include not just discrete-logarithm computations but also attacks exploiting common implementation pitfalls.
A Security Analysis of Two Classes of RSA-like Cryptosystems
Paul Cotan, George Teseleanu
Public-key cryptography
Let $N=pq$ be the product of two balanced prime numbers $p$ and $q$. In 2002, Elkamchouchi, Elshenawy and Shaban introduced an RSA-like cryptosystem that uses the key equation $ed - k (p^2-1)(q^2-1) = 1$, instead of the classical RSA key equation $ed - k (p-1)(q-1) = 1$. Another variant of RSA, presented in 2017 by Murru and Saettone, uses the key equation $ed - k (p^2 p 1)(q^2 q 1) = 1$.
Despite the authors' claims of enhanced security, both schemes remain vulnerable to adaptations...
Efficient (Non-)Membership Tree from Multicollision-Resistance with Applications to Zero-Knowledge Proofs
Maksym Petkus
Cryptographic protocols
Many applications rely on accumulators and authenticated dictionaries, from timestamping certificate transparency and memory checking to blockchains and privacy-preserving decentralized electronic money, while Merkle tree and its variants are efficient for arbitrary element membership proofs, non-membership proofs, i.e., universal accumulators, and key-based membership proofs may require trees up to 256 levels for 128 bits of security, assuming binary tree, which makes it inefficient in...
Count Corruptions, Not Users: Improved Tightness for Signatures, Encryption and Authenticated Key Exchange
Mihir Bellare, Doreen Riepel, Stefano Tessaro, Yizhao Zhang
Public-key cryptography
In the multi-user with corruptions (muc) setting there are $n\geq 1$ users, and the goal is to prove that, even in the face of an adversary that adaptively corrupts users to expose their keys, un-corrupted users retain security. This can be considered for many primitives including signatures and encryption. Proofs of muc security, while possible, generally suffer a factor n loss in tightness, which can be large. This paper gives new proofs where this factor is reduced to the number c of...
Committing Wide Encryption Mode with Minimum Ciphertext Expansion
Yusuke Naito, Yu Sasaki, Takeshi Sugawara
Secret-key cryptography
We propose a new wide encryption (WE) mode of operation that satisfies robust authenticated encryption (RAE) and committing security with minimum ciphertext expansion. WE is attracting much attention in the last few years, and its advantage includes RAE security that provides robustness against wide range of misuses, combined with the encode-then-encipher (EtE) construction. Unfortunately, WE-based EtE does not provide good committing security, and there is a recent constant-time CMT-4...
Concrete Analysis of Schnorr-type Signatures with Aborts
Theo Fanuela Prabowo, Chik How Tan
Attacks and cryptanalysis
Lyubashevsky’s signature can be viewed as a lattice-based adapation of the Schnorr signature, with the core difference being the use of aborts during signature generation process. Since the proposal of Lyubashevsky’s signature, a number of other variants of Schnorr-type signatures with aborts have been proposed, both in lattice-based and code-based setting. In this paper, we examine the security of Schnorr-type signature schemes with aborts. We give a detailed analysis of when the expected...
Compass: Encrypted Semantic Search with High Accuracy
Jinhao Zhu, Liana Patel, Matei Zaharia, Raluca Ada Popa
Applications
We introduce Compass, a semantic search system over encrypted data that offers high accuracy, comparable to state-of-the-art plaintext search algorithms while protecting data, queries and search results from a fully compromised server. Compass also enables privacy-preserving RAG where both the RAG database and the query are protected. Compass's search index contributes a novel way to traverse the search graph in Hierarchical Navigable Small Worlds (HNSW), a top performing vector nearest...
Non-Interactive Zero-Knowledge from LPN and MQ
Quang Dao, Aayush Jain, Zhengzhong Jin
Cryptographic protocols
We give the first construction of non-interactive zero-knowledge (NIZK) arguments from post-quantum assumptions other than Learning with Errors. In particular, we achieve NIZK under the polynomial hardness of the Learning Parity with Noise (LPN) assumption, and the exponential hardness of solving random under-determined multivariate quadratic equations (MQ). We also construct NIZK satisfying statistical zero-knowledge assuming a new variant of LPN, Dense-Sparse LPN, introduced by Dao and...
EMI Shielding for Use in Side-Channel Security: Analysis, Simulation and Measurements
Daniel Dobkin, Edut Katz, David Popovtzer, Itamar Levi
Attacks and cryptanalysis
Considering side-channel analysis (SCA) security for cryptographic devices, the mitigation of electromagnetic leakage and electromagnetic interference (EMI) between modules poses significant challenges. This paper presents a comprehensive review and deep analysis of the utilization of EMI shielding materials, devised for reliability purposes and standards such as EMI/EMC, as a countermeasure to enhance EM-SCA security. We survey the current landscape of EMI-shields materials, including...
A Not So Discrete Sampler: Power Analysis Attacks on HAWK signature scheme
Morgane Guerreau, Mélissa Rossi
Attacks and cryptanalysis
HAWK is a lattice-based signature scheme candidate to the fourth call of the NIST's Post-Quantum standardization campaign. Considered as a cousin of Falcon (one of the future NIST post-quantum standards) one can wonder whether HAWK shares the same drawbacks as Falcon in terms of side-channel attacks. Indeed, Falcon signature algorithm and particularly its Gaussian sampler, has shown to be highly vulnerable to power-analysis attacks. Besides, efficiently protecting Falcon's signature...
Garuda and Pari: Faster and Smaller SNARKs via Equifficient Polynomial Commitments
Michel Dellepere, Pratyush Mishra, Alireza Shirzad
Cryptographic protocols
SNARKs are powerful cryptographic primitives that allow a prover to produce a succinct proof of a computation. Two key goals of SNARK research are to minimize the size of the proof and to minimize the time required to generate the proof. In this work, we present new SNARK constructions that push the frontier on both of these goals.
Our first construction, Pari, is a SNARK that achieves the smallest proof size amongst *all* known SNARKs. Specifically, Pari achieves a proof size...
Tailoring two-dimensional codes for structured lattice-based KEMs and applications to Kyber
Thales B. Paiva, Marcos A. Simplicio Jr, Syed Mahbub Hafiz, Bahattin Yildiz, Eduardo L. Cominetti
Public-key cryptography
Kyber is a post-quantum lattice-based key encapsulation mechanism (KEM) selected by NIST for standardization as ML-KEM. The scheme is designed to ensure that the unintentional errors accumulated during decryption do not prevent the receiver to correctly recover the encapsulated key. This is done by using a simple error-correction code independently applied to each bit of the message, for which it is possible to show that the decryption failure rate (DFR) is negligible. Although there have...
Beyond the Whitepaper: Where BFT Consensus Protocols Meet Reality
David Wong, Denis Kolegov, Ivan Mikushin
Implementation
This paper presents a collection of lessons learned from analyzing the real-world security of various Byzantine Fault Tolerant (BFT) consensus protocol implementations. Drawing upon our experience as a team of security experts who have both developed and audited BFT systems, including BA★, HotStuff variants, Paxos variants, and DAG-based algorithms like Narwhal and Bullshark, we identify and analyze a variety of security vulnerabilities discovered in the translation of theoretical protocols...
PROF: Protected Order Flow in a Profit-Seeking World
Kushal Babel, Nerla Jean-Louis, Yan Ji, Ujval Misra, Mahimna Kelkar, Kosala Yapa Mudiyanselage, Andrew Miller, Ari Juels
Applications
Users of decentralized finance (DeFi) applications face significant risks from adversarial actions that manipulate the order of transactions to extract value from users. Such actions---an adversarial form of what is called maximal-extractable value (MEV)---impact both individual outcomes and the stability of the DeFi ecosystem. MEV exploitation, moreover, is being institutionalized through an architectural paradigm known Proposer-Builder Separation (PBS).
This work introduces a system...
ARADI and LLAMA: Low-Latency Cryptography for Memory Encryption
Patricia Greene, Mark Motley, Bryan Weeks
Secret-key cryptography
In this paper, we describe a low-latency block cipher (ARADI) and authenticated encryption mode (LLAMA) intended to support memory encryption applications.
Dynamic Collusion Functional Encryption and Multi-Authority Attribute-Based Encryption
Rachit Garg, Rishab Goyal, George Lu
Public-key cryptography
Functional Encryption (FE) is a powerful notion of encryption which enables computations and partial message recovery of encrypted data. In FE, each decryption key is associated with a function $f$ such that decryption recovers the function evaluation $f(m)$ from an encryption of $m$. Informally, security states that a user with access to function keys $\mathsf{sk}_{f_1}, \mathsf{sk}_{f_2}, \ldots$ (and so on) can only learn $f_1(m), f_2(m), \ldots$ (and so on) but nothing more about the...
Efficient Variants of TNT with BBB Security
Ritam Bhaumik, Wonseok Choi, Avijit Dutta, Cuauhtemoc Mancillas López, Hrithik Nandi, Yaobin Shen
Secret-key cryptography
At EUROCRYPT'20, Bao et al. have shown that three-round cascading of $\textsf{LRW1}$ construction, which they dubbed as $\textsf{TNT}$, is a strong tweakable pseudorandom permutation that provably achieves $2n/3$-bit security bound. Jha et al. showed a birthday bound distinguishing attack on $\textsf{TNT}$ and invalidated the proven security bound and proved a tight birthday bound security on the $\textsf{TNT}$ construction in EUROCRYPT'24.
In a recent work, Datta et al. have...
Binding Security of Implicitly-Rejecting KEMs and Application to BIKE and HQC
Juliane Krämer, Patrick Struck, Maximiliane Weishäupl
Public-key cryptography
In this work, we continue the analysis of the binding properties of implicitly-rejecting key-encapsulation mechanisms (KEMs) obtained via the Fujisaki-Okamoto (FO) transform. These binding properties, in earlier literature known under the term robustness, thwart attacks that can arise when using KEMs in larger protocols. Recently, Cremers et al. (ePrint'24) introduced a framework for binding notions, encompassing previously existing but also new ones. While implicitly-rejecting KEMs have...
Efficient and Privacy-Preserving Collective Remote Attestation for NFV
Ghada Arfaoui, Thibaut Jacques, Cristina Onete
Cryptographic protocols
The virtualization of network functions is a promising technology, which can enable mobile network operators to provide more flexibility and better resilience for their infrastructure and services. Yet, virtualization comes with challenges, as 5G operators will require a means of verifying the state of the virtualized network components (e.g. Virtualized Network Functions (VNFs) or managing hypervisors) in order to fulfill security and privacy commitments. One such means is the use of...
A Constructive View of Homomorphic Encryption and Authenticator
Ganyuan Cao
Public-key cryptography
Homomorphic Encryption (HE) is a cutting-edge cryptographic technique that enables computations on encrypted data to be mirrored on the original data. This has quickly attracted substantial interest from the research community due to its extensive practical applications, such as in cloud computing and privacy-preserving machine learning.
In addition to confidentiality, the importance of authenticity has emerged to ensure data integrity during transmission and evaluation. To address...
Benchmarking Attacks on Learning with Errors
Emily Wenger, Eshika Saxena, Mohamed Malhou, Ellie Thieu, Kristin Lauter
Attacks and cryptanalysis
Lattice cryptography schemes based on the learning with errors (LWE) hardness assumption have been standardized by NIST for use as post-quantum cryptosystems, and by HomomorphicEncryption.org for encrypted compute on sensitive data. Thus, understanding their concrete security is critical. Most work on LWE security focuses on theoretical estimates of attack performance, which is important but may overlook attack nuances arising in real-world implementations. The sole existing concrete...
A Spectral Analysis of Noise: A Comprehensive, Automated, Formal Analysis of Diffie-Hellman Protocols
Guillaume Girol, Lucca Hirschi, Ralf Sasse, Dennis Jackson, Cas Cremers, David Basin
Cryptographic protocols
The Noise specification describes how to systematically construct a large family of Diffie-Hellman based key exchange protocols, including the secure transports used by WhatsApp, Lightning, and WireGuard. As the specification only makes informal security claims, earlier work has explored which formal security properties may be enjoyed by protocols in the Noise framework, yet many important questions remain open.
In this work we provide the most comprehensive, systematic analysis of the...
Generic Construction of Secure Sketches from Groups
Axel Durbet, Koray Karabina, Kevin Thiry-Atighehchi
Foundations
Secure sketches are designed to facilitate the recovery of originally enrolled data from inputs that may vary slightly over time. This capability is important in applications where data consistency cannot be guaranteed due to natural variations, such as in biometric systems and hardware security. Traditionally, secure sketches are constructed using error-correcting codes to handle these variations effectively. Additionally, principles of information theory ensure the security of these...
A short-list of pairing-friendly curves resistant to the Special TNFS algorithm at the 192-bit security level
Diego F. Aranha, Georgios Fotiadis, Aurore Guillevic
Implementation
For more than two decades, pairings have been a fundamental tool for designing elegant cryptosystems, varying from digital signature schemes to more complex privacy-preserving constructions. However, the advancement of quantum computing threatens to undermine public-key cryptography. Concretely, it is widely accepted that a future large-scale quantum computer would be capable to break any public-key cryptosystem used today, rendering today's public-key cryptography obsolete and mandating the...
Quantum Implementation and Analysis of ARIA
Yujin Oh, Kyungbae Jang, Yujin Yang, Hwajeong Seo
Implementation
The progression of quantum computing is considered a potential threat to traditional cryptography system, highlighting the significance of post-quantum security in cryptographic systems. Regarding symmetric key encryption, the Grover algorithm can approximately halve the search complexity. Despite the absence of fully operational quantum computers at present, the necessity of assessing the security of symmetric key encryption against quantum computing continues to grow. In this paper, we...
Depth Optimized Quantum Circuits for HIGHT and LEA
Kyungbae Jang, Yujin Oh, Minwoo Lee, Dukyoung Kim, Hwajeong Seo
Implementation
Quantum computers can model and solve several problems that have posed challenges for classical super computers, leveraging their natural quantum mechanical characteristics. A large-scale quantum computer is poised to significantly reduce security strength in cryptography. In this context, extensive research has been conducted on quantum cryptanalysis. In this paper, we present optimized quantum circuits for Korean block ciphers, HIGHT and LEA. Our quantum circuits for HIGHT and LEA...
Foldable, Recursive Proofs of Isogeny Computation with Reduced Time Complexity
Krystal Maughan, Joseph Near, Christelle Vincent
Cryptographic protocols
The security of certain post-quantum isogeny-based cryptographic schemes relies on the ability to provably and efficiently compute isogenies between supersingular elliptic curves without leaking information about the isogeny other than its domain and codomain. Earlier work in this direction give mathematical proofs of knowledge for the isogeny, and as a result when computing a chain of $n$ isogenies each proceeding node must verify the correctness of the proof of each preceding node, which...
A Compact and Parallel Swap-Based Shuffler based on butterfly Network and its complexity against Side Channel Analysis
Jong-Yeon Park, Wonil Lee, Bo Gyeong Kang, Il-jong Song, Jaekeun Oh, Kouichi Sakurai
Foundations
A prominent countermeasure against side channel attacks, the hiding countermeasure, typically involves shuffling operations using a permutation algorithm. Especially in the era of Post-Quantum Cryptography, the importance of the hiding coun- termeasure is emphasized due to computational characteristics like those of lattice and code-based cryptography. In this context, swiftly and securely generating permutations has a critical impact on an algorithm’s security and efficiency. The widely...
Falsifiability, Composability, and Comparability of Game-based Security Models for Key Exchange Protocols
Chris Brzuska, Cas Cremers, Håkon Jacobsen, Douglas Stebila, Bogdan Warinschi
Cryptographic protocols
A security proof for a key exchange protocol requires writing down a security definition. Authors typically have a clear idea of the level of security they aim to achieve. Defining the model formally additionally requires making choices on games vs. simulation-based models, partnering, on having one or more Test queries and on adopting a style of avoiding trivial attacks: exclusion, penalizing or filtering. We elucidate the consequences, advantages and disadvantages of the different possible...
Bounded-Collusion Streaming Functional Encryption from Minimal Assumptions
Kaartik Bhushan, Alexis Korb, Amit Sahai
Public-key cryptography
Streaming functional encryption (sFE), recently introduced by Guan, Korb, and Sahai [Crypto 2023], is an extension of functional encryption (FE) tailored for iterative computation on dynamic data streams. Unlike in regular FE, in an sFE scheme, users can encrypt and compute on the data as soon as it becomes available and in time proportional to just the size of the newly arrived data.
As sFE implies regular FE, all known constructions of sFE and FE for $\mathsf{P/Poly}$ require strong...
A Generic Framework for Side-Channel Attacks against LWE-based Cryptosystems
Julius Hermelink, Silvan Streit, Erik Mårtensson, Richard Petri
Attacks and cryptanalysis
Lattice-based cryptography is in the process of being standardized. Several proposals to deal with side-channel information using lattice reduction exist. However, it has been shown that algorithms based on Bayesian updating are often more favorable in practice.
In this work, we define distribution hints; a type of hint that allows modelling probabilistic information. These hints generalize most previously defined hints and the information obtained in several attacks.
We define two...
What Have SNARGs Ever Done for FHE?
Michael Walter
Public-key cryptography
In recent years, there have been several constructions combining FHE with SNARGs to add integrity guarantees to FHE schemes. Most of these works focused on improving efficiency, while the precise security model with regards to client side input privacy has remained understudied. Only recently it was shown by Manulis and Nguyen (Eurocrypt'24) that this combination does not yield IND-CCA1 security. So an interesting open question is: does the SNARG actually add any meaningful security to input...
Applying Post-Quantum Cryptography Algorithms to a DLT-Based CBDC Infrastructure: Comparative and Feasibility Analysis
Daniel de Haro Moraes, Joao Paulo Aragao Pereira, Bruno Estolano Grossi, Gustavo Mirapalheta, George Marcel Monteiro Arcuri Smetana, Wesley Rodrigues, Courtnay Nery Guimarães Jr., Bruno Domingues, Fábio Saito, Marcos Simplício
Implementation
This article presents an innovative project for a Central Bank Digital Currency (CBDC) infrastructure. Focusing on security and reliability, the proposed architecture: (1) employs post-quantum cryptography (PQC) algorithms for long-term security, even against attackers with access to cryptographically-relevant quantum computers; (2) can be integrated with a Trusted Execution Environment (TEE) to safeguard the confidentiality of transaction contents as they are processed by third-parties; and...
Preservation of Speculative Constant-time by Compilation
Santiago Arranz Olmos, Gilles Barthe, Lionel Blatter, Benjamin Grégoire, Vincent Laporte
Applications
Compilers often weaken or even discard software-based countermeasures commonly used to protect programs against side-channel attacks; worse, they may also introduce vulnerabilities that attackers can exploit. The solution to this problem is to develop compilers that preserve these countermeasures. Prior work establishes that (a mildly modified version of) the CompCert and Jasmin formally verified compilers preserve constant-time, an information flow policy that ensures that programs are...
Prover - Toward More Efficient Formal Verification of Masking in Probing Model
Feng Zhou, Hua Chen, Limin Fan
Implementation
In recent years, formal verification has emerged as a crucial method for assessing security against Side-Channel attacks of masked implementations, owing to its remarkable versatility and high degree of automation. However, formal verification still faces technical bottlenecks in balancing accuracy and efficiency, thereby limiting its scalability. Former efficient tools like \textsf{maskVerif} and CocoAlma are often inaccurate when verifying schemes utilizing properties of Boolean functions....
Optimizing Rectangle and Boomerang Attacks: A Unified and Generic Framework for Key Recovery
Qianqian Yang, Ling Song, Nana Zhang, Danping Shi, Libo Wang, Jiahao Zhao, Lei Hu, Jian Weng
Secret-key cryptography
The rectangle attack has shown to be a very powerful form of cryptanalysis against block ciphers. Given a rectangle distinguisher, one expects to mount key recovery attacks as efficiently as possible. In the literature, there have been four algorithms for rectangle key recovery attacks. However, their performance varies from case to case. Besides, numerous are the applications where the attacks lack optimality. In this paper, we delve into the rectangle key recovery and propose a unified and...
Client-Aided Privacy-Preserving Machine Learning
Peihan Miao, Xinyi Shi, Chao Wu, Ruofan Xu
Cryptographic protocols
Privacy-preserving machine learning (PPML) enables multiple distrusting parties to jointly train ML models on their private data without revealing any information beyond the final trained models. In this work, we study the client-aided two-server setting where two non-colluding servers jointly train an ML model on the data held by a large number of clients. By involving the clients in the training process, we develop efficient protocols for training algorithms including linear regression,...
Efficient Implementation of Super-optimal Pairings on Curves with Small Prime Fields at the 192-bit Security Level
Jianming Lin, Chang-An Zhao, Yuhao Zheng
Implementation
For many pairing-based cryptographic protocols such as Direct Anonymous Attestation (DAA) schemes, the arithmetic on the first pairing subgroup $\mathbb{G}_1$ is more fundamental. Such operations heavily depend on the sizes of prime fields. At the 192-bit security level, Gasnier and Guillevic presented a curve named GG22D7-457 with CM-discriminant $D = 7$ and embedding degree $k = 22$. Compared to other well-known pairing-friendly curves at the same security level, the curve GG22D7-457 has...
Hardware Implementation and Security Analysis of Local-Masked NTT for CRYSTALS-Kyber
Rafael Carrera Rodriguez, Emanuele Valea, Florent Bruguier, Pascal Benoit
Implementation
The rapid evolution of post-quantum cryptography, spurred by standardization efforts such as those led by NIST, has highlighted the prominence of lattice-based cryptography, notably exemplified by CRYSTALS-Kyber. However, concerns persist regarding the security of cryptographic implementations, particularly in the face of Side-Channel Attacks (SCA). The usage of operations like the Number Theoretic
Transform (NTT) in CRYSTALS-Kyber introduces vulnerabilities to SCA, especially single-trace...
Towards ML-KEM & ML-DSA on OpenTitan
Amin Abdulrahman, Felix Oberhansl, Hoang Nguyen Hien Pham, Jade Philipoom, Peter Schwabe, Tobias Stelzer, Andreas Zankl
Implementation
This paper presents extensions to the OpenTitan hardware root of trust that aim at enabling high-performance lattice-based cryptography. We start by carefully optimizing ML-KEM and ML-DSA - the two primary algorithms selected by NIST for standardization - in software targeting the OTBN accelerator. Based on profiling results of these implementations, we propose tightly integrated extensions to OTBN, specifically an interface from OTBN to OpenTitan's Keccak accelerator (KMAC core) and...
STORM — Small Table Oriented Redundancy-based SCA Mitigation for AES
Yaacov Belenky, Hennadii Chernyshchyk, Oleg Karavaev, Oleh Maksymenko, Valery Teper, Daria Ryzhkova, Itamar Levi, Osnat Keren, Yury Kreimer
Attacks and cryptanalysis
Side-channel-analysis (SCA) resistance with cost optimization in AES hardware implementations remains a significant challenge. While traditional masking-based schemes offer provable security, they often incur substantial resource overheads (latency, area, randomness, performance, power consumption). Alternatively, the RAMBAM scheme introduced a redundancy-based approach to control the signal-to-noise ratio, and achieves exponential leakage reduction as redundancy increases. This method...
Sanitizable and Accountable Endorsement for Dynamic Transactions in Fabric
Zhaoman Liu, Jianting Ning, Huiying Hou, Yunlei Zhao
Public-key cryptography
Hyperledger Fabric, an open-source, enterprise-grade consortium platform, employs an endorsement policy wherein a set of endorsers signs transaction proposals from clients to confirm their authenticity. The signatures from endorsers constitute the core component of endorsement. However, when dealing with dynamic transactions with high timeliness and frequent updates (e.g., stock trading, real-time ad delivery, news reporting, etc.), the current endorsement process somewhat slows down the...
Hyperion: Transparent End-to-End Verifiable Voting with Coercion Mitigation
Aditya Damodaran, Simon Rastikian, Peter B. Rønne, Peter Y A Ryan
Cryptographic protocols
We present Hyperion, an end-to-end verifiable e-voting scheme that allows the voters to identify their votes in cleartext in the final tally. In contrast to schemes like Selene or sElect, identification is not via (private) tracker numbers but via cryptographic commitment terms. After publishing the tally, the Election Authority provides each voter with an individual dual key. Voters identify their votes by raising their dual key to their secret trapdoor key and finding the matching...
AQQUA: Augmenting Quisquis with Auditability
George Papadoulis, Danai Balla, Panagiotis Grontas, Aris Pagourtzis
Applications
We propose AQQUA: a digital payment system that combines auditability and privacy. AQQUA extends Quisquis by adding two authorities; one for registration and one for auditing. These authorities do not intervene in the everyday transaction processing; as a consequence, the decentralized nature of the cryptocurrency is not disturbed. Our construction is account-based. An account consists of an updatable public key which functions as a cryptographically unlinkable pseudonym, and of commitments...
Towards Quantum-Safe Blockchain: Exploration of PQC and Public-key Recovery on Embedded Systems
Dominik Marchsreiter
Applications
Blockchain technology ensures accountability,
transparency, and redundancy in critical applications, includ-
ing IoT with embedded systems. However, the reliance on
public-key cryptography (PKC) makes blockchain vulnerable to
quantum computing threats. This paper addresses the urgent
need for quantum-safe blockchain solutions by integrating Post-
Quantum Cryptography (PQC) into blockchain frameworks.
Utilizing algorithms from the NIST PQC standardization pro-
cess, we aim to fortify...
Cryptanalysis of two post-quantum authenticated key agreement protocols
Mehdi Abri, Hamid Mala
Attacks and cryptanalysis
As the use of the internet and digital devices has grown rapidly, keeping digital communications secure has become very important. Authenticated Key Agreement (AKA) protocols play a vital role in securing digital communications. These protocols enable the communicating parties to mutually authenticate and securely establish a shared secret key. The emergence of quantum computers makes many existing AKA protocols vulnerable to their immense computational power. Consequently, designing new...
A zero-trust swarm security architecture and protocols
Alex Shafarenko
Cryptographic protocols
This report presents the security protocols and general trust architecture of the SMARTEDGE swarm computing platform. Part 1 describes the coordination protocols for use in a swarm production environment, e.g. a smart factory, and Part 2 deals with crowd-sensing scenarios characteristic of traffic-control swarms.
Cryptanalysis of Rank-2 Module-LIP with Symplectic Automorphisms
Hengyi Luo, Kaijie Jiang, Yanbin Pan, Anyu Wang
Attacks and cryptanalysis
At Eurocrypt'24, Mureau et al. formally defined the Lattice Isomorphism Problem for module lattices (module-LIP) in a number field $\mathbb{K}$, and proposed a heuristic randomized algorithm solving module-LIP for modules of rank 2 in $\mathbb{K}^2$ with a totally real number field $\mathbb{K}$, which runs in classical polynomial time for a large class of modules and a large class of totally real number field under some reasonable number theoretic assumptions. In this paper, by introducing a...
Rudraksh: A compact and lightweight post-quantum key-encapsulation mechanism
Suparna Kundu, Archisman Ghosh, Angshuman Karmakar, Shreyas Sen, Ingrid Verbauwhede
Public-key cryptography
Resource-constrained devices such as wireless sensors and Internet of Things (IoT) devices have become ubiquitous in our digital ecosystem. These devices generate and handle a major part of our digital data. In the face of the impending threat of quantum computers on our public-key infrastructure, it is impossible to imagine the security and privacy of our digital world without integrating post-quantum cryptography (PQC) into these devices. Usually, due to the resource constraints of these...
On the Relationship between FuncCPA and FuncCPA
Takumi Shinozaki, Keisuke Tanaka, Masayuki Tezuka, Yusuke Yoshida
Public-key cryptography
Akavia, Gentry, Halevi, and Vald introduced the security notion of function-chosen-plaintext-attack (FuncCPA security) for public-key encryption schemes.
FuncCPA is defined by adding a functional re-encryption oracle to the IND-CPA game.
This notion is crucial for secure computation applications where the server is allowed to delegate a part of the computation to the client.
Dodis, Halevi, and Wichs introduced a stronger variant called FuncCPA$^ $.
They showed FuncCPA$^ $ implies...
A Crack in the Firmament: Restoring Soundness of the Orion Proof System and More
Thomas den Hollander, Daniel Slamanig
Cryptographic protocols
Orion (Xie et al. CRYPTO'22) is a recent plausibly post-quantum zero-knowledge argument system with a linear time prover. It improves over Brakedown (Golovnev et al. ePrint'21 and CRYPTO'23) by reducing proof size and verifier complexity to be polylogarithmic and additionally adds the zero-knowledge property. The argument system is demonstrated to be concretely efficient with a prover time being the fastest among all existing succinct proof systems and a proof size that is an order of...
On the Number of Restricted Solutions to Constrained Systems and their Applications
Benoît Cogliati, Jordan Ethan, Ashwin Jha, Mridul Nandi, Abishanka Saha
Secret-key cryptography
In this paper, we formulate a special class of systems of linear equations over finite fields that appears naturally in the provable security analysis of several MAC and PRF modes of operation. We derive lower bounds on the number of solutions for such systems adhering to some predefined restrictions, and apply these lower bounds to derive tight PRF security for several constructions. We show security up to $2^{3n/4}$ queries for the single-keyed variant of the Double-block Hash-then-Sum...
Practical Traceable Receipt-Free Encryption
Henri Devillez, Olivier Pereira, Thomas Peters
Public-key cryptography
Traceable Receipt-free Encryption (TREnc) is a verifiable public-key encryption primitive introduced at Asiacrypt 2022. A TREnc allows randomizing ciphertexts in transit in order to remove any subliminal information up to a public trace that ensures the non-malleability of the underlying plaintext. A remarkable property of TREnc is the indistinguishability of the randomization of chosen ciphertexts against traceable chosen-ciphertext attacks (TCCA). This property can support applications...
On the Concrete Security of Non-interactive FRI
Alexander R. Block, Pratyush Ranjan Tiwari
Cryptographic protocols
FRI is a cryptographic protocol widely deployed today as a building
block of many efficient SNARKs that help secure transactions of hundreds of
millions of dollars per day. The Fiat-Shamir security of FRI—vital for understanding
the security of FRI-based SNARKs—has only recently been formalized and
established by Block et al. (ASIACRYPT ’23).
In this work, we complement the result of Block et al. by providing a thorough
concrete security analysis of non-interactive FRI under various...
Post-Quantum Access Control with Application to Secure Data Retrieval
Behzad Abdolmaleki, Hannes Blümel, Giacomo Fenzi, Homa Khajeh, Stefan Köpsell, Maryam Zarezadeh
Cryptographic protocols
Servan-Schreiber et al. (S&P 2023) presented a new notion called private access control lists (PACL) for function secret sharing (FSS), where the FSS evaluators can ensure that the FSS dealer is authorized to share the given function. Their construction relies on costly non-interactive secret-shared proofs and is not secure in post-quantum setting. We give a construction of PACL from publicly verifiable secret sharing (PVSS) under short integer solution (SIS). Our construction adapts the...
LaPSuS – A Lattice-Based Private Stream Aggregation Scheme under Scrutiny
Johannes Ottenhues, Alexander Koch
Attacks and cryptanalysis
Private Stream Aggregation (PSA) allows clients to send encryptions of their private values to an aggregator that is then able to learn the sum of these values but nothing else. It has since found many applications in practice, e.g. for smart metering or federated learning. In 2018, Becker et al. proposed the first lattice-based PSA scheme LaPS (NDSS 2018), with putative post-quantum security, which has subsequently been patented. In this paper, we describe two attacks on LaPS that break the...
Shift-invariant functions and almost liftings
Jan Kristian Haugland, Tron Omland
Foundations
We investigate shift-invariant vectorial Boolean functions on $n$ bits that are lifted from Boolean functions on $k$ bits, for $k\leq n$. We consider vectorial functions that are not necessarily permutations, but are, in some sense, almost bijective. In this context, we define an almost lifting as a Boolean function for which there is an upper bound on the number of collisions of its lifted functions that does not depend on $n$. We show that if a Boolean function with diameter $k$ is an...
Cross Ledger Transaction Consistency for Financial Auditing
Vlasis Koutsos, Xiangan Tian, Dimitrios Papadopoulos, Dimitris Chatzopoulos
Applications
Auditing throughout a fiscal year is integral to organizations with transactional activity. Organizations transact with each other and record the details for all their economical activities so that a regulatory committee can verify the lawfulness and legitimacy of their activity. However, it is computationally infeasible for the committee to perform all necessary checks for each organization. To overcome this, auditors assist in this process: organizations give access to all their internal...
Blockchain Space Tokenization
Aggelos Kiayias, Elias Koutsoupias, Philip Lazos, Giorgos Panagiotakos
Cryptographic protocols
Handling congestion in blockchain systems is a fundamental problem given that the security and decentralization objectives of such systems lead to designs that compromise on (horizontal) scalability (what sometimes is referred to as the ``blockchain trilemma''). Motivated by this, we focus on the question whether it is possible to design a transaction inclusion policy for block producers that facilitates fee and delay predictability while being incentive compatible at the same time....
Secure Multiparty Computation of Symmetric Functions with Polylogarithmic Bottleneck Complexity and Correlated Randomness
Reo Eriguchi
Cryptographic protocols
Bottleneck complexity is an efficiency measure of secure multiparty computation (MPC) protocols introduced to achieve load-balancing in large-scale networks, which is defined as the maximum communication complexity required by any one player within the protocol execution. Towards the goal of achieving low bottleneck complexity, prior works proposed MPC protocols for computing symmetric functions in the correlated randomness model, where players are given input-independent correlated...
Improved High-Order Masked Generation of Masking Vector and Rejection Sampling in Dilithium
Jean-Sébastien Coron, François Gérard, Tancrède Lepoint, Matthias Trannoy, Rina Zeitoun
Implementation
In this work, we introduce enhanced high-order masking techniques tailored for Dilithium, the post-quantum signature scheme recently standardized by NIST. We improve the masked generation of the masking vector $\vec{y}$, based on a fast Boolean-to-arithmetic conversion modulo $q$. We also describe an optimized gadget for the high-order masked rejection sampling, with a complexity independent from the size of the modulus $q$. We prove the security of our gadgets in the classical ISW...
Breaking Free: Efficient Multi-Party Private Set Union Without Non-Collusion Assumptions
Minglang Dong, Yu Chen, Cong Zhang, Yujie Bai
Cryptographic protocols
Multi-party private set union (MPSU) protocol enables $m$ $(m > 2)$ parties, each holding a set, to collectively compute the union of their sets without revealing any additional information to other parties. There are two main categories of MPSU protocols: The first builds on public-key techniques. All existing works in this category involve a super-linear number of public-key operations, resulting in poor practical efficiency. The second builds on oblivious transfer and symmetric-key...
A Practical and Scalable Implementation of the Vernam Cipher, under Shannon Conditions, using Quantum Noise
Adrian Neal
Secret-key cryptography
The one-time pad cipher is renowned for its theoretical perfect security, yet its practical deployment is primarily hindered by the key-size and distribution challenge. This paper introduces a novel approach to key distribution called q-stream, designed to make symmetric-key cryptography, and the one-time pad cipher in particular, a viable option for contemporary secure communications, and specifically, post-quantum cryptography, leveraging quantum noise and combinatorics to ensure secure...
LR-OT: Leakage-Resilient Oblivious Transfer
Francesco Berti, Carmit Hazay, Itamar Levi
Cryptographic protocols
Oblivious Transfer (OT) is a fundamental cryptographic primitive, becoming a crucial component of a practical secure protocol.
OT is typically implemented in software, and one way to accelerate its running time is by using hardware implementations.
However, such implementations are vulnerable to side-channel attacks (SCAs).
On the other hand, protecting interactive protocols against SCA is highly challenging because of their longer secrets (which include inputs and randomness), more...
Permutation Superposition Oracles for Quantum Query Lower Bounds
Christian Majenz, Giulio Malavolta, Michael Walter
Foundations
We propose a generalization of Zhandry’s compressed oracle method to random permutations, where an algorithm can query both the permutation and its inverse. We show how to use the resulting oracle simulation to bound the success probability of an algorithm for any predicate on input-output pairs, a key feature of Zhandry’s technique that had hitherto resisted attempts at generalization to random permutations. One key technical ingredient is to use strictly monotone factorizations to...
Cryptanalysis of EagleSign
Ludo N. Pulles, Mehdi Tibouchi
Attacks and cryptanalysis
EagleSign is one of the 40 “Round 1 Additional Signatures” that is accepted for consideration in the supplementary round of the Post-Quantum Cryptography standardization process, organized by NIST. Its design is based on structured lattices, and it boasts greater simplicity and performance compared to the two lattice signatures already selected for standardization: Falcon and Dilithium.
In this paper, we show that those claimed advantages come at the cost of security. More precisely, we...
Probabilistic Linearization: Internal Differential Collisions in up to 6 Rounds of SHA-3
Zhongyi Zhang, Chengan Hou, Meicheng Liu
Attacks and cryptanalysis
The SHA-3 standard consists of four cryptographic hash functions, called SHA3-224, SHA3-256, SHA3-384 and SHA3-512, and two extendable-output functions (XOFs), called SHAKE128 and SHAKE256. In this paper, we study the collision resistance of the SHA-3 instances. By analyzing the nonlinear layer, we introduce the concept of maximum difference density subspace, and develop a new target internal difference algorithm by probabilistic linearization. We also exploit new strategies for optimizing...
Exploiting signature leakages: breaking Enhanced pqsigRM
Thomas Debris-Alazard, Pierre Loisel, Valentin Vasseur
Attacks and cryptanalysis
Enhanced pqsigRM is a code-based hash-and-sign scheme proposed to the second National Institute of Standards and Technology call for post-quantum signatures. The scheme is based on the $(U,U V)$-construction and it enjoys remarkably small signature lengths, about $1$KBytes for a security level of $128$ bits. Unfortunately we show that signatures leak information about the underlying $(U,U V)$-structure. It allows to retrieve the private-key with~$100, 000$ signatures.
A New PPML Paradigm for Quantized Models
Tianpei Lu, Bingsheng Zhang, Xiaoyuan Zhang, Kui Ren
Cryptographic protocols
Model quantization has become a common practice in machine learning (ML) to improve efficiency and reduce computational/communicational overhead. However, adopting quantization in privacy-preserving machine learning (PPML) remains challenging due to the complex internal structure of quantized operators, which leads to inefficient protocols under the existing PPML frameworks.
In this work, we propose a new PPML paradigm that is tailor-made for and can benefit from quantized models. Our...
Distributed Verifiable Random Function With Compact Proof
Ahmet Ramazan Ağırtaş, Arda Buğra Özer, Zülfükar Saygı, Oğuz Yayla
Cryptographic protocols
Verifiable Random Functions (VRFs) are cryptographic primitives that generate unpredictable randomness along with proofs that are verifiable, a critical requirement for blockchain applications in decentralized finance, online gaming, and more. Existing VRF constructions often rely on centralized entities, creating security vulnerabilities. Distributed VRFs (DVRFs) offer a decentralized alternative but face challenges like large proof sizes or dependence on computationally expensive bilinear...
Cryptiny: Compacting Cryptography for Space-Restricted Channels and its Use-case for IoT-E2EE
Liron David, Omer Berkman, Avinatan Hassidim, David Lazarov, Yossi Matias, Moti Yung
We present a novel cryptographic paradigm denoted ``cryptiny:'' Employing a single cryptographic value for several security goals, thus ``compacting'' the communication sent over a space-restricted (narrow) channel, while still proving security. Cryptiny is contrary to the classical cryptographic convention of using a separate cryptographic element for each security goal.
Demonstrating the importance of cryptiny, we employ it for securing a critical IoT configuration in which a...
Curl: Private LLMs through Wavelet-Encoded Look-Up Tables
Manuel B. Santos, Dimitris Mouris, Mehmet Ugurbil, Stanislaw Jarecki, José Reis, Shubho Sengupta, Miguel de Vega
Cryptographic protocols
Recent advancements in transformers have revolutionized machine learning, forming the core of Large language models (LLMs). However, integrating these systems into everyday applications raises privacy concerns as client queries are exposed to model owners. Secure multiparty computation (MPC) allows parties to evaluate machine learning applications while keeping sensitive user inputs and proprietary models private. Due to inherent MPC costs, recent works introduce model-specific optimizations...
OPPID: Single Sign-On with Oblivious Pairwise Pseudonyms
Maximilian Kroschewski, Anja Lehmann, Cavit Özbay
Cryptographic protocols
Single Sign-On (SSO) allows users to conveniently authenticate to many Relying Parties (RPs) through a central Identity Provider (IdP). SSO supports unlinkable authentication towards the RPs via pairwise pseudonyms, where the IdP assigns the user an RP-specific pseudonym. This feature has been rolled out prominently within Apple's SSO service. While establishing unlinkable identities provides privacy towards RPs, it actually emphasizes the main privacy problem of SSO: with every...
Switching Off your Device Does Not Protect Against Fault Attacks
Paul Grandamme, Pierre-Antoine Tissot, Lilian Bossuet, Jean-Max Dutertre, Brice Colombier, Vincent Grosso
Attacks and cryptanalysis
Physical attacks, and among them fault injection attacks, are a significant threat to the security of embedded systems. Among the means of fault injection, laser has the significant advantage of being extremely spatially accurate. Numerous state-of-the-art studies have investigated the use of lasers to inject faults into a target at run-time. However, the high precision of laser fault injection comes with requirements on the knowledge of the implementation and exact execution time of the...
Finding Bugs and Features Using Cryptographically-Informed Functional Testing
Giacomo Fenzi, Jan Gilcher, Fernando Virdia
Implementation
In 2018, Mouha et al. (IEEE Trans. Reliability, 2018) performed a post-mortem investigation of the correctness of reference implementations submitted to the SHA3 competition run by NIST, finding previously unidentified bugs in a significant portion of them, including two of the five finalists. Their innovative approach allowed them to identify the presence of such bugs in a black-box manner, by searching for counterexamples to expected cryptographic properties of the implementations under...
Implementation and Performance Evaluation of Elliptic Curve Cryptography over SECP256R1 on STM32 Microprocessor
Onur İşler
Implementation
The use of Internet of Things (IoT) devices in embedded systems has become increasingly popular with advancing technologies. These devices become vulnerable to cyber attacks as they gain popularity. The cryptographic operations performed for the purpose of protection against cyber attacks are crucial to yield fast results in open networks and not slow down network traffic. Therefore, to enhance communication security, studies have been conducted in the literature on using asymmetric...
Shared-Custodial Password-Authenticated Deterministic Wallets
Poulami Das, Andreas Erwig, Sebastian Faust
Cryptographic protocols
Cryptographic wallets are an essential tool in Blockchain networks to ensure the secure storage and maintenance of an user's cryptographic keys. Broadly, wallets can be divided into three categories, namely custodial, non-custodial, and shared-custodial wallets. The first two are centralized solutions, i.e., the wallet is operated by a single entity, which inherently introduces a single point of failure. Shared-custodial wallets, on the other hand, are maintained by two independent parties,...
A Simple Post-Quantum Oblivious Transfer Protocol from Mod-LWR
Shen Dong, Hongrui Cui, Kaiyi Zhang, Kang Yang, Yu Yu
Cryptographic protocols
Oblivious transfer (OT) is a fundamental cryptographic protocol that plays a crucial role in secure multi-party computation (MPC). Most practical OT protocols by, e.g., Naor and Pinkas (SODA'01) or Chou and Orlandi (Latincrypt'15), are based on Diffie-Hellman (DH)-like assumptions and not post-quantum secure. In contrast, many other components of MPC protocols, including garbled circuits and secret sharings, are post-quantum secure. The reliance on non-post-quantum OT protocols presents a...
Ringtail: Practical Two-Round Threshold Signatures from Learning with Errors
Cecilia Boschini, Darya Kaviani, Russell W. F. Lai, Giulio Malavolta, Akira Takahashi, Mehdi Tibouchi
Cryptographic protocols
A threshold signature scheme splits the signing key among $\ell$ parties, such that any $t$-subset of parties can jointly generate signatures on a given message. Designing concretely efficient post-quantum threshold signatures is a pressing question, as evidenced by NIST's recent call.
In this work, we propose, implement, and evaluate a lattice-based threshold signature scheme, Ringtail, which is the first to achieve a combination of desirable properties:
(i) The signing...
Collision Attacks on Galois/Counter Mode (GCM)
John Preuß Mattsson
Secret-key cryptography
Advanced Encryption Standard in Galois/Counter Mode (AES-GCM) is the most widely used Authenticated Encryption with Associated Data (AEAD) algorithm in the world. In this paper, we analyze the use of GCM with all the Initialization Vector (IV) constructions and lengths approved by NIST SP 800-38D when encrypting multiple plaintexts with the same key. We derive attack complexities in both ciphertext-only and known-plaintext models, with or without nonce hiding, for collision attacks...
Legacy Encryption Downgrade Attacks against LibrePGP and CMS
Falko Strenzke, Johannes Roth
Attacks and cryptanalysis
This work describes vulnerabilities in the specification of the AEAD packets as introduced in the novel LibrePGP specification that is implemented by the widely used GnuPG application and the AES-based AEAD schemes as well as the Key Wrap
Algorithm specified in the Cryptographic Message Syntax (CMS).
These new attacks exploit the possibility to downgrade AEAD or AES Key Wrap ciphertexts to valid legacy CFB- or CBC-encrypted related ciphertexts and require that the attacker learns the...
QuickPool: Privacy-Preserving Ride-Sharing Service
Banashri Karmakar, Shyam Murthy, Arpita Patra, Protik Paul
Applications
Online ride-sharing services (RSS) have become very popular owing to increased awareness of environmental concerns and as a response to increased traffic congestion. To request a ride, users submit their locations and route information for ride matching to a service provider (SP), leading to possible privacy concerns caused by leakage of users' location data. We propose QuickPool, an efficient SP-aided RSS solution that can obliviously match multiple riders and drivers simultaneously,...
A New CRT-based Fully Homomorphic Encryption
Anil Kumar Pradhan
Cryptographic protocols
We have proposed a novel FHE scheme that uniquely encodes the plaintext with noise in a way that prevents the increasing noise from overflowing and corrupting the plaintext. This allows users to perform computations on encrypted data smoothly. The scheme is constructed using the Chinese Remainder Theorem (CRT), supporting a predefined number of modular operations on encrypted plaintext without the need for bootstrapping.
Although FHE recently became popular after Gentry's work and various...
Unforgeability of Blind Schnorr in the Limited Concurrency Setting
Franklin Harding, Jiayu Xu
Public-key cryptography
A Blind Signature Scheme (BSS) is a cryptographic primitive that enables a user to obtain a digital signature on a message from a signer without revealing the message itself. The standard security notion against malicious users for a BSS is One-More Unforgeability (OMUF). One of the earliest and most well-studied blind signature schemes is the Schnorr BSS, although recent results show it does not satisfy OMUF. On the other hand, the Schnorr BSS does satisfy the weaker notion of sequential...
Limits of Black-Box Anamorphic Encryption
Dario Catalano, Emanuele Giunta, Francesco Migliaro
Public-key cryptography
(Receiver) Anamorphic encryption, introduced by Persiano $ \textit{et al.}$ at Eurocrypt 2022, considers the question of achieving private communication in a world where secret decryption keys are under the control of a dictator. The challenge here is to be able to establish a secret communication channel to exchange covert (i.e. anamorphic) messages on top of some already deployed public key encryption scheme.
Over the last few years several works addressed this challenge by showing...
Post-Quantum Ready Key Agreement for Aviation
Marcel Tiepelt, Christian Martin, Nils Maeurer
Cryptographic protocols
Transitioning from classically to quantum secure key agreement protocols may require to exchange fundamental components, for example, exchanging Diffie-Hellman-like key exchange with a key encapsulation mechanism (KEM). Accordingly, the corresponding security proof can no longer rely on the Diffie-Hellman assumption, thus invalidating the security guarantees. As a consequence, the security properties have to be re-proven under a KEM-based security notion.
We initiate the study of the...
Fusion Channel Attack with POI Learning Encoder
Xinyao Li, Xiwen Ren, Ling Ning, Changhai Ou
Attacks and cryptanalysis
In order to challenge the security of cryptographic systems, Side-Channel Attacks exploit data leaks such as power consumption and electromagnetic emissions. Classic Side-Channel Attacks, which mainly focus on mono-channel data, fail to utilize the joint information of multi-channel data. However, previous studies of multi-channel attacks have often been limited in how they process and adapt to dynamic data. Furthermore, the different data types from various channels make it difficult to use...
Randomized Distributed Function Computation with Semantic Communications: Applications to Privacy
Onur Gunlu
Foundations
Randomized distributed function computation refers to remote function computation where transmitters send data to receivers which compute function outputs that are randomized functions of the inputs. We study the applications of semantic communications in randomized distributed function computation to illustrate significant reductions in the communication load, with a particular focus on privacy. The semantic communication framework leverages generalized remote source coding methods, where...
Quantum Implementation of LSH
Yujin Oh, Kyungbae Jang, Hwajeong Seo
Implementation
As quantum computing progresses, the assessment of cryptographic algorithm resilience against quantum attack gains significance interests in the field of cryptanalysis. Consequently, this paper implements the depth-optimized quantum circuit of Korean hash function (i.e., LSH) and estimates its quantum attack cost in quantum circuits. By utilizing an optimized quantum adder and employing parallelization techniques, the proposed quantum circuit achieves a 78.8\% improvement in full depth and a...
Practical Non-interactive Multi-signatures, and a Multi-to-Aggregate Signatures Compiler
Matthieu Rambaud, Christophe Levrat
Public-key cryptography
In a fully non-interactive multi-signature, resp. aggregate-signature scheme (fNIM, resp. fNIA), signatures issued by many signers on the same message, resp. on different messages, can be succinctly ``combined'', resp. ``aggregated''.
fNIMs are used in the Ethereum consensus protocol, to produce the certificates of validity of blocks which are to be verified by billions of clients. fNIAs are used in some PBFT-like consensus protocols, such as the production version of Diem by Aptos, to...
Separating Selective Opening Security From Standard Security, Assuming IO
Justin Holmgren, Brent Waters
Foundations
Assuming the hardness of LWE and the existence of IO, we construct a public-key encryption scheme that is IND-CCA secure but fails to satisfy even a weak notion of indistinguishability security with respect to selective opening attacks. Prior to our work, such a separation was known only from stronger assumptions such as differing inputs obfuscation (Hofheinz, Rao, and Wichs, PKC 2016).
Central to our separation is a new hash family, which may be of independent interest. Specifically,...
This paper is a report on how we tackled constructing a digital signature scheme whose multi-user security with corruption can be tightly reduced to search assumptions. We fail to (dis)prove the statement but obtain the following new results: - We reveal two new properties of signature schemes whose security cannot be tightly reduced to standard assumptions. - We construct a new signature scheme. Its multi-user security with corruption is reduced to the CDH assumption (in the ROM), and...
We propose a new NTRU-based Public-Key Encryption (PKE) scheme called $\mathsf{NTRU }\mathsf{PKE}$, which effectively incorporates the Fujisaki-Okamoto transformation for PKE (denoted as $\mathsf{FO}_{\mathsf{PKE}}$) to achieve chosen-ciphertext security in the Quantum Random Oracle Model (QROM). While $\mathsf{NTRUEncrypt}$, a first-round candidate in the NIST PQC standardization process, was proven to be chosen-ciphertext secure in the Random Oracle Model (ROM), it lacked corresponding...
This paper presents a survey of the state-of-the-art pre-silicon security verification techniques for System-on-Chip (SoC) designs, focusing on ensuring that designs, implemented in hardware description languages (HDLs) and synthesized circuits, meet security requirements before fabrication in semiconductor foundries. Due to several factors, pre-silicon security verification has become an essential yet challenging aspect of the SoC hardware lifecycle. The modern SoC design process often...
Masking has become a widely applied and heavily researched method to protect cryptographic implementations against SCA attacks. The success of masking is primarily attributed to its strong theoretical foundation enabling it to formally prove security by modeling physical properties through so-called probing models. Specifically, the robust $d$-probing model enables us to prove the security for arbitrarily masked hardware circuits, manually or with the assistance of automated tools, even when...
A compiler introduced by Kalai et al. (STOC'23) converts any nonlocal game into an interactive protocol with a single computationally-bounded prover. Although the compiler is known to be sound in the case of classical provers, as well as complete in the quantum case, quantum soundness has so far only been established for special classes of games. In this work, we establish a quantum soundness result for all compiled two-player nonlocal games. In particular, we prove that the quantum...
The recent VOLE-based interactive zero-knowledge (VOLE-ZK) protocols along with non-interactive zero-knowledge (NIZK) proofs based on MPC-in-the-Head (MPCitH) and VOLE-in-the-Head (VOLEitH) extensively utilize the commitment schemes, which adopt a circular correlation robust (CCR) hash function as the core primitive. Nevertheless, the state-of-the-art CCR hash construction by Guo et al. (S&P'20), building from random permutations, can only provide 128-bit security, when it is instantiated...
\scarf, an ultra low-latency tweakable block cipher, is the first cipher designed for cache randomization. The block cipher design is significantly different from the other common tweakable block ciphers; with a block size of only 10 bits, and yet the input key size is a whopping $240$ bits. Notably, the majority of the round key in its round function is absorbed into the data path through AND operations, rather than the typical XOR operations. In this paper, we present a key-recovery...
This study addresses the challenge of strengthening cryptographic security measures in the face of evolving cyber threats. The aim is to apply Kleene's Theorem and automata theory to improve the modeling and analysis of cybersecurity scenarios, focusing on the CyberMoraba game. Representing the game's strategic moves as regular expressions and mapping them onto finite automata provides a solid framework for understanding the interactions between attackers and defenders. This approach helps...
Topology-hiding broadcast (THB) enables parties communicating over an incomplete network to broadcast messages while hiding the network topology from within a given class of graphs. Although broadcast is a privacy-free task, it is known that THB for certain graph classes necessitates computational assumptions, even against "honest but curious" adversaries, and even given a single corrupted party. Recent works have tried to understand when THB can be obtained with information-theoretic (IT)...
This paper surveys interactions between choices of elliptic curves and the security of elliptic-curve cryptography. Attacks considered include not just discrete-logarithm computations but also attacks exploiting common implementation pitfalls.
Let $N=pq$ be the product of two balanced prime numbers $p$ and $q$. In 2002, Elkamchouchi, Elshenawy and Shaban introduced an RSA-like cryptosystem that uses the key equation $ed - k (p^2-1)(q^2-1) = 1$, instead of the classical RSA key equation $ed - k (p-1)(q-1) = 1$. Another variant of RSA, presented in 2017 by Murru and Saettone, uses the key equation $ed - k (p^2 p 1)(q^2 q 1) = 1$. Despite the authors' claims of enhanced security, both schemes remain vulnerable to adaptations...
Many applications rely on accumulators and authenticated dictionaries, from timestamping certificate transparency and memory checking to blockchains and privacy-preserving decentralized electronic money, while Merkle tree and its variants are efficient for arbitrary element membership proofs, non-membership proofs, i.e., universal accumulators, and key-based membership proofs may require trees up to 256 levels for 128 bits of security, assuming binary tree, which makes it inefficient in...
In the multi-user with corruptions (muc) setting there are $n\geq 1$ users, and the goal is to prove that, even in the face of an adversary that adaptively corrupts users to expose their keys, un-corrupted users retain security. This can be considered for many primitives including signatures and encryption. Proofs of muc security, while possible, generally suffer a factor n loss in tightness, which can be large. This paper gives new proofs where this factor is reduced to the number c of...
We propose a new wide encryption (WE) mode of operation that satisfies robust authenticated encryption (RAE) and committing security with minimum ciphertext expansion. WE is attracting much attention in the last few years, and its advantage includes RAE security that provides robustness against wide range of misuses, combined with the encode-then-encipher (EtE) construction. Unfortunately, WE-based EtE does not provide good committing security, and there is a recent constant-time CMT-4...
Lyubashevsky’s signature can be viewed as a lattice-based adapation of the Schnorr signature, with the core difference being the use of aborts during signature generation process. Since the proposal of Lyubashevsky’s signature, a number of other variants of Schnorr-type signatures with aborts have been proposed, both in lattice-based and code-based setting. In this paper, we examine the security of Schnorr-type signature schemes with aborts. We give a detailed analysis of when the expected...
We introduce Compass, a semantic search system over encrypted data that offers high accuracy, comparable to state-of-the-art plaintext search algorithms while protecting data, queries and search results from a fully compromised server. Compass also enables privacy-preserving RAG where both the RAG database and the query are protected. Compass's search index contributes a novel way to traverse the search graph in Hierarchical Navigable Small Worlds (HNSW), a top performing vector nearest...
We give the first construction of non-interactive zero-knowledge (NIZK) arguments from post-quantum assumptions other than Learning with Errors. In particular, we achieve NIZK under the polynomial hardness of the Learning Parity with Noise (LPN) assumption, and the exponential hardness of solving random under-determined multivariate quadratic equations (MQ). We also construct NIZK satisfying statistical zero-knowledge assuming a new variant of LPN, Dense-Sparse LPN, introduced by Dao and...
Considering side-channel analysis (SCA) security for cryptographic devices, the mitigation of electromagnetic leakage and electromagnetic interference (EMI) between modules poses significant challenges. This paper presents a comprehensive review and deep analysis of the utilization of EMI shielding materials, devised for reliability purposes and standards such as EMI/EMC, as a countermeasure to enhance EM-SCA security. We survey the current landscape of EMI-shields materials, including...
HAWK is a lattice-based signature scheme candidate to the fourth call of the NIST's Post-Quantum standardization campaign. Considered as a cousin of Falcon (one of the future NIST post-quantum standards) one can wonder whether HAWK shares the same drawbacks as Falcon in terms of side-channel attacks. Indeed, Falcon signature algorithm and particularly its Gaussian sampler, has shown to be highly vulnerable to power-analysis attacks. Besides, efficiently protecting Falcon's signature...
SNARKs are powerful cryptographic primitives that allow a prover to produce a succinct proof of a computation. Two key goals of SNARK research are to minimize the size of the proof and to minimize the time required to generate the proof. In this work, we present new SNARK constructions that push the frontier on both of these goals. Our first construction, Pari, is a SNARK that achieves the smallest proof size amongst *all* known SNARKs. Specifically, Pari achieves a proof size...
Kyber is a post-quantum lattice-based key encapsulation mechanism (KEM) selected by NIST for standardization as ML-KEM. The scheme is designed to ensure that the unintentional errors accumulated during decryption do not prevent the receiver to correctly recover the encapsulated key. This is done by using a simple error-correction code independently applied to each bit of the message, for which it is possible to show that the decryption failure rate (DFR) is negligible. Although there have...
This paper presents a collection of lessons learned from analyzing the real-world security of various Byzantine Fault Tolerant (BFT) consensus protocol implementations. Drawing upon our experience as a team of security experts who have both developed and audited BFT systems, including BA★, HotStuff variants, Paxos variants, and DAG-based algorithms like Narwhal and Bullshark, we identify and analyze a variety of security vulnerabilities discovered in the translation of theoretical protocols...
Users of decentralized finance (DeFi) applications face significant risks from adversarial actions that manipulate the order of transactions to extract value from users. Such actions---an adversarial form of what is called maximal-extractable value (MEV)---impact both individual outcomes and the stability of the DeFi ecosystem. MEV exploitation, moreover, is being institutionalized through an architectural paradigm known Proposer-Builder Separation (PBS). This work introduces a system...
In this paper, we describe a low-latency block cipher (ARADI) and authenticated encryption mode (LLAMA) intended to support memory encryption applications.
Functional Encryption (FE) is a powerful notion of encryption which enables computations and partial message recovery of encrypted data. In FE, each decryption key is associated with a function $f$ such that decryption recovers the function evaluation $f(m)$ from an encryption of $m$. Informally, security states that a user with access to function keys $\mathsf{sk}_{f_1}, \mathsf{sk}_{f_2}, \ldots$ (and so on) can only learn $f_1(m), f_2(m), \ldots$ (and so on) but nothing more about the...
At EUROCRYPT'20, Bao et al. have shown that three-round cascading of $\textsf{LRW1}$ construction, which they dubbed as $\textsf{TNT}$, is a strong tweakable pseudorandom permutation that provably achieves $2n/3$-bit security bound. Jha et al. showed a birthday bound distinguishing attack on $\textsf{TNT}$ and invalidated the proven security bound and proved a tight birthday bound security on the $\textsf{TNT}$ construction in EUROCRYPT'24. In a recent work, Datta et al. have...
In this work, we continue the analysis of the binding properties of implicitly-rejecting key-encapsulation mechanisms (KEMs) obtained via the Fujisaki-Okamoto (FO) transform. These binding properties, in earlier literature known under the term robustness, thwart attacks that can arise when using KEMs in larger protocols. Recently, Cremers et al. (ePrint'24) introduced a framework for binding notions, encompassing previously existing but also new ones. While implicitly-rejecting KEMs have...
The virtualization of network functions is a promising technology, which can enable mobile network operators to provide more flexibility and better resilience for their infrastructure and services. Yet, virtualization comes with challenges, as 5G operators will require a means of verifying the state of the virtualized network components (e.g. Virtualized Network Functions (VNFs) or managing hypervisors) in order to fulfill security and privacy commitments. One such means is the use of...
Homomorphic Encryption (HE) is a cutting-edge cryptographic technique that enables computations on encrypted data to be mirrored on the original data. This has quickly attracted substantial interest from the research community due to its extensive practical applications, such as in cloud computing and privacy-preserving machine learning. In addition to confidentiality, the importance of authenticity has emerged to ensure data integrity during transmission and evaluation. To address...
Lattice cryptography schemes based on the learning with errors (LWE) hardness assumption have been standardized by NIST for use as post-quantum cryptosystems, and by HomomorphicEncryption.org for encrypted compute on sensitive data. Thus, understanding their concrete security is critical. Most work on LWE security focuses on theoretical estimates of attack performance, which is important but may overlook attack nuances arising in real-world implementations. The sole existing concrete...
The Noise specification describes how to systematically construct a large family of Diffie-Hellman based key exchange protocols, including the secure transports used by WhatsApp, Lightning, and WireGuard. As the specification only makes informal security claims, earlier work has explored which formal security properties may be enjoyed by protocols in the Noise framework, yet many important questions remain open. In this work we provide the most comprehensive, systematic analysis of the...
Secure sketches are designed to facilitate the recovery of originally enrolled data from inputs that may vary slightly over time. This capability is important in applications where data consistency cannot be guaranteed due to natural variations, such as in biometric systems and hardware security. Traditionally, secure sketches are constructed using error-correcting codes to handle these variations effectively. Additionally, principles of information theory ensure the security of these...
For more than two decades, pairings have been a fundamental tool for designing elegant cryptosystems, varying from digital signature schemes to more complex privacy-preserving constructions. However, the advancement of quantum computing threatens to undermine public-key cryptography. Concretely, it is widely accepted that a future large-scale quantum computer would be capable to break any public-key cryptosystem used today, rendering today's public-key cryptography obsolete and mandating the...
The progression of quantum computing is considered a potential threat to traditional cryptography system, highlighting the significance of post-quantum security in cryptographic systems. Regarding symmetric key encryption, the Grover algorithm can approximately halve the search complexity. Despite the absence of fully operational quantum computers at present, the necessity of assessing the security of symmetric key encryption against quantum computing continues to grow. In this paper, we...
Quantum computers can model and solve several problems that have posed challenges for classical super computers, leveraging their natural quantum mechanical characteristics. A large-scale quantum computer is poised to significantly reduce security strength in cryptography. In this context, extensive research has been conducted on quantum cryptanalysis. In this paper, we present optimized quantum circuits for Korean block ciphers, HIGHT and LEA. Our quantum circuits for HIGHT and LEA...
The security of certain post-quantum isogeny-based cryptographic schemes relies on the ability to provably and efficiently compute isogenies between supersingular elliptic curves without leaking information about the isogeny other than its domain and codomain. Earlier work in this direction give mathematical proofs of knowledge for the isogeny, and as a result when computing a chain of $n$ isogenies each proceeding node must verify the correctness of the proof of each preceding node, which...
A prominent countermeasure against side channel attacks, the hiding countermeasure, typically involves shuffling operations using a permutation algorithm. Especially in the era of Post-Quantum Cryptography, the importance of the hiding coun- termeasure is emphasized due to computational characteristics like those of lattice and code-based cryptography. In this context, swiftly and securely generating permutations has a critical impact on an algorithm’s security and efficiency. The widely...
A security proof for a key exchange protocol requires writing down a security definition. Authors typically have a clear idea of the level of security they aim to achieve. Defining the model formally additionally requires making choices on games vs. simulation-based models, partnering, on having one or more Test queries and on adopting a style of avoiding trivial attacks: exclusion, penalizing or filtering. We elucidate the consequences, advantages and disadvantages of the different possible...
Streaming functional encryption (sFE), recently introduced by Guan, Korb, and Sahai [Crypto 2023], is an extension of functional encryption (FE) tailored for iterative computation on dynamic data streams. Unlike in regular FE, in an sFE scheme, users can encrypt and compute on the data as soon as it becomes available and in time proportional to just the size of the newly arrived data. As sFE implies regular FE, all known constructions of sFE and FE for $\mathsf{P/Poly}$ require strong...
Lattice-based cryptography is in the process of being standardized. Several proposals to deal with side-channel information using lattice reduction exist. However, it has been shown that algorithms based on Bayesian updating are often more favorable in practice. In this work, we define distribution hints; a type of hint that allows modelling probabilistic information. These hints generalize most previously defined hints and the information obtained in several attacks. We define two...
In recent years, there have been several constructions combining FHE with SNARGs to add integrity guarantees to FHE schemes. Most of these works focused on improving efficiency, while the precise security model with regards to client side input privacy has remained understudied. Only recently it was shown by Manulis and Nguyen (Eurocrypt'24) that this combination does not yield IND-CCA1 security. So an interesting open question is: does the SNARG actually add any meaningful security to input...
This article presents an innovative project for a Central Bank Digital Currency (CBDC) infrastructure. Focusing on security and reliability, the proposed architecture: (1) employs post-quantum cryptography (PQC) algorithms for long-term security, even against attackers with access to cryptographically-relevant quantum computers; (2) can be integrated with a Trusted Execution Environment (TEE) to safeguard the confidentiality of transaction contents as they are processed by third-parties; and...
Compilers often weaken or even discard software-based countermeasures commonly used to protect programs against side-channel attacks; worse, they may also introduce vulnerabilities that attackers can exploit. The solution to this problem is to develop compilers that preserve these countermeasures. Prior work establishes that (a mildly modified version of) the CompCert and Jasmin formally verified compilers preserve constant-time, an information flow policy that ensures that programs are...
In recent years, formal verification has emerged as a crucial method for assessing security against Side-Channel attacks of masked implementations, owing to its remarkable versatility and high degree of automation. However, formal verification still faces technical bottlenecks in balancing accuracy and efficiency, thereby limiting its scalability. Former efficient tools like \textsf{maskVerif} and CocoAlma are often inaccurate when verifying schemes utilizing properties of Boolean functions....
The rectangle attack has shown to be a very powerful form of cryptanalysis against block ciphers. Given a rectangle distinguisher, one expects to mount key recovery attacks as efficiently as possible. In the literature, there have been four algorithms for rectangle key recovery attacks. However, their performance varies from case to case. Besides, numerous are the applications where the attacks lack optimality. In this paper, we delve into the rectangle key recovery and propose a unified and...
Privacy-preserving machine learning (PPML) enables multiple distrusting parties to jointly train ML models on their private data without revealing any information beyond the final trained models. In this work, we study the client-aided two-server setting where two non-colluding servers jointly train an ML model on the data held by a large number of clients. By involving the clients in the training process, we develop efficient protocols for training algorithms including linear regression,...
For many pairing-based cryptographic protocols such as Direct Anonymous Attestation (DAA) schemes, the arithmetic on the first pairing subgroup $\mathbb{G}_1$ is more fundamental. Such operations heavily depend on the sizes of prime fields. At the 192-bit security level, Gasnier and Guillevic presented a curve named GG22D7-457 with CM-discriminant $D = 7$ and embedding degree $k = 22$. Compared to other well-known pairing-friendly curves at the same security level, the curve GG22D7-457 has...
The rapid evolution of post-quantum cryptography, spurred by standardization efforts such as those led by NIST, has highlighted the prominence of lattice-based cryptography, notably exemplified by CRYSTALS-Kyber. However, concerns persist regarding the security of cryptographic implementations, particularly in the face of Side-Channel Attacks (SCA). The usage of operations like the Number Theoretic Transform (NTT) in CRYSTALS-Kyber introduces vulnerabilities to SCA, especially single-trace...
This paper presents extensions to the OpenTitan hardware root of trust that aim at enabling high-performance lattice-based cryptography. We start by carefully optimizing ML-KEM and ML-DSA - the two primary algorithms selected by NIST for standardization - in software targeting the OTBN accelerator. Based on profiling results of these implementations, we propose tightly integrated extensions to OTBN, specifically an interface from OTBN to OpenTitan's Keccak accelerator (KMAC core) and...
Side-channel-analysis (SCA) resistance with cost optimization in AES hardware implementations remains a significant challenge. While traditional masking-based schemes offer provable security, they often incur substantial resource overheads (latency, area, randomness, performance, power consumption). Alternatively, the RAMBAM scheme introduced a redundancy-based approach to control the signal-to-noise ratio, and achieves exponential leakage reduction as redundancy increases. This method...
Hyperledger Fabric, an open-source, enterprise-grade consortium platform, employs an endorsement policy wherein a set of endorsers signs transaction proposals from clients to confirm their authenticity. The signatures from endorsers constitute the core component of endorsement. However, when dealing with dynamic transactions with high timeliness and frequent updates (e.g., stock trading, real-time ad delivery, news reporting, etc.), the current endorsement process somewhat slows down the...
We present Hyperion, an end-to-end verifiable e-voting scheme that allows the voters to identify their votes in cleartext in the final tally. In contrast to schemes like Selene or sElect, identification is not via (private) tracker numbers but via cryptographic commitment terms. After publishing the tally, the Election Authority provides each voter with an individual dual key. Voters identify their votes by raising their dual key to their secret trapdoor key and finding the matching...
We propose AQQUA: a digital payment system that combines auditability and privacy. AQQUA extends Quisquis by adding two authorities; one for registration and one for auditing. These authorities do not intervene in the everyday transaction processing; as a consequence, the decentralized nature of the cryptocurrency is not disturbed. Our construction is account-based. An account consists of an updatable public key which functions as a cryptographically unlinkable pseudonym, and of commitments...
Blockchain technology ensures accountability, transparency, and redundancy in critical applications, includ- ing IoT with embedded systems. However, the reliance on public-key cryptography (PKC) makes blockchain vulnerable to quantum computing threats. This paper addresses the urgent need for quantum-safe blockchain solutions by integrating Post- Quantum Cryptography (PQC) into blockchain frameworks. Utilizing algorithms from the NIST PQC standardization pro- cess, we aim to fortify...
As the use of the internet and digital devices has grown rapidly, keeping digital communications secure has become very important. Authenticated Key Agreement (AKA) protocols play a vital role in securing digital communications. These protocols enable the communicating parties to mutually authenticate and securely establish a shared secret key. The emergence of quantum computers makes many existing AKA protocols vulnerable to their immense computational power. Consequently, designing new...
This report presents the security protocols and general trust architecture of the SMARTEDGE swarm computing platform. Part 1 describes the coordination protocols for use in a swarm production environment, e.g. a smart factory, and Part 2 deals with crowd-sensing scenarios characteristic of traffic-control swarms.
At Eurocrypt'24, Mureau et al. formally defined the Lattice Isomorphism Problem for module lattices (module-LIP) in a number field $\mathbb{K}$, and proposed a heuristic randomized algorithm solving module-LIP for modules of rank 2 in $\mathbb{K}^2$ with a totally real number field $\mathbb{K}$, which runs in classical polynomial time for a large class of modules and a large class of totally real number field under some reasonable number theoretic assumptions. In this paper, by introducing a...
Resource-constrained devices such as wireless sensors and Internet of Things (IoT) devices have become ubiquitous in our digital ecosystem. These devices generate and handle a major part of our digital data. In the face of the impending threat of quantum computers on our public-key infrastructure, it is impossible to imagine the security and privacy of our digital world without integrating post-quantum cryptography (PQC) into these devices. Usually, due to the resource constraints of these...
Akavia, Gentry, Halevi, and Vald introduced the security notion of function-chosen-plaintext-attack (FuncCPA security) for public-key encryption schemes. FuncCPA is defined by adding a functional re-encryption oracle to the IND-CPA game. This notion is crucial for secure computation applications where the server is allowed to delegate a part of the computation to the client. Dodis, Halevi, and Wichs introduced a stronger variant called FuncCPA$^ $. They showed FuncCPA$^ $ implies...
Orion (Xie et al. CRYPTO'22) is a recent plausibly post-quantum zero-knowledge argument system with a linear time prover. It improves over Brakedown (Golovnev et al. ePrint'21 and CRYPTO'23) by reducing proof size and verifier complexity to be polylogarithmic and additionally adds the zero-knowledge property. The argument system is demonstrated to be concretely efficient with a prover time being the fastest among all existing succinct proof systems and a proof size that is an order of...
In this paper, we formulate a special class of systems of linear equations over finite fields that appears naturally in the provable security analysis of several MAC and PRF modes of operation. We derive lower bounds on the number of solutions for such systems adhering to some predefined restrictions, and apply these lower bounds to derive tight PRF security for several constructions. We show security up to $2^{3n/4}$ queries for the single-keyed variant of the Double-block Hash-then-Sum...
Traceable Receipt-free Encryption (TREnc) is a verifiable public-key encryption primitive introduced at Asiacrypt 2022. A TREnc allows randomizing ciphertexts in transit in order to remove any subliminal information up to a public trace that ensures the non-malleability of the underlying plaintext. A remarkable property of TREnc is the indistinguishability of the randomization of chosen ciphertexts against traceable chosen-ciphertext attacks (TCCA). This property can support applications...
FRI is a cryptographic protocol widely deployed today as a building block of many efficient SNARKs that help secure transactions of hundreds of millions of dollars per day. The Fiat-Shamir security of FRI—vital for understanding the security of FRI-based SNARKs—has only recently been formalized and established by Block et al. (ASIACRYPT ’23). In this work, we complement the result of Block et al. by providing a thorough concrete security analysis of non-interactive FRI under various...
Servan-Schreiber et al. (S&P 2023) presented a new notion called private access control lists (PACL) for function secret sharing (FSS), where the FSS evaluators can ensure that the FSS dealer is authorized to share the given function. Their construction relies on costly non-interactive secret-shared proofs and is not secure in post-quantum setting. We give a construction of PACL from publicly verifiable secret sharing (PVSS) under short integer solution (SIS). Our construction adapts the...
Private Stream Aggregation (PSA) allows clients to send encryptions of their private values to an aggregator that is then able to learn the sum of these values but nothing else. It has since found many applications in practice, e.g. for smart metering or federated learning. In 2018, Becker et al. proposed the first lattice-based PSA scheme LaPS (NDSS 2018), with putative post-quantum security, which has subsequently been patented. In this paper, we describe two attacks on LaPS that break the...
We investigate shift-invariant vectorial Boolean functions on $n$ bits that are lifted from Boolean functions on $k$ bits, for $k\leq n$. We consider vectorial functions that are not necessarily permutations, but are, in some sense, almost bijective. In this context, we define an almost lifting as a Boolean function for which there is an upper bound on the number of collisions of its lifted functions that does not depend on $n$. We show that if a Boolean function with diameter $k$ is an...
Auditing throughout a fiscal year is integral to organizations with transactional activity. Organizations transact with each other and record the details for all their economical activities so that a regulatory committee can verify the lawfulness and legitimacy of their activity. However, it is computationally infeasible for the committee to perform all necessary checks for each organization. To overcome this, auditors assist in this process: organizations give access to all their internal...
Handling congestion in blockchain systems is a fundamental problem given that the security and decentralization objectives of such systems lead to designs that compromise on (horizontal) scalability (what sometimes is referred to as the ``blockchain trilemma''). Motivated by this, we focus on the question whether it is possible to design a transaction inclusion policy for block producers that facilitates fee and delay predictability while being incentive compatible at the same time....
Bottleneck complexity is an efficiency measure of secure multiparty computation (MPC) protocols introduced to achieve load-balancing in large-scale networks, which is defined as the maximum communication complexity required by any one player within the protocol execution. Towards the goal of achieving low bottleneck complexity, prior works proposed MPC protocols for computing symmetric functions in the correlated randomness model, where players are given input-independent correlated...
In this work, we introduce enhanced high-order masking techniques tailored for Dilithium, the post-quantum signature scheme recently standardized by NIST. We improve the masked generation of the masking vector $\vec{y}$, based on a fast Boolean-to-arithmetic conversion modulo $q$. We also describe an optimized gadget for the high-order masked rejection sampling, with a complexity independent from the size of the modulus $q$. We prove the security of our gadgets in the classical ISW...
Multi-party private set union (MPSU) protocol enables $m$ $(m > 2)$ parties, each holding a set, to collectively compute the union of their sets without revealing any additional information to other parties. There are two main categories of MPSU protocols: The first builds on public-key techniques. All existing works in this category involve a super-linear number of public-key operations, resulting in poor practical efficiency. The second builds on oblivious transfer and symmetric-key...
The one-time pad cipher is renowned for its theoretical perfect security, yet its practical deployment is primarily hindered by the key-size and distribution challenge. This paper introduces a novel approach to key distribution called q-stream, designed to make symmetric-key cryptography, and the one-time pad cipher in particular, a viable option for contemporary secure communications, and specifically, post-quantum cryptography, leveraging quantum noise and combinatorics to ensure secure...
Oblivious Transfer (OT) is a fundamental cryptographic primitive, becoming a crucial component of a practical secure protocol. OT is typically implemented in software, and one way to accelerate its running time is by using hardware implementations. However, such implementations are vulnerable to side-channel attacks (SCAs). On the other hand, protecting interactive protocols against SCA is highly challenging because of their longer secrets (which include inputs and randomness), more...
We propose a generalization of Zhandry’s compressed oracle method to random permutations, where an algorithm can query both the permutation and its inverse. We show how to use the resulting oracle simulation to bound the success probability of an algorithm for any predicate on input-output pairs, a key feature of Zhandry’s technique that had hitherto resisted attempts at generalization to random permutations. One key technical ingredient is to use strictly monotone factorizations to...
EagleSign is one of the 40 “Round 1 Additional Signatures” that is accepted for consideration in the supplementary round of the Post-Quantum Cryptography standardization process, organized by NIST. Its design is based on structured lattices, and it boasts greater simplicity and performance compared to the two lattice signatures already selected for standardization: Falcon and Dilithium. In this paper, we show that those claimed advantages come at the cost of security. More precisely, we...
The SHA-3 standard consists of four cryptographic hash functions, called SHA3-224, SHA3-256, SHA3-384 and SHA3-512, and two extendable-output functions (XOFs), called SHAKE128 and SHAKE256. In this paper, we study the collision resistance of the SHA-3 instances. By analyzing the nonlinear layer, we introduce the concept of maximum difference density subspace, and develop a new target internal difference algorithm by probabilistic linearization. We also exploit new strategies for optimizing...
Enhanced pqsigRM is a code-based hash-and-sign scheme proposed to the second National Institute of Standards and Technology call for post-quantum signatures. The scheme is based on the $(U,U V)$-construction and it enjoys remarkably small signature lengths, about $1$KBytes for a security level of $128$ bits. Unfortunately we show that signatures leak information about the underlying $(U,U V)$-structure. It allows to retrieve the private-key with~$100, 000$ signatures.
Model quantization has become a common practice in machine learning (ML) to improve efficiency and reduce computational/communicational overhead. However, adopting quantization in privacy-preserving machine learning (PPML) remains challenging due to the complex internal structure of quantized operators, which leads to inefficient protocols under the existing PPML frameworks. In this work, we propose a new PPML paradigm that is tailor-made for and can benefit from quantized models. Our...
Verifiable Random Functions (VRFs) are cryptographic primitives that generate unpredictable randomness along with proofs that are verifiable, a critical requirement for blockchain applications in decentralized finance, online gaming, and more. Existing VRF constructions often rely on centralized entities, creating security vulnerabilities. Distributed VRFs (DVRFs) offer a decentralized alternative but face challenges like large proof sizes or dependence on computationally expensive bilinear...
We present a novel cryptographic paradigm denoted ``cryptiny:'' Employing a single cryptographic value for several security goals, thus ``compacting'' the communication sent over a space-restricted (narrow) channel, while still proving security. Cryptiny is contrary to the classical cryptographic convention of using a separate cryptographic element for each security goal. Demonstrating the importance of cryptiny, we employ it for securing a critical IoT configuration in which a...
Recent advancements in transformers have revolutionized machine learning, forming the core of Large language models (LLMs). However, integrating these systems into everyday applications raises privacy concerns as client queries are exposed to model owners. Secure multiparty computation (MPC) allows parties to evaluate machine learning applications while keeping sensitive user inputs and proprietary models private. Due to inherent MPC costs, recent works introduce model-specific optimizations...
Single Sign-On (SSO) allows users to conveniently authenticate to many Relying Parties (RPs) through a central Identity Provider (IdP). SSO supports unlinkable authentication towards the RPs via pairwise pseudonyms, where the IdP assigns the user an RP-specific pseudonym. This feature has been rolled out prominently within Apple's SSO service. While establishing unlinkable identities provides privacy towards RPs, it actually emphasizes the main privacy problem of SSO: with every...
Physical attacks, and among them fault injection attacks, are a significant threat to the security of embedded systems. Among the means of fault injection, laser has the significant advantage of being extremely spatially accurate. Numerous state-of-the-art studies have investigated the use of lasers to inject faults into a target at run-time. However, the high precision of laser fault injection comes with requirements on the knowledge of the implementation and exact execution time of the...
In 2018, Mouha et al. (IEEE Trans. Reliability, 2018) performed a post-mortem investigation of the correctness of reference implementations submitted to the SHA3 competition run by NIST, finding previously unidentified bugs in a significant portion of them, including two of the five finalists. Their innovative approach allowed them to identify the presence of such bugs in a black-box manner, by searching for counterexamples to expected cryptographic properties of the implementations under...
The use of Internet of Things (IoT) devices in embedded systems has become increasingly popular with advancing technologies. These devices become vulnerable to cyber attacks as they gain popularity. The cryptographic operations performed for the purpose of protection against cyber attacks are crucial to yield fast results in open networks and not slow down network traffic. Therefore, to enhance communication security, studies have been conducted in the literature on using asymmetric...
Cryptographic wallets are an essential tool in Blockchain networks to ensure the secure storage and maintenance of an user's cryptographic keys. Broadly, wallets can be divided into three categories, namely custodial, non-custodial, and shared-custodial wallets. The first two are centralized solutions, i.e., the wallet is operated by a single entity, which inherently introduces a single point of failure. Shared-custodial wallets, on the other hand, are maintained by two independent parties,...
Oblivious transfer (OT) is a fundamental cryptographic protocol that plays a crucial role in secure multi-party computation (MPC). Most practical OT protocols by, e.g., Naor and Pinkas (SODA'01) or Chou and Orlandi (Latincrypt'15), are based on Diffie-Hellman (DH)-like assumptions and not post-quantum secure. In contrast, many other components of MPC protocols, including garbled circuits and secret sharings, are post-quantum secure. The reliance on non-post-quantum OT protocols presents a...
A threshold signature scheme splits the signing key among $\ell$ parties, such that any $t$-subset of parties can jointly generate signatures on a given message. Designing concretely efficient post-quantum threshold signatures is a pressing question, as evidenced by NIST's recent call. In this work, we propose, implement, and evaluate a lattice-based threshold signature scheme, Ringtail, which is the first to achieve a combination of desirable properties: (i) The signing...
Advanced Encryption Standard in Galois/Counter Mode (AES-GCM) is the most widely used Authenticated Encryption with Associated Data (AEAD) algorithm in the world. In this paper, we analyze the use of GCM with all the Initialization Vector (IV) constructions and lengths approved by NIST SP 800-38D when encrypting multiple plaintexts with the same key. We derive attack complexities in both ciphertext-only and known-plaintext models, with or without nonce hiding, for collision attacks...
This work describes vulnerabilities in the specification of the AEAD packets as introduced in the novel LibrePGP specification that is implemented by the widely used GnuPG application and the AES-based AEAD schemes as well as the Key Wrap Algorithm specified in the Cryptographic Message Syntax (CMS). These new attacks exploit the possibility to downgrade AEAD or AES Key Wrap ciphertexts to valid legacy CFB- or CBC-encrypted related ciphertexts and require that the attacker learns the...
Online ride-sharing services (RSS) have become very popular owing to increased awareness of environmental concerns and as a response to increased traffic congestion. To request a ride, users submit their locations and route information for ride matching to a service provider (SP), leading to possible privacy concerns caused by leakage of users' location data. We propose QuickPool, an efficient SP-aided RSS solution that can obliviously match multiple riders and drivers simultaneously,...
We have proposed a novel FHE scheme that uniquely encodes the plaintext with noise in a way that prevents the increasing noise from overflowing and corrupting the plaintext. This allows users to perform computations on encrypted data smoothly. The scheme is constructed using the Chinese Remainder Theorem (CRT), supporting a predefined number of modular operations on encrypted plaintext without the need for bootstrapping. Although FHE recently became popular after Gentry's work and various...
A Blind Signature Scheme (BSS) is a cryptographic primitive that enables a user to obtain a digital signature on a message from a signer without revealing the message itself. The standard security notion against malicious users for a BSS is One-More Unforgeability (OMUF). One of the earliest and most well-studied blind signature schemes is the Schnorr BSS, although recent results show it does not satisfy OMUF. On the other hand, the Schnorr BSS does satisfy the weaker notion of sequential...
(Receiver) Anamorphic encryption, introduced by Persiano $ \textit{et al.}$ at Eurocrypt 2022, considers the question of achieving private communication in a world where secret decryption keys are under the control of a dictator. The challenge here is to be able to establish a secret communication channel to exchange covert (i.e. anamorphic) messages on top of some already deployed public key encryption scheme. Over the last few years several works addressed this challenge by showing...
Transitioning from classically to quantum secure key agreement protocols may require to exchange fundamental components, for example, exchanging Diffie-Hellman-like key exchange with a key encapsulation mechanism (KEM). Accordingly, the corresponding security proof can no longer rely on the Diffie-Hellman assumption, thus invalidating the security guarantees. As a consequence, the security properties have to be re-proven under a KEM-based security notion. We initiate the study of the...
In order to challenge the security of cryptographic systems, Side-Channel Attacks exploit data leaks such as power consumption and electromagnetic emissions. Classic Side-Channel Attacks, which mainly focus on mono-channel data, fail to utilize the joint information of multi-channel data. However, previous studies of multi-channel attacks have often been limited in how they process and adapt to dynamic data. Furthermore, the different data types from various channels make it difficult to use...
Randomized distributed function computation refers to remote function computation where transmitters send data to receivers which compute function outputs that are randomized functions of the inputs. We study the applications of semantic communications in randomized distributed function computation to illustrate significant reductions in the communication load, with a particular focus on privacy. The semantic communication framework leverages generalized remote source coding methods, where...
As quantum computing progresses, the assessment of cryptographic algorithm resilience against quantum attack gains significance interests in the field of cryptanalysis. Consequently, this paper implements the depth-optimized quantum circuit of Korean hash function (i.e., LSH) and estimates its quantum attack cost in quantum circuits. By utilizing an optimized quantum adder and employing parallelization techniques, the proposed quantum circuit achieves a 78.8\% improvement in full depth and a...
In a fully non-interactive multi-signature, resp. aggregate-signature scheme (fNIM, resp. fNIA), signatures issued by many signers on the same message, resp. on different messages, can be succinctly ``combined'', resp. ``aggregated''. fNIMs are used in the Ethereum consensus protocol, to produce the certificates of validity of blocks which are to be verified by billions of clients. fNIAs are used in some PBFT-like consensus protocols, such as the production version of Diem by Aptos, to...
Assuming the hardness of LWE and the existence of IO, we construct a public-key encryption scheme that is IND-CCA secure but fails to satisfy even a weak notion of indistinguishability security with respect to selective opening attacks. Prior to our work, such a separation was known only from stronger assumptions such as differing inputs obfuscation (Hofheinz, Rao, and Wichs, PKC 2016). Central to our separation is a new hash family, which may be of independent interest. Specifically,...