International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Forking Lemmas in the Ring Signatures' Scenario

Javier Herranz
Germ\'an S\'aez
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Abstract: Pointcheval and Stern introduced in 1996 some forking lemmas useful to prove the security of a family of digital signature schemes. This family includes, for example, Schnorr's scheme and a modification of ElGamal signature scheme. In this work we generalize these forking lemmas to the ring signatures' scenario. In a ring signature scheme, a signer in a subset (or {\it ring}) of potential signers produces a signature of a message in such a way that the receiver can verify that the signature comes from a member of the ring, but cannot know which member has actually signed. We propose a new ring signature scheme, based on Schnorr signature scheme, which provides unconditional anonymity. We use the generalized forking lemmas to prove that this scheme is existentially unforgeable under adaptive chosen-message attacks, in the random oracle model.
  title={Forking Lemmas in the Ring Signatures' Scenario},
  booktitle={IACR Eprint archive},
  keywords={public-key cryptography / ring signature schemes, unforgeability against chosen-message attacks, random oracle model},
  note={ 12152 received 10 Apr 2003},
  author={Javier Herranz and Germ\'an S\'aez},