Fair anonymous rewarding based on electronic cash

This manuscript presents an anonymous rewarding protocol based on electronic cash. In the protocol, a reward provider publishes a problem to solicit a satisfactory solution of the problem. The provider offers a reward to the first person that can supply her/him a satisfactory solution of the problem. A reward claimant possesses a possible solution of the problem and sends her/his solution to the provider to claim the reward. Among all the claimants, the first qualified claimant is selected to obtain the reward. Not only is the privacy of the honest claimants, including the selected claimant, protected against the provider, but also the provider cannot decline the selected claimant her/his entitled reward without being detected after acquiring the solution from the claimant. Especially, if the provider can convince the message forwarding servers in the protocol that some malicious claimant has offered a forged solution to interfere with the rewarding process, these servers will help the provider to trace the dishonest claimant.