Well it depends on what you mean by backdoor. Just to pick one... let's take AES. There are a lot of open-source implementations, depending on your platform. Al

Well it depends on what you mean by backdoor. Just to pick one... let's take AES. There are a lot of open-source implementations, depending on your platform. Almost all of them are open-source [0]. Furthermore, AES is based on the Rijndael cipher [1], which is simply a mathematical process that an undergrad could understand and implement. Ignoring the fact that the major implementations have been poured over and audited by many researchers (and that you could do the same), it'd be just too risky to put a backdoor into an open implementation. It might be possible that the NSA has discovered some side-channel attack [2]. If that's what you mean by backdoor, then I suppose you could be right. (Perhaps every CPU has been manufactured so as to facilitate timing attacks.) I still think that the probabilities combine to some astronomically low number because those attacks still take time, and I don't think they have the computational ability to simultaneously run attacks against any very large subset of the US population. I don't trust secret, unaccountable organizations... but it just seems too extraordinary to imagine that any organization could actively monitor billions (millions, even) of communication streams at a time. [0] http://en.wikipedia.org/wiki/AES_implementations http://en.wikipedia.org/wiki/AES_implementations [1] http://csrc.nist.gov/archive/aes/rijndael/Rijndael-ammended.pdf#page=1 http://csrc.nist.gov/archive/aes/rijndael/Rijndael-ammended.... [2] http://en.wikipedia.org/wiki/Side-channel_attacks http://en.wikipedia.org/wiki/Side-channel_attacks