Achieving liability in anonymous communication: Auditing and tracing

The emergence of anonymity abusing in anonymous communication has received considerable attention. Achieving the liability of auditing and tracing illegal users becomes to be a critical requirement. Although some anonymity abusing control strategies have been proposed, they mostly possess no prior audit judgment function. In this paper, we propose a linkable group signature mechanism to simultaneously achieve the functions of anonymity, auditing and tracing for communication sender. Specifically, we propose a general construction of linkable group signature using the basic cryptography modules of blind signature, public key encryption, trapdoor indicative commitment and signature of knowledge, and further extend it to a multi-authority environment based on distributed key generation protocol. Following the frameworks, we present concrete linkable group signature instances. Security and performance analyses confirm that our schemes are practical. Furthermore, we first formally define a new concept called trapdoor indicative commitment, which is applicable to judge whether given committed values are equal without opening the commitments.