The wiki article on GPS encryption seems to say that stealing the key for one satellite is possible (720 gigabytes), but the master key at 26 terabytes seems slightly harder to sneak out in an email or USB key. Of course I'm a wiki expert on this, so someone with actual knowledge could probably be more informative.
Those are just the sizes of the pseudorandom sequences produced by a PRNG. They'll be defined by structures much smaller than that. However, that's not the bit that needs stealing, and doesn't even strictly need to be secret.
