Divisibility and PrimesCrypto

One of the most important modern applications of prime numbers is in a field of mathematics called Cryptography. For thousands of years, people have tried to conceal messages so that only the intended recipient could read them – this is called encryption. It is used by everyone from generals exchanging secret orders during wars to personal emails or online banking details.

People always tried to come up with better, more secure encryption methods, but after some time, they were all broken using yet more advanced algorithms. In the Second World War, the German army used the Enigma: a complex machine consisting of a keyboard, rotating wheels and plugs. It encrypted messages using one of 158 million million million possibilities (that’s a 158 followed by 18 zeros!). The code was widely believed to be unbreakable, but the British Secret Service, led by mathematician Alan Turing, built some of the first computers that managed to decode it.