Paper 2024/486

Anamorphic Encryption: New Constructions and Homomorphic Realizations

Dario Catalano, University of Catania
Emanuele Giunta, IMDEA Software, Universidad Politécnica de Madrid, Web3 Foundation
Francesco Migliaro, University of Catania
Abstract

The elegant paradigm of Anamorphic Encryption (Persiano et al., Eurocrypt 2022) considers the question of establishing a private communication in a world controlled by a dictator. The challenge is to allow two users, sharing some secret anamorphic key, to exchange covert messages without the dictator noticing, even when the latter has full access to the regular secret keys. Over the last year several works considered this question and proposed constructions, novel extensions and strengthened definitions. In this work we make progress on the study of this primitive in three main directions. First, we show that two general and well established encryption paradigms, namely hybrid encryption and the IBE-to-CCA transform, admit very simple and natural anamorphic extensions. Next, we show that anamorphism, far from being a phenomenon isolated to "basic" encryption schemes, extends also to homomorphic encryption. We show that some existing homomorphic schemes, (and most notably the fully homomorphic one by Gentry, Sahai and Waters) can be made anamorphic, while retaining their homomorphic properties both with respect to the regular and the covert message. Finally we refine the notion of anamorphic encryption by envisioning the possibility of splitting the anamorphic key into an encryption component (that only allows to encrypt covert messages) and a decryption component. This makes possible for a receiver to set up several, independent, covert channels associated with a single covert key.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
A major revision of an IACR publication in EUROCRYPT 2024
Keywords
Anamorphic EncryptionHomomorphic EncryptionAsymmetric Anamorphic Encryption
Contact author(s)
catalano @ dmi unict it
emanuele giunta @ imdea org
francesco migliaro @ phd unict it
History
2024-03-26: approved
2024-03-25: received
See all versions
Short URL
https://ia.cr/2024/486
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2024/486,
      author = {Dario Catalano and Emanuele Giunta and Francesco Migliaro},
      title = {Anamorphic Encryption: New Constructions and Homomorphic Realizations},
      howpublished = {Cryptology {ePrint} Archive, Paper 2024/486},
      year = {2024},
      url = {https://eprint.iacr.org/2024/486}
}
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