I'm not sure that's so clear. First of all, you don't have to do it to every message. You first run a very cheap test of the message to see if it appears to con

I'm not sure that's so clear. First of all, you don't have to do it to every message. You first run a very cheap test of the message to see if it appears to consist of normal language. Only if this test fails do you run through a (still very cheap) battery of common and primitive enciphering techniques. Yes, there are lots of emails, but most of them are short, and the kind of processing we're doing here is incredibly fast. And sure, this wouldn't work against steganography, but anybody who knows about steganography probably also knows how to do proper encryption that the NSA won't be able to break.