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9

Parity of DES key bytes was introduced on request of US authorities during the design of DES in the late 1970s: it mitigates the risk of accidental key alteration; in particular, any all-zeros or all-ones byte of the key is rejected by the mandatory odd parity check, and any one-bit alteration is caught, which are advantages from a functionality ...


7

They are there to check if the key was indeed correctly retrieved. It could for instance be that the key is a result of key decryption or key agreement. In that case, or simply during transmission, wrong keys are used. According to NIST FIPS 46-3: The 8 error detecting bits..." Or even better, Wikipedia states ANSI INCITS 92-1981), section 3.5: One ...



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