Fully homomorphic encryption over the integers with shorter public keys

  • Authors:
  • Jean-Sébastien Coron;Avradip Mandal;David Naccache;Mehdi Tibouchi

  • Affiliations:
  • Université du Luxembourg;Université du Luxembourg;Ecole normale supérieure;Université du Luxembourg and Ecole normale supérieure

  • Venue:
  • CRYPTO'11 Proceedings of the 31st annual conference on Advances in cryptology
  • Year:
  • 2011

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Abstract

At Eurocrypt 2010 van Dijk et al. described a fully homomorphic encryption scheme over the integers. The main appeal of this scheme (compared to Gentry's) is its conceptual simplicity. This simplicity comes at the expense of a public key size in Õ(λ10) which is too large for any practical system. In this paper we reduce the public key size to Õ(λ7) by encrypting with a quadratic form in the public key elements, instead of a linear form. We prove that the scheme remains semantically secure, based on a stronger variant of the approximate-GCD problem, already considered by van Dijk et al. We alsodescribe the first implementation of the resulting fully homomorphic scheme. Borrowing some optimizations from the recent Gentry-Halevi implementation of Gentry's scheme, we obtain roughly the same level of efficiency. This shows that fully homomorphic encryption can be implemented using simple arithmetic operations.