What do they use these large prime numbers for? I think I heard one time it was something to do with encryption but if so how does it work? Or is it just for fun?

Edit - I looked it up and it seems encryption is based on the product of 2 large primes (public key) and the primes themselves (private key) but seeing as how 128 bit encryption already yields 3,835,341,275,459,350,000,000,000,000,000,000,000 different prime numbers which would take a computer 121,617,874,031,562,000 years to crack why bother looking for bigger ones or do primes have other uses?

Speaking of which why isn't '1' a prime number any more? It used to be. As all other non-prime numbers except '1' are composite numbers it seems unfair to cast the number '1' out into no-man's land.

I don't have any reference at hand, but I think this information must be outdated. 512 bits key can be breaken in a reasonable time - it was done for the first time not later than in 2000.

I think that we should move on from prime numbers to something more interesting.

Maybe morphing a code with a similar concept to Arnold's Cat Map. That would be fun. (unless they already have done that in which case I just feel stupid).