Security Analysis on a Blind Signature Scheme Based on Elgamal Signature Equation

Universal forgery attacks and selected forgery attacks on both weak and strong blind signature schemes based on Elgamal signature equation proposed by Wang et al. are developed. Without using any secret key, anyone can forge a valid signature through selecting some random parameters. The possibility of forging the blind schemes is analyzed and moreover, an improved weak blind signature scheme and an improved strong blind signature scheme are designed. Also, the securities of the improved blind signatures are analyzed.