Fair Electronic Cash Based on Double Signatures

In order to decrease crimes such as money laundering, blackmailing etc.in electronic cash systems, fair electronic cash has been a major focusof academic research in electronic commence. When a bank finds somedubious cash or owner, the trusted entity or trustee can help him torevoke the anonymity of the cash. In the previous protocols, thetrustee knows all the information of the cash whether he is trusted ornot, that is, he can trace the user or cash unconditionally.Furthermore, the dishonest trustee may deceive a user, which means thathe may withdraw cash while tracing other users. Such cases are unfair tothe honest users.