Nonrepudiation is the set of controls necessary to prevent repudiation, which is the refusal by one party to acknowledge an agreement claimed by another party. For example, anticipatory repudiation, also called an anticipatory breach, is a term in the law of contracts that describes a declaration by the promising party to a contract that he or she does not intend to live up to his or her obligations under the contract. Thus, the set of controls to prevent repudiation includes both data integrity and entity authentication. However, dispute resolution between two parties invariably involves a third party such as an arbitrator or judge. Therefore, nonrepudiation requires that both data integrity and authenticity be equally provable to a third party. In Chapter 4 (Integrity), we looked at several methods.