Checksums and Error Control
- Pp. 191-218 (28)Peter Fenwick
Much computer data is prone to errors, especially when transmitted in space (or in time, as in data storage). The corresponding need for error detection and correction has been recognised from the very beginning of electrical computation. Error correction is a large and complex subject which is just touched-on here, but error detection is a much simpler, but seldom discussed subject and is the main emphasis of this chapter. After a brief mention of parity checks in textual data transmission, the emphasis is on checksums for verifying strings of decimal digits. Check-digit algorithms include the Luhn, those used in ISBN codes, and the Verhoe and Damm checks, both based on advanced number theory. The chapter concludes with discussion of the more-powerful message checksums, especially those of Fletcher and Adler, and the Cyclic Redundancy checks.