“they couldn’t break computationally,”
“Massive though their resources are, they don’t have the computing power to do that. “
I wouldn’t be so hasty as to say that. First, not everyone will use such a system. Second, for the very few that do, they’ve got all the computing and crypto power they need.
Well then, we’ll just need to see to it that end-to-end public-key encryption for e-mail becomes the de facto standard.
In the meantime, I’m hoping someone makes an improvement on ScareMail, that instead of appending pseudo-English text full of words selected from the DHS keyword list, appends the text, “If you were expecting an encrypted message from me, it is in the first attachment,” to every e-mail, automatically creates a first attachment with at random an encrypted version of a file from a user-specified folder, an encrypted message about the Fourth Amendment, or a file of random bits (with the encryption chosen at random from a selection of different algorithms with a (pseudo-)random key for the first two options), then allows the user to substitute a real encrypted message if he wants.
If I had modern coding skills I’d work on it myself, but I don’t think an app programmed in Fortran, Pascal or LISP would cut it these days.