Kristiyan Haralambiev New York University TITLE: Efficient Ring Signatures without Random Oracles ABSTRACT: We describe the first efficient ring signature scheme secure, without random oracles, based on standard assumptions. Our ring signatures are based in bilinear groups. For $l$ members of a ring our signatures consist of $2l+2$ group elements and require $2l+3$ pairings to verify. We prove our scheme secure in the strongest security model proposed by Bender, Katz, and Morselli: namely, we show our scheme to be anonymous against full key exposure and unforgeable with respect to insider corruption. A shortcoming of our approach is that all the users' keys must be defined in the same group. Authors: Hovav Shacham and Brent Waters