What concept ensures that a sender cannot deny sending a message once it is digitally signed?

Nonrepudiation is a key concept in digital communications that ensures a sender cannot deny having sent a message after it has been digitally signed. This is achieved through digital signatures, which not only verify the identity of the sender but also confirm that the message has not been altered during transmission.

When a message is digitally signed, it is protected by cryptographic algorithms that bind the identity of the sender to the message content. This binding creates a form of accountability, whereby if the sender attempts to deny sending the message, the digital signature provides irrefutable proof that they did. Essentially, nonrepudiation provides a way to verify the authenticity of a communication and serves as a safeguard against possible disputes regarding whether a specific message was sent by a particular individual or entity.

In contrast, confidentiality relates to keeping information secret from unauthorized users, integrity involves ensuring that the message remains unchanged during its transit, and encryption is the process of converting information into a coded format to prevent unauthorized access. While these concepts are important in securing communications, they do not address the issue of denial of sending a message, which is specifically covered by nonrepudiation.