Search

Wei Songjie et al. proposed an identity-based signature scheme（named mIBS）, and used a security mediator（SEM） node to realize real-time revocation of entity identity in the mIBS scheme. The SEM held a part of the signature key, and generated a signature by working collaboratively with a signer. This paper analyzed the security of the mIBS scheme, found it had serious security flaws, and presented a specific attack instance. In the attack instance, a signer can stole the key held by the SEM through once normal signature interaction with a SEM, and then bypassed the SEM to implement a signature independently. This paper proposed an improved signature scheme（named mIBSG）. The mIBSG scheme remedied the security flaws of the original scheme by randomizing the private key held by the SEM. Further, this paper established a security model for mIBS scheme, named mEUF-CMIA, and defined a new type of adversary that simulated malicious but legitimate signers. The new adversary had the power to generate a forged signature independently through asking random oracles. Based on the new security model, this paper deduced the unforgeability of the mIBSG scheme as solving the CDH problem on a cyclic group. Comparative analysis showed that the mIBSG scheme achieved provable security with a small calculate efficiency loss. The mIBSG scheme can be used to build an IBC-based cross-domain authentication system. [ABSTRACT FROM AUTHOR]

Fuzzy identity based signature (FIBS) possesses error-tolerance property which allows a user with identity ID described as an attribute set ω = { ω i } i = 1 n to issue a signature that could be verifed with identity I D ′ described as an attribute set ω ′ = { ω i ′ } i = 1 n if and only if ω and ω ′ are within a certain distance. Most FIBS schemes'security proofs are given in the random oracle model (ROM). Although in random oracle model the cryptographic scheme is proved to be secure, in practical applications it may be insecure. In this paper, we construct a concrete FIBS scheme and its security proof is given in the standard model(SM). Finally, we compare the proposed scheme with several other signature schemes in terms of computation, communication and security model and show that the proposed scheme is more efficient and suitable for practical applications. [ABSTRACT FROM AUTHOR]