Key-Insulated Group Signature Scheme with Selective Revocation

In group signature schemes, the user\´s group secret key is often stored on insecure devices e.g. mobile phones that are likely to be compromised by an adversary. Once the group secret key of a group member is found stolen, he will be revoked and can not sign documents anymore. To mitigate the damage of key exposure in group signature schemes, we proposed a key-insulated group signature scheme. The group secret key stored on an insecure device is refreshed at discrete time periods via interaction with a physically-secure device that stores a "master key ". Our scheme has secure and random-access key updates. The exposure of up to t of the N time periods, chosen adoptively by the adversary, still keeps any period that was not exposed secure. Our scheme supports selective revocation, i.e. only revoking the user\´s signing ability for some periods that were exposed, which is appropriate for the key-insulated group signature scheme.