Forward-secure ID based digital signature scheme with forward-secure private key generator

Abstract

In an identity based digital signature scheme, a private key generator (PKG) uses its master secret key to issue a user private key to an ID. Thus, forward secrecy of the system is not retained unless forward secrecy of the master secret key is provided. However, current forward secure identity based digital signature schemes only focus on forward secrecy of user private keys. In this paper, we capture forward secrecy of both PKG's master secret and user private keys, and formalize a new definition of "forward-secure ID based signature schemes with forward-secure PKG". Then, we design a scheme and prove its security under the BDHI assumption in the standard model (without random oracles).