Advanced Placement (AP) Computer Science

What principle ensures users cannot dispute having sent a message?

1. Integrity

2. Non-repudiation

3. Confidentiality

4. Authentication

The correct answer is: Non-repudiation

The principle that ensures users cannot dispute having sent a message is non-repudiation. Non-repudiation is a key concept in the realm of digital security and communications, which provides a way to ensure that a sender cannot deny having sent a specific message. This is often achieved through the use of digital signatures or cryptographic techniques that bind a message to its sender in a secure manner. When a message is digitally signed, it creates a unique fingerprint of that message which is linked to the sender's private key. This digital signature verifies both the identity of the sender and the integrity of the message. As a result, if the sender later claims they did not send the message, the presence of the digital signature acts as proof that they did indeed send it, thus preventing repudiation. In contrast, the other principles serve different purposes. Integrity ensures that data has not been altered in transit. Confidentiality focuses on keeping the message secret from unauthorized parties. Authentication verifies the identity of users involved in a communication. While all these concepts are important in the field of cybersecurity, it is non-repudiation that specifically addresses the issue of denying a sent message.