Forward Secure Ring Signature without Random Oracles

In this paper, we propose a forward secure ring signature scheme without random oracles. With forward security, if a secret key of a corresponding ring member is exposed, all previously signed signatures containing this member remain valid. Yet the one who has stolen the secret key cannot produce any valid signature belonged to the past time period. This is especially useful in the case of ring signature, as the exposure of a single secret key may result in the invalidity of thousands or even millions ring signatures which contain that particular user. However, most of the ring signature schemes in the literature do not provide forward security. The only one with this feature [15] relies on random oracles to prove the security. We are the first to construct a forward secure ring signature scheme that can be proven secure without random oracles. Our scheme can be deployed in many applications, such as wireless sensor networks and smart grid system.