Despite it being a fairly complicated machine with many gears, keys and lights, it still used just a series of substitution ciphers one after another to encode messages. By shifting the ciphers by one letter each time a new letter was encoded, the builders of the machine were able to minimize the chance that the frequency of certain letters appearing in the code could be used to break it. The introduction of computers has revolutionized crytography. Computers can also be used to break codes that in the past might have seemed unbreakable. So far, it is far easier for a computer to encrypt a message than to break it.
Encryption is no longer the business of just government and spies.
The ability to safely encrypt communications is very important to anyone who uses the internet. When somebody purchases from an on-line store, they use a credit card number. Using the type of ciphers we've discussed so far, this would be very difficult to do. The cipher they use would need a key. The solution lies with a type of cipher that can do what is known as public key encryption .