The design of ID-based fair proxy blind signature scheme with weak linkability

The blind signature scheme is a very useful protocol for a requester to obtain a signature on a message from a signer without revealing the linkage of the message content and the signature to the signer. After Chaum's scheme was first proposed in 1982, many extended protocols have been published and already used for many related applications. In 1995, the fair blind signature was first introduced by Stadler et al., in which a property of fairness was added to the ordinary blind signature scheme. The protocol provided an additional trusted third party (TTP) to prevent the abused problems. A variant scheme named the proxy blind signature scheme has been proposed which combined the advantages of the blind signature and the proxy signature. A blind signature can provide the perfect unlinkability for people to protect their privacy. However, it may be more useful for the commercial applications if the blind signature can provide a weak linkability between different message-signature pairs. Certainly, the weakly linkable blind signature must ensure that it can protect personal privacy of the requester. In this paper, we propose an ID-based fair proxy blind signature scheme with weak linkability to help the requester linking some signatures they used, but not leak his personal privacy of identity. Especially, it is the first work to combine the blind signature with the weak linkability, fairness and proxy signing techniques.