### Stream ciphers: A Practical Solution for Efficient Homomorphic-Ciphertext Compression

Anne Canteaut, Sergiu Carpov, Caroline Fontaine, Tancrède Lepoint, María Naya-Plasencia, Pascal Paillier, and Renaud Sirdey

##### Abstract

In typical applications of homomorphic encryption, the first step consists for Alice to encrypt some plaintext m under Bob’s public key pk and to send the ciphertext c = HE_pk(m) to some third-party evaluator Charlie. This paper specifically considers that first step, i.e. the problem of transmitting c as efficiently as possible from Alice to Charlie. As previously noted, a form of compression is achieved using hybrid encryption. Given a symmetric encryption scheme E, Alice picks a random key k and sends a much smaller ciphertext c&#8242; = (HE_pk(k), E_k(m)) that Charlie decompresses homomorphically into the original c using a decryption circuit C_E^{&#8722;1}. In this paper, we revisit that paradigm in light of its concrete implementation constraints; in particular E is chosen to be an additive IV-based stream cipher. We investigate the performances offered in this context by Trivium, which belongs to the eSTREAM portfolio, and we also propose a variant with 128-bit security: Kreyvium. We show that Trivium, whose security has been firmly established for over a decade, and the new variant Kreyvium have an excellent performance.

Available format(s)
Publication info
Preprint. MINOR revision.
Keywords
Stream CiphersHomomorphic cryptographyCiphertext compressionTrivium
Contact author(s)
tancrede lepoint @ cryptoexperts com
History
2015-11-29: last of 2 revisions
See all versions
Short URL
https://ia.cr/2015/113

CC BY

BibTeX

@misc{cryptoeprint:2015/113,
author = {Anne Canteaut and Sergiu Carpov and Caroline Fontaine and Tancrède Lepoint and María Naya-Plasencia and Pascal Paillier and Renaud Sirdey},
title = {Stream ciphers: A Practical Solution for Efficient Homomorphic-Ciphertext Compression},
howpublished = {Cryptology ePrint Archive, Paper 2015/113},
year = {2015},
note = {\url{https://eprint.iacr.org/2015/113}},
url = {https://eprint.iacr.org/2015/113}
}

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