An interesting bit of math
http://plus.maths.org/content/os/issue26/features/sautoy/index
Every time you use your credit card on the internet to buy a ticket to see Real Madrid play, your account is kept secret from hackers thanks to the power of prime numbers. Prime numbers have become the locks that preserve the secrets that are racing through the electronic shopping mall.
Each e-business chooses two big primes, p and q, which they keep secret. The product of these primes, N=pxq, is made public. A calculation using N encrypts your credit card, but the only way to undo the calculation and decrypt the secret message is to know the secret primes p and q. Cracking codes is the same as cracking the public number N into its prime building blocks. It’s a bit like a chemist who wants to know the atoms inside a compound. Although chemists have solved their problem, mathematicians lack any fast way to do this prime-number spectroscopy – to the relief of internet cryptographers.






