A group signature scheme allows a group member to sign messages anonymously on behalf of the group, while in case of a dispute, a designated entity can reveal the identity of a signature’s originator. Group signature schemes can be used as a basic building block for many security applications such as electronic banking systems and electronic voting. Two important issues – forward security and efficient revocation – have not been addressed by prior schemes. We construct the first forward-secure group signature schemes. While satisfying all the security properties proposed in previous group signature schemes, our schemes provide a new desired security property, forward-security: while the group public key stays fixed, a group signing key of a group member evolves over time such that compromise of a group signing key of the current time period does not enable an attacker to forge group signatures pertaining to the past time periods. Such forward-security is important to mitigate ...