An Abuse-Free Optimistic Contract Signing Protocol with Multiple TTPs

Security services become crucial to many applications such as e-commerce payment protocols, electronic contract signing, and certified e-mail delivery with the phenomenal growth of the Internet. For these applications fair exchange must be assured. A fair protocol allows two members participating in a contract to exchange digital signatures over the Internet in a fair way, so that either each person gets the other’s signature, or neither person does. As more business is conducted over the Internet, the fair-exchange problem is gaining greater importance. The property abuse-freeness is necessary for contract signing. Abuse free means,