Asymmetric Concurrent Signatures

The concept of concurrent signatures allows two entities to produce two signatures in such a way that, the signer of each signature is ambiguous from a third party’s point of view until the release of a secret, known as the keystone. Once the keystone is released, both signatures become binding to their respective signers concurrently. Previous concurrent signature schemes use the concept of ring signatures in their construction. Ring signatures identify the ring and thus concurrent signatures constructed from ring signature are related and linkable. We propose a new concurrent signature scheme which is independent of the ring signature concept. Our concurrent signatures are anonymous. The ordinary signatures obtained from our concurrent signature protocol are unlinkable and do not reveal which concurrent signature transaction has occurred. The price we pay is our concurrent signatures are asymmetric in the sense that the initial signature and subsequent signatures are not of the same construction.