Hash is an identifying value that is used to verify the data integrity of messages transmitted over a computer network. The sending computer uses a secret algorithm that computes the value for the message. This value constitutes, in effect, a digital fingerprint for the message because the value is uniquely a product of the message’s content.
Also, the hashing algorithm cannot be derived from the message content or value. The message and the value are then transmitted. The receiving computer, which also knows the secret algorithm, performs the same computation on the message. If the resulting value does not agree with the value received from the sending computer, then it is proved that the message was altered en-route, and the message is discarded. See one-way function.
