Paper 2023/1699

Oblivious Homomorphic Encryption

Osman Biçer, University of Basel
Christian Tschudin, University of Basel
Abstract

In this paper, we introduce Oblivious Homomorphic Encryption (OHE) which provably separates the computation spaces of multiple clients of a fully homomorphic encryption (FHE) service while keeping the evaluator blind about whom a result belongs. We justify the importance of this strict isolation property of OHE by showing an attack on a recently proposed key-private cryptocurrency scheme. Our two OHE constructions are based on a puncturing function where the evaluator can effectively mask ciphertexts from rogue and potentially colluding clients. In the first construction OHE1, we show that this can be im- plemented via an FHE scheme (with key privacy and weak wrong-key decryption properties) plus an anonymous commitment scheme. The second construction OHE2, for flexibility of primitive choice, achieves this via a combination of a standard FHE scheme, an encryption scheme with key privacy and weak wrong-key decryption, and an anonymous commitment scheme. OHE can be used to provide provable anonymity to cloud applications, single server implementations of anonymous messaging as well as account-based cryptocurrencies.

Metadata
Available format(s)
PDF
Category
Cryptographic protocols
Publication info
Preprint.
Keywords
fully homomorphic encryptionkey privacycloud data privacyoblivious message retrievalanonymous cryptocurrencies
Contact author(s)
osman bicer @ unibas ch
christian tschudin @ unibas ch
History
2023-11-14: last of 25 revisions
2023-11-02: received
See all versions
Short URL
https://ia.cr/2023/1699
License
Creative Commons Attribution-NonCommercial-ShareAlike
CC BY-NC-SA

BibTeX

@misc{cryptoeprint:2023/1699,
      author = {Osman Biçer and Christian Tschudin},
      title = {Oblivious Homomorphic Encryption},
      howpublished = {Cryptology {ePrint} Archive, Paper 2023/1699},
      year = {2023},
      url = {https://eprint.iacr.org/2023/1699}
}
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