Digital signature is a foundational cryptographic primitive in modern information systems. Identity-based signatures are advantageous over signatures in the conventional public key infrastructure setting. Observing that most information systems are implemented in a multi-user setting in which some users might be corrupted, this paper proposes a new identity-based signature scheme. The new scheme is proven to be existentially unforgeable against chosen-principle and chosen-message (CP-CM) attackers who are the strongest attackers so far defined for identity-based signatures. The security of our scheme relies on the standard computational Diffie-Hellman (CDH) assumption. The proof is given in the random oracle model where a hash function modeled as random oracle. Analysis shows that our scheme is also more efficient than the state of the art in terms of computation and communication. This implies that our proposal is practical to realize efficient and secure authentication in multi-user settings.
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