Group signature schemes are cryptographic systems that provides revocable anonymity for the signers of messages. In this paper, we propose a group signature scheme with constant-size parameters that does not require any trapdoor secret, thereby, allows sharing of public parameters among organizations. The group manager and the revocation manager of a group can be separate parties and the size of the signature is the shortest, only one third of the size of the current state-of-the-art scheme [1]. An identity escrow scheme can be constructed as the concept dual. Under the Decisional Bilinear Diffie-Hellman and Strong Diffie-Hellman assumptions, the group signature scheme provably satisfies the conventional list of security requirements in the random oracle model and so is the identity escrow scheme in the standard model.

Abstract — Blind signatures enable users to obtain valid signatures for a message without revealing its content to the signer. This paper presents a new blind signature scheme, i.e. identity-based blind signature scheme with message recovery. Due to the message recovery property, the new scheme requires less bandwidth than the identitybased blind signatures with similar constructions. The scheme is based on modified Weil/Tate pairings over elliptic curves, and thus requires smaller key sizes for the same level of security compared to previous approaches not utilizing bilinear pairings. Security and efficiency analysis for the scheme is provided in this paper.