Which of the following best defines the term 'Non-repudiation'?

Non-repudiation refers to the assurance that someone cannot deny the validity of their signature on a document or the sending of a message. It provides proof of the origin, integrity, and reception of data, which means that the sender cannot later claim they did not send the message or that the message was tampered with in transit. This concept is crucial in various fields, especially in electronic communications and transactions, as it establishes accountability for actions taken.

The other definitions focus more on distinct aspects of data security. Ensuring confidentiality pertains to keeping data secret and accessible only to authorized parties. Maintaining integrity relates to ensuring that data is accurate and unaltered during its transmission. Guaranteeing authenticity deals with verifying the identity of the sender or the origin of the information. While these aspects are essential components of a comprehensive security policy, they do not encapsulate the full scope of non-repudiation, which is fundamentally about preventing denial regarding the transmission of messages.