Stream Ciphers: A Practical Solution for Efficient Homomorphic-Ciphertext Compression
Résumé
In typical applications of homomorphic encryption, the rst
step consists for Alice to encrypt some plaintext m under Bob's public
key pk and to send the ciphertext c = HEpk(m) to some third-party
evaluator Charlie. This paper specically considers that rst step, i.e.
the problem of transmitting c as eciently 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 c0 = (HEpk(k); Ek(m))
that Charlie decompresses homomorphically into the original c using a
decryption circuit C(E^{-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 oered 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 rmly established for over a decade, and the
new variant Kreyvium have an excellent performance.
Domaines
Cryptographie et sécurité [cs.CR]Origine | Fichiers produits par l'(les) auteur(s) |
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