What does nonrepudiation ensure in a communication process?

Nonrepudiation is a foundational concept in information security that ensures both parties in a communication process can confirm the authenticity of the message and their involvement in the communication. This means that neither the sender nor the receiver can deny their actions regarding the message.

In practical terms, this is often achieved through mechanisms such as digital signatures, which provide a secure way to verify the identity of the sender and ensure that the content of the message has not been tampered with. If the sender signs a message digitally, they cannot later claim that they did not send it, and likewise, the recipient cannot deny having received it if it is properly documented.

The other choices reflect misunderstandings of nonrepudiation. For instance, claiming that the sender can deny sending a message or the receiver can claim they did not receive it contradicts the principles of nonrepudiation. The statement about message alteration pertains to integrity rather than nonrepudiation, which mainly deals with accountability of actions taken by both parties in the communication process. Thus, nonrepudiation serves to provide both security and accountability in communications, solidifying trust between the parties involved.