A Shorter Group Signature with Verifier-Location Revocation and Backward Unlinkability

Group signatures are generalized credential/member authentication schemes with wide applications, such as Trust Computing. Membership revocation problem is a major issue of group signatures. In some applications that group secret keys are stored in tamper resistant chips, a Verifier-Local Revocation resolution is more reasonable than other methods, such as witness based revocation. Boneh et al. formally defined such VLR group signatures and proposed a VLR resolution for a short group signature. Later Nakanishi et al. pointed out it has a disadvantage of backward linkability, and provided a VLR resolution with backward unlinkability at the cost of longer signature size and more computation. We improve Nakanishi et al.’s scheme by reducing the signature size and computations required, without compromising VLR and backward unlinkability.