Paper 2022/495

Maliciously Circuit-Private FHE from Information-Theoretic Principles

Nico Döttling and Jesko Dujmovic

Abstract

Fully homomorphic encryption (FHE) allows arbitrary computations on encrypted data. The standard security requirement, IND-CPA security, ensures that the encrypted data remain private. However, it does not guarantee privacy for the computation performed on the encrypted data. Statistical circuit privacy offers a strong privacy guarantee for the computation process, namely that a homomorphically evaluated ciphertext does not leak any information on how the result of the computation was obtained. Malicious statistical circuit privacy requires this to hold even for maliciously generated keys and ciphertexts. Ostrovsky, Paskin and Paskin (CRYPTO 2014) constructed an FHE scheme achieving malicious statistical circuit privacy. Their construction, however, makes non-black-box use of a specific underlying FHE scheme, resulting in a circuit-private scheme with inherently high overhead. This work presents a conceptually different construction of maliciously circuit-private FHE from simple information-theoretical principles. Furthermore, our construction only makes black-box use of the underlying FHE scheme, opening the possibility of achieving practically efficient schemes. Finally, in contrast to the OPP scheme in our scheme, pre- and post-homomorphic ciphertexts are syntactically the same, enabling new applications in multi-hop settings.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Published elsewhere. Major revision.ITC 2022
Keywords
Fully Homomorphic EncryptionFHEOblivious TransferMalicious Statistical Circuit PrivacyMulti-HopInformation TheoryCryptography
Contact author(s)
jesko dujmovic @ cispa de
doettling @ cispa de
History
2022-04-23: received
Short URL
https://ia.cr/2022/495
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2022/495,
      author = {Nico Döttling and Jesko Dujmovic},
      title = {Maliciously Circuit-Private FHE from Information-Theoretic Principles},
      howpublished = {Cryptology ePrint Archive, Paper 2022/495},
      year = {2022},
      note = {\url{https://eprint.iacr.org/2022/495}},
      url = {https://eprint.iacr.org/2022/495}
}
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