In article ,
pervect wrote:

Yes, another poster pointed that out, so I stand corrected. Also,
because the signals coming from the satellites are apparently spread
spectrum, it will be much less easy to reverse-engineer the codes than
I anticipated. Because we know what the output of the atomic clocks
should be, we know what the "clear" signal has to be. So I expected
extreme difficulties in encoding these signals - it's like trying to
design a good code when you have someone with access to the plaintext
working on breaking it.

Assuming that the GPS project was reasonably competent when it came to
encryption, the encryption alone should be an insurmountable challenge.
Encryption which can't be reverse-engineered (by which I mean, you can
publish everything about the system except the keys and it's still
perfectly secure) has been pretty much a solved problem for quite some
time, barring revolutionary new mathematical techniques. The only hard
part is the key distribution. So you'd have to steal a key close enough
to your launch time for that key to still be valid, and do it in such a
way that nobody catches on and changes the key sooner than usual. Having
the plaintext for a section of code text is not, afaik, very much help
when it comes to cracking modern codes.