Stream Ciphers: A Practical Solution for Efficient Homomorphic-Ciphertext Compression

  • Anne Canteaut
  • Sergiu Carpov
  • Caroline Fontaine
  • Tancrède Lepoint
  • María Naya-Plasencia
  • Pascal Paillier
  • Renaud Sirdey
Conference paper

DOI: 10.1007/978-3-662-52993-5_16

Part of the Lecture Notes in Computer Science book series (LNCS, volume 9783)
Cite this paper as:
Canteaut A. et al. (2016) Stream Ciphers: A Practical Solution for Efficient Homomorphic-Ciphertext Compression. In: Peyrin T. (eds) Fast Software Encryption. FSE 2016. Lecture Notes in Computer Science, vol 9783. Springer, Berlin, Heidelberg

Abstract

In typical applications of homomorphic encryption, the first step consists for Alice to encrypt some plaintext m under Bob’s public key \(\mathsf {pk}\) and to send the ciphertext \(c = \mathsf {HE}_{\mathsf {pk}}(m)\) 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 \(\mathsf {E}\), Alice picks a random key k and sends a much smaller ciphertext \(c' = (\mathsf {HE}_{\mathsf {pk}}(k), \mathsf {E}_k(m))\) that Charlie decompresses homomorphically into the original c using a decryption circuit \(\mathcal {C}_{{\mathsf {E}^{-1}}}\).

In this paper, we revisit that paradigm in light of its concrete implementation constraints; in particular \(\mathsf {E}\) 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.

Keywords

Stream ciphers Homomorphic cryptography Trivium 

Copyright information

© International Association for Cryptologic Research 2016

Authors and Affiliations

  • Anne Canteaut
    • 1
  • Sergiu Carpov
    • 2
  • Caroline Fontaine
    • 3
  • Tancrède Lepoint
    • 4
  • María Naya-Plasencia
    • 1
  • Pascal Paillier
    • 4
  • Renaud Sirdey
    • 2
  1. 1.InriaParisFrance
  2. 2.CEA LISTParisFrance
  3. 3.CNRS/Lab-STICC and Telecom Bretagne and UEBBrestFrance
  4. 4.CryptoExpertsParisFrance

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