Repairing ElGamal-like multi-signature schemes using self-certified public keys

Abstract

Recently, Chang et al. proposed an ElGamal-like multi-signature scheme using self-certified public keys. Being inspired of the insider attack, an insider attack is proposed on their scheme to show that a malicious member in the signing group can forge a valid multi-signature without the other members’ secrete keys. To remove this attack, an improved multi-signature is also proposed.