In reference to digital security, nonrepudiation means to ensure that a transferred message has been sent and received by the parties claiming to have sent and received the message. Nonrepudiation is a way to guarantee that the sender of a message cannot later deny having sent the message and that the recipient cannot deny having received the message.
Nonrepudiation can be obtained through the use of:
digital signatures -- function as a unique identifier for an individual, much like a written signature.
confirmation services -- the message transfer agent can create digital receipts to indicated that messages were sent and/or received.
timestamps -- timestamps contain the date and time a document was composed and proves that a document existed at a certain time.
