"If you're going to be writing cryptographic code, and you're not sure what you're doing,
just put the keyboard away and ask someone qualified to write it for you. For all our sakes."
- Bacterius, 2013
Or, really, the more general statement - if your code is going to be used in situations where it failing could have very real consequences, don't write the code if you cannot assume said consequences. Seriously, the Dunning-Kruger effect is omnipresent in the field of programming, and not taking it into account is a recipe for disaster. See the recent utter failure of the Mega file sharing website's launch - the developer had no clue what he was doing, and the result is painfully obvious and predictable.
I'm writing cryptographic code and I'm not 100% sure what I'm doing. Should be interesting LOL