Security of 2^t-Root Identification and Signatures

  • Authors:
  • Claus-Peter Schnorr

  • Affiliations:
  • -

  • Venue:
  • CRYPTO '96 Proceedings of the 16th Annual International Cryptology Conference on Advances in Cryptology
  • Year:
  • 1996

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Abstract

Ong-Schnorr identification and signatures are variants of the Fiat-Shamir scheme with short and fast communication and signatures. This scheme uses secret, keys that are 2t-roots modulo N of the public keys, whereas Fiat-Shamir uses square roots modulo N. Security for particular cases has recently been proved by Micali [M94] and Shoup [ShYG]. We prove that identification and signatures are secure for arbilrary moduli N = pq unless N can easily be factored. The proven security of identification against active impersonation attacks depends on the maximal 2-power 2th that divides either p - 1 or q - 1. We show that signatures are secure against adaptive chosen-message attacks. This proves the security of a very efficient signature scheme.