Analysis of an ID-based proxy signature scheme without trusted PKG and a proxy blind multi-signature scheme

This paper analyzes two proxy signature schemes' security, and proves that they exist loopholes. Xu's ID-based proxy signature scheme without trusted PKG is not safe, because there exists a security attack which original signer can tamper with the proxy warrant allayed with PKG.Hu's proxy blind multi-signature scheme also exists a security attack that the signature requester can tamper with the proxy warrant.