Two Simple Attacks on a Blind Signature Scheme

A blind signature scheme allows a user to obtain a signature on a given message without revealing any information about the message to the signer. The idea of blind signature was first introduced by Chaum at CRYPTO 1982. Blind signatures can be used in many applications, such as e-voting. Recently, Chakraborty and Mehta proposed a new blind signature scheme (Chakraborty-Mehta scheme) based on the elliptic curve discrete logarithm problem. They asserted that their blind signature scheme is secure. In this paper, however, we will present two simple but powerful attacks on their blind signature scheme. The attacks show Chakraborty-Mehta blind signature scheme is not secure.