Cryptanalysis and Improvement of Identity-Based Multisignature Scheme

Abstract

Public-key encryption is an efficient mechanism providing a panoply of fundamental security services as confidentiality, authentication, integrity and non-repudiation. Effective key management and digital signatures is one of the key factors for the successful widespread deployment of public-key encryption. The digital signature is considered as one of the important mechanisms providing, in most network-based applications, one of the well-required security services, namely the authentication. In this paper, we study the security of the identity-based multisignature scheme. The scheme is based on RSA and Shamir's identity-based encryption and the message signature is shared by a coalition of known signers. We demonstrate the vulnerability of this scheme to the forgery attack, which could be carried by compromised signers, and then we propose countermeasures through a more robust scheme.