Non-repudiation

Non-repudiation is the assurance that an entity cannot deny a previous commitment or action by providing incontrovertible evidence. It is a security service that offers definitive proof that a particular activity has occurred. This property is essential in debatable situations whereby an entity has denied the actions performed, for example, placement of an order on an e-commerce system. This service produces cryptographic evidence in electronic transactions so that in case of disputes, it can be used as a confirmation of an action.

Non-repudiation has been an active research area for many years. Disputes in electronic transactions are a common issue, and there is a need to address them to increase the confidence level of consumers in such services.

The non-repudiation protocol usually runs in a communication network, and it is used to provide evidence that an action has been taken by an entity (originator or recipient) on the network. In this context, there are two communications models that can be used to transfer messages from originator A to recipient B:

• A message is sent directly from originator A to recipient B.
• A message is sent to a delivery agent from originator A, which then delivers the message to recipient B.

The primary requirements of a non-repudiation protocol are fairness, effectiveness, and timeliness. In many scenarios, there are multiple participants involved in a transaction, as opposed to only two parties. For example, in electronic trading systems, there can be many entities, such as clearing agents, brokers, and traders that can be involved in a single transaction. In this case, two-party non-repudiation protocols are not appropriate. To address this problem, Multi-Party Non-Repudiation (MPNR) protocols have been developed.