Tornado code: Difference between revisions

Revision as of 23:26, 13 May 2008

Revision as of 22:28, 28 May 2008

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== Rough Overview ==

Tornado codes work via xor (exclusive or). Xor operates on binary values, 1s and 0s. A xor B is 1 if A and B are thehave different values and 0 if A and B arehave differentthe same values. If you are given (A xor B) and A, you can determine the value for B. (Note that A xor B xor A is equal to B.) Similarly, if you are given (A xor B) and B, you can determine the value for A. This extends to multiple values, so given (A xor B xor C xor D) and any 3 of the values, the missing value can be recovered.

The xor of a number of binary variables is called their "parity" and this is often used in error detection and correction. Tornado codes use it for error correction. They use another checksum (like CRC-32 or MD5) for error detection.