Abstract: With the development of digital signatures based on public key cryptography, key management issue decides whether digital signature technology can be widely used or not, simplifing key management becomes the new development direction of digital signature. Thus, Identity-based digital signature is proposed, which simplifies the work of key management, with the advantage of a short signature. After that, the bilinear mapping is applied to identity-based digital signature in cryptographic filed, which effectively simplifies the certificates key management and key distribution problem. Subsequently, a variety of identity-based digital signature variant schemes have been proposed, such as identity-based proxy signature, identity-based blind signature, identity-based ring signature and identity-based threshold signature and so on. The main content in this paper is identity-based proxy signature. According to the analysis of identity-based proxy signature scheme made by Wang, this paper demonstrates this solution is unsafe, although such program is proven to be secure under the random oracle model in existing references. Otherwise, the program does not meet the unforgeability, the original signer can forge a legal and valid proxy signature, proxy signer can also abuse proxy signature right. On this basis, this paper improves the original program, not only overcomes the deficiencies of the original program, but also meets the various security needs of proxy signature.

Key words: identity-based, proxy signature, bilinear mapping, security analysis