Forking Lemmas in the Ring Signatures' Scenario.
Javier Herranz, Germán Sáez · 2003
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 modication 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 ring) of potential signers pro-duces 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. 1