Improvement of a Forward-Secure Multi-Proxy Signature Scheme

This paper shows some insecurities in Xu’s forward secure multi-proxy signature scheme. There are two kinds of attacks on this scheme: (1) anyone can forge some certain messages which to be sign and cannot detect by the signature verifier. (2) This scheme can’t resist the dishonest signer forgery attack by forging its own public key. After that, the paper proposed two new forward-secure multi-proxy signature schemes based on discrete logarithm problem and quadratic residues. With verifying all the signers’ public keys, the improved schemes can resist lots of outsider attack and insider attack as above mentioned. The validity of the new scheme can be verified, and they are secure multi-signature schemes.