If you have your key management worked out properly, reading, tampering, and impersonation are more or less minimized as risks. By that, I mean that it would probably take a major power like the former Soviet Union lots of resources and effort to accomplish it.

NSA wanted us to build a cryptographic implement for them about 20 years ago, because FIPS-46, which was then used by banks to encrypt funds transfers, used too much of their time and computer resources to track FIPS-46 encoded electronic funds transfers, which they needed to do in order to "follow the money" in various contexts. That was back when supercomputers ran at a very few MegaFlops. It's a long story ...

RE