Date Added: May 2012
A prominent issue in group signatures is revoking a group member's signing capability. To solve this issue, the group manager can send revocation messages only to signature verifiers, known as group signatures with Verifier-Local Revocation (VLR). In existing VLR designs, the cost of revocation check grows linearly with the size of revocation messages. This paper introduces time-bound keys into group signatures to reduce the size of revocation messages and speed up the revocation check. In the new notion, the secret key of each group member is associated with an expiration date, and verifiers can tell (at a constant cost) whether or not a group signature is produced using an expired key.