What does non-repudiation ensure in network security?

• A. That data is encrypted during transit
• B. That a person/system cannot deny their actions
• C. That certificates are valid
• D. That public keys remain confidential

Answer: (B)

Non-repudiation is a crucial concept in network security that ensures a person or system cannot deny their involvement in a transaction or the actions they have taken. This is achieved through mechanisms that provide proof of the origin and integrity of the data, often using digital signatures and cryptographic techniques. By employing these methods, both parties in a communication can be assured that once a transaction has been completed or a message has been sent, the sender cannot later claim they did not send it or take a certain action.

This principle is vital for maintaining trust in digital communications, especially in legal and financial contexts where accountability is paramount. It protects against disputes regarding who initiated a transaction or modified data, thereby strengthening the overall security posture of the network. In contrast, the other choices focus on different aspects of security, such as encryption, the validity of certificates, and confidentiality of keys, which, while important, do not directly pertain to the concept of non-repudiation.