Paper 2009/035

Key-Exposure Free Chameleon Hashing and Signatures Based on Discrete Logarithm Systems

Xiaofeng Chen, Fangguo Zhang, Haibo Tian, Baodian Wei, and Kwangjo Kim

Abstract

Chameleon signatures simultaneously provide the properties of non-repudiation and non-transferability for the signed message. However, the initial constructions of chameleon signatures suffer from the problem of key exposure. This creates a strong disincentive for the recipient to forge signatures, partially undermining the concept of non-transferability. Recently, some specific constructions of discrete logarithm based chameleon hashing and signatures without key exposure are presented, while in the setting of gap Diffile-Hellman groups with pairings. \indent \,\, In this paper, we propose the first key-exposure free chameleon hash and signature scheme based on discrete logarithm systems, without using the gap Diffile-Hellman groups. This provides more flexible constructions of efficient key-exposure free chameleon hash and signature schemes. Moreover, one distinguishing advantage of the resulting chameleon signature scheme is that the property of ``message hiding" or ``message recovery" can be achieved freely by the signer, $i.e.,$ the signer can efficiently prove which message was the original one if he desires.