Research of Proxy Signature with Restricted Times of Delegation

• Main Authors: Jian-Hong Wang, 王建鋐
• Other Authors: Sung-Ming Yen
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/43266249738941708431

碩士 === 國立中央大學 === 資訊工程學系 === 101 === Proxy signature, a type of digital signature, allows the original signer to authorize the proxy signer to sign documents on behalf of the original signer and this practical function becomes useful for many applications. However, unlimited delegation of signing capability might lead to security concern. If a proxy signer generates inappropriate proxy signatures with bad intention during the delegation period, the original signer may suffer great losses. To address the aforementioned issue, Choi et al. proposed a modified Schnorr signature scheme with restricted signing capability and recently Hong et al. proposed a multiple-times proxy signature scheme based on the DSA scheme. In this paper, we point out that Choi et al.'s scheme fails to satisfy strong unforgeability of the ordinary proxy signature scheme. We also demonstrate a security flaw of Hong et al.'s scheme. In addition to pointing out the flaws of these schemes, we further improve Hong et al.'s method. And we think that his method is also applicable to Schnorr signature scheme. Hence, we propose Schnorr-based proxy signature scheme with restricted times of delegation by the improved Hong et al.'s method. The above schemes are based on the discrete logarithm problem. The related research based on the factoring large integer problem has not been proposed. Hence, in this thesis, we propose an RSA-based proxy signature with restricted times of delegation. In addition to satisfying all the basic security requirements, our scheme is more efficient than Hong et al.'s scheme in the signing and verification phases.