> At the risk of invoking Cunningham's Law, nobody uses passphrases anywhere near 64 bytes that he / she has to memorize.

http://52.24.230.241/bc/password_generation.php

This produces memorable passphrases pretty close to that limit, as described in http://www-scf.usc.edu/~mghazvin/papers/marjan15.pdf

Password yes, passphprase it's quite possible.

Eh, Materialistic doesn't allow me to edit my comment. I mean you're right about passwords, but a passphrases (e.g. a sentences) are easy to remember, more secure and can often be longer than 64 bytes.

Er, of course it's not a coincidence; hex is base 16, so it takes 4 bits to represent each digit, which is half a byte. That is, hex always is 2 digits per byte.

Or did I miss your point?