[cryptography] Oddity in common bcrypt implementation

Steven Bellovin smb at cs.columbia.edu
Tue Jun 28 13:48:37 EDT 2011

> Wow, this sounds a lot like the way 64-bit DES was weakened to 56 bits.
It wasn't weakened -- parity bits were rather important circa 1974.
(One should always think about the technology of the time.  The
initial and final permutations were rightly denounced as cryptographically
irrelevant (though it isn't clear that that would be true in a secret
design; the British had a lot of trouble until they figured out the
static keyboard map of the Enigma), but they weren't there for
cryptographic reasons; rather, they were an artifact of a
serial/parallel conversion.

		--Steve Bellovin, https://www.cs.columbia.edu/~smb

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