Paper 2009/035 Original: eprint.iacr.org/2009/035 ↗

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

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.