Repudiation is the rejection or denial of something as valid or true. Non-Repudiation is assuring that something that actually occurred cannot be claimed as having not occurred. A security service that provides this protection can be one of two types:

• One in which the recipient of the data gets and stores information proving that the data came from the originator. This blocks the originator from claiming they never sent the data.
• One in which the sender of the data gets confirmation that the data was received by the recipient as intended.