[huxley]

To clear up my own confusion, the 56 bytes only comes in when using bcrypt for encrypting vs hashing, however the "72 character" password limit for hashing is actually 18 words of 32-bits.

http://www.gossamer-threads.com/lists/wiki/wikitech/430719#4...

"Note that much confusion on the web about key lengths with bcrypt ('72' vs. '56' bytes) comes from the fact that there are TWO algorithms called 'bcrypt' which both happen to use Blowfish. One is an encryption algorithm, and the other is a hash algorithm. While they share a common core component, the purposes are thereby entirely different. For the sake of the bcrypt HASHING/key-strengthening algorithm (which we care about now), the 72-byte input parameter is in no way a theoretical problem at all, even for non-Latin UTF-8 based passphrases which eat up 3 bytes per unicode point. The reason is because the text-based passphrase itself needs to 'somehow' be converted into 18 words of 32-bits each anyway. (If we were _encrypting_ then the 56 bytes limit for THAT algorithm would come into play.) Even if you restrict your attention to ASCII it would not be ideal to simply convert ASCII code points to a (zero-padded) juxtaposed stream of 32-bit chunks anyway, because, well for one thing, you would be throwing away entropy due to not using the upper 1-bit range in each char, not to mention the range of unavailable non-printable ASCII characters."