An Electronic Contract Signing Protocol Using Fingerprint Biometrics

Fair Electronic Exchange

Fair electronic exchange can be demonstrated as e-commerce that takes place between two parties who are online and where exchange of goods and services is performed such that both parties either obtain what they expected or they obtain nothing at all. After an exchange is performed or aborted prematurely, none of the parties should have an unfair advantage over the other. If cheating takes place, where one party refuses to present their part of the exchange, other means for providing fairness should be available. These may include use of additional entities like a human judge or electronic ones that can comprehend the situation and act accordingly to provide fairness. Protocols that provide such facilities are known as fair exchange protocols. Such protocols can be used for the following purposes:

• a.

  Certified E-Mail (CEM) where a user named Alice sends a message to a user named Bob and gets a receipt from him in return. Providing the quality of fairness would include Alice getting the receipt only when Bob gets the message or Bob getting the message only when Alice gets the receipt.

• b.

  Electronic Contract Signing (ECS) where both Alice and Bob wish to sign a contract that has already been negotiated. This would involve Alice sending her commitment (digital signature) on the contract to Bob and him sending his commitment on the same in return. Providing fairness would involve Alice receiving Bob’s commitment only when her commitment is received by Bob and vice versa. This example demonstrates contract signing between two parties. However, various multi-party contract signing protocols also exist and have also been proposed in (Baum-Waidner, 2001; Ferrer-Gomila, Payeras-Capella, Huguet-Rotger, 2001; Garay & MacKenzie, 1999).

• c.

  Online payment systems (OPS) where Alice is the seller and Bob is the buyer and payment is given in return of the item of value (Cox, Tygar & Sirbu, 1995).

In the ideal case, where both Alice and Bob are guaranteed to be honest and the communication channel is secure and provides resilience, fair exchange can be achieved trivially without the aid of any external fairness provider. The above described scenarios can thus be carried out as follows:

Fair Certified E-Mail:

• Step 1: Alice sends her message to Bob.

• Step 2: Bob sends his receipt for the message to Alice. The receipt may be the digital signature of Bob on the message. Being a digital signature, this step ensures non-repudiation.