@golgaloth I guess the quicker way to say it is this:
There are some parts of how the internet work where certain, trusted, companies have super-secret numbers they do fancy math with to let you know it's them say "you can trust this computer because you trust me!"
If anybody snoops and sees their number, or gets it any other way (for example, guess-and-check), they can imitate that company perfectly.
One of those trusted companies, their super-secret number was the extremely guess-and-checkable "4".