Signed Code?

What exacly makes sonys upgraders and popstation run on the offical fw? The signed code, what exactly is it?

Like how do you sign the code, and if sony can do it cant we do it aswell?

Think of it as a key

We cannot sign anything as we dont have this key nor the software to do it.

Well 1st we need to find the key ( as splodger said ) then we need to find the door. Sony has the key and knows where the door is lol

so do you think that if some homebrew genius found it and made hb with it all fw's could run it?

Wouldn't there be a way to reverse engineer the key? Possibly a resedue of it on the flash memory possibly? Dark Alex?
Then again, this is probably illegal as the code is sony property.