Conditional Privacy Using Re-encryption

This paper proposes, for the first time, the use of re-encryption scheme to improve users privacy in a privacy-enhancing system. Firstly, a secure protocol to distribute a re-encryption key from a user A to a service provider B, with the help of n referees, is proposed. Next, this re-encryption key distribution protocol is combined with an existing private credential system to provide a protocol for conditional revocation of private information. This protocol has a strong accountability property with efficient online performance. It does not assume the existence of a single trusted entity. We tolerate up to t dishonest referees (t les n - 1), while A and B are dishonest and do not trust each other.