> Or if the big computer says "this entire Debian distribution of binary files was indeed compiled with this version of GCC", you can quickly verify that all the binaries are exactly what they should be - without having to trust anyone.

> So amazed and intrigued that I had to learn how it's done

Any chance you could just illustrate this somehow with a basic example? I just don't see how you could possibly verify that a program is produced with GCC without going through approximately as much effort as it'd take to compile it.