Efficient Protocols for Set Membership and Range Proofs

Efficient Protocols for Set Membership and Range Proofs The goal of this master thesis was to give a major contribution in the domain of honest verifier zero-knowledge set membership and range proof. In order to do so, some investigation has been done on different cryptographic protocols for proving that a secret lies in some interval; i.e., that the (secret) discrete log of some element y to a base g lies in [a, b] for some integers a and b. There are some known techniques that address this issue. Depending on the actual size of a and b, some of these are more efficient than others. Moreover, there have been recently new more efficient proposals for specific cases that constitute the current state of the art in this field. Once the knowledge of this past work has been assimilated, we were able to propose new efficient protocols for set membership and range proof that are now in the process of being patented and published. Such protocols are an important building block for privacy protecting identity management. For instance, they allow one to ensure that an on-line forum for children is visited by 12-16 years old individuals only without that they need to reveal their full identity when requesting access.