A cryptographic checksum is a mathematical value (called a checksum) that is assigned to a file and used to "test" the file at a later date to verify that the data contained in the file has not been maliciously changed. A cryptographic checksum is created by performing a complicated series of mathematical operations (known as a cryptographic algorithm) that translates the data in the file into a fixed string of digits called a hash value, which is then used as a checksum. Without knowing which cryptographic algorithm was used to create the hash value, it is highly unlikely that an unauthorized person would be able to change data without inadvertently changing the corresponding checksum. Cryptographic checksums are used in data transmission and data storage.
Cryptographic checksums are also known as message authentication codes, integrity check-values, modification detection codes, or message integrity codes.