Phil Karn:
if they find "readdat.exe" on your PC, disassemble it and discover that it's a program to extract and decrypt ciphertext from DAT tapes, you're in trouble. And if you encrypt your copy of "readdat.exe", well, you now need a plaintext decryption program to decrypt THAT.
Perhaps some hacks (ab)used by virus writers might be useful here. We might hide "readdat.exe" inside a larger "innocuous.exe" and scramble it with the "mutation engine", which creates a unique signature for each copy of readdat.exe's code (including the engine itself, which bootstraps from a very short common code sequence). The result is they have no signature to search for, even if they already have a copy of "readdat.exe" and the mutation engine. Nick Szabo szabo@techbook.com