[relaxnow]

Don't forget that it should ideally be cryptographically random. If the sequence is predictable (like based on an auto incrementing number or on time) then you might still be able to guess a 256-bit number.

[wtbob]

> Don't forget that it should ideally be cryptographically random.

I thought that went without saying, nut yes, it must be cryptographically random (not ideally—it must be).