Accountable Anonymity: A Proxy Re-Encryption Based Anonymous Communication System

While several well-developed anonymous services have been made available on-line to protect Internet user´s privacy, we have seen that due to the lack of accountability, they have often been exploited by criminals to conduct various illegal activities (e.g., sharing child pornography materials, sending threatening emails, etc.) against innocent people in both cyberspace and physical world. There is an immediate need for building accountability within anonymous systems. In this paper, we show that although accountability appears to be contradictory to and may impair anonymity, it is technically feasible to combine anonymity and accountability into one framework, namely Accountable Anonymity. To our knowledge, this is one of the first attempts trying to achieve both accountability and anonymity. We propose an efficient proxy re-encryption based design that allows normal activities to be done in anonymous manner, while keeping malicious/criminal operations accountable at the same time. Formal security analysis and prototype implementation demonstrate that our scheme is not only immune to well-known attacks against anonymity and accountability, but also able to provide non-frameability and confidentiality along with Accountable Anonymity.