A numeric quantity formed by applying an algorithm to a message that is to be sent through a network. It is used to check that no modification of the message has taken place. The process for using a cryptographic checksum is as follows: the checksum is calculated from the message; the message is sent to some destination computer; the checksum is then encrypted and sent; the message and the checksum are both received at the destination computer; the checksum is decrypted; the destination computer recalculates the checksum using the received message and compares it with the decrypted value of the checksum that has been received; if the two checksums match, then there is a high probability that the message has not been tampered with; if they do not match, then tampering has occurred. See also checksum. A cryptographic checksum is also known as a message digest.