That's absolutely not true, there are tons of deeply flawed crypto systems that have been developed without any input from NSA. If you are not an expert you are virtually guaranteed to create such a flawed system.
Conversely NSA has pushed AES very hard, to the point that there are "suite B" implementations approved for safeguarding classified information. Nobody has found a backdoor in any of those.
Conversely NSA has pushed AES very hard, to the point that there are "suite B" implementations approved for safeguarding classified information. Nobody has found a backdoor in any of those.