Why is the hashing function critical for non-repudiation?

The hashing function is critical for non-repudiation primarily because it ensures message integrity and facilitates the use of digital signatures. Non-repudiation refers to the assurance that someone cannot deny the validity of their signature on a document or a message.

When a sender creates a digital signature, they typically hash the message and then encrypt that hash with their private key. This process provides a unique fingerprint of the message. If the message were altered in any way, the hash would change, indicating that the integrity of the message has been compromised. This allows the recipient to verify that the message is indeed from the claimed sender and that it has not been tampered with.

Additionally, digital signatures rely on hashing functions to create a strong link between the signatory and the content of the message, which is fundamental in proving the authenticity and integrity of communications. Thus, through this combination of hashing and encryption, a robust framework for non-repudiation is established, ensuring that the sender cannot later deny having sent the message.

The other options, while related to security processes, do not directly address the relationship between hashing, message integrity, and non-repudiation as effectively as the correct option does.