Nonrepudiation is a term used in information security that means the inability to deny the validity or authenticity of a contract, agreement, or obligation. There are various synonyms for this word such as authentication, validation, verification, substantiation, and confirmation. These terms are used to define the processes or techniques that prove the identity and origin of the data, whether transferred electronically or in paper format. Another synonym for nonrepudiation is the digital signature, which is a technique that guarantees the authenticity and integrity of electronic documents, transactions, and communications. These synonyms are crucial in ensuring secure digital interactions and communications.