> Encryption algorithms are deterministic. If you implement a known good algorithm on your own, and it gets the same outputs given the same inputs, then you are

> Encryption algorithms are deterministic. If you implement a known good algorithm on your own, and it gets the same outputs given the same inputs, then you are highly unlikely to shoot yourself in the foot. This is not what people are talking about when they warn not to roll your own crypto. That is exactly what people mean by "don't roll your own crypto." If your belief is that you only need to match the same output per input, then your implementation might be an oracle that leaks information. Crypto people don't say this for job security or to feel important. They say it, because they, themselves, have made mistakes, and they constantly see examples of programs that trivialize both security and cryptography while simultaneously introducing foreseeable bugs and obviously weak crypto.