What is the main function of non-repudiation in communications?

Non-repudiation is a fundamental principle in communications and information security that ensures that once a message or transaction has been sent and received, the sender cannot deny having sent the message, and the receiver cannot deny having received it. This principle is crucial for establishing accountability in digital communications and transactions.

By ensuring authenticity in transactions, non-repudiation provides evidence to support claims about the identity of the sender and the integrity of the message. This is commonly achieved using digital signatures, timestamps, and secure logging, which help to verify that a specific entity engaged in a particular communication or transaction. Consequently, in situations where disputes may arise, such mechanisms can serve as reliable proof, thereby fostering trust among parties involved.

The other options relate to important aspects of data management and security but do not directly pertain to the definition or function of non-repudiation. For example, data retrieval and compression are focused on how data is stored and accessed, while preventing unauthorized alteration of data pertains to data integrity and security measures rather than the concept of accountability in communication.