In 2003, Hwang et al. proposed a new blind signature based on the RSA cryptosystem by employing Extended Euclidean algorithm. They claimed that the proposed scheme was untraceable and it could meet all requirements of a blind signature. In 2004, Chang and Chang indicated that the signer in Hwang et al.' scheme could trace the blind signature applicant in some cases. However, the authors find that Chang and Chang's attack is invalid and Hwang et al.'s scheme is still untraceable in this paper.