What is a common use of digital signatures in the context of non-repudiation?

• A. To reduce the size of the data
• B. To verify the authenticity of a message or document
• C. To enhance data compression
• D. To encrypt data only

Answer: (B)

Digital signatures play a critical role in ensuring non-repudiation in digital communications and transactions. Non-repudiation is the assurance that someone cannot deny the validity of their signature on a document or a message.

In this context, digital signatures allow the recipient to verify the authenticity of a message or document by confirming that it was indeed signed by the expected sender and that it has not been altered in transit. When a sender signs a document digitally, they create a unique signature using their private key, and the corresponding public key can then be used by the recipient to verify this signature. This process establishes both the integrity of the message and the identity of the sender, thereby protecting against any claims of denial or forgery.

This function is essential in many applications, such as legal agreements, financial transactions, and secure communications, where it's crucial to establish trust and accountability between parties involved. The ability to definitively prove who signed a document and that the document remains unaltered supports the concept of non-repudiation effectively.

While the other choices involve various aspects of data handling and security, they do not directly contribute to the concept of non-repudiation like verifying the authenticity of a message or document does.