What term describes the assurance that a sender cannot deny sending a message nor can the recipient deny receiving it?

The concept described in the question is nonrepudiation. Nonrepudiation refers to a guarantee that someone cannot deny the validity of their signature on a document or the sending of a message. This is especially important in digital communications and transactions, where it ensures that both the sender of a message and the recipient have proof of the message being sent and received. It typically involves the use of cryptographic techniques, such as digital signatures, which provide evidence that a specific person or entity sent a message, as well as confirmation that the intended recipient received it.

In the context of cloud security and information systems, nonrepudiation is critical for maintaining accountability and trust in communications. For example, in financial transactions or legal agreements, nonrepudiation helps prevent disputes by providing irrefutable evidence of who took specific actions and when.

Integrity refers to the assurance that data has not been altered or tampered with, confidentiality ensures that information is protected from unauthorized access, and availability guarantees that information is accessible to authorized users when needed. While these concepts are vital for a secure environment, they do not address the specific issue of denial of sending or receiving messages, which is core to the definition of nonrepudiation.