Introduction to Encryption

Introduction to Encryption

Introduction The Shorter Oxford English Dictionary lists the 5th meaning of the word cipher as, “A secret manner of writing by any of various methods, intelligible only to those possessing the key (1528).” Encryption, the use of ciphers, is not new. Far from it. It has been with us for a very long time. I used to say that encryption was traditionally for the four P’s. Princes, Popes, Purveyors and Paramours, since they were the people who had secrets and needed to keep them. Julius Caesar used encryption to send his instructions to his armies, and the Caesar cipher, one of the earliest recorded ciphers, is named after him. But the honours for the groundwork to our modern use of cryptography should probably go to the Turkish community for their application of mathematical algorithms (formulae to convert by a mathematical process between ordinary information, called plaintext by the cryptography community, and cipher text, the encrypted information that is impossible to understand without the key) to automate and make routine the business of encrypting and decrypting information. When Mary, Queen of Scots sent her encrypted messages to raise a revolt against Elizabeth I, the process was very manual, and slow. It took Elizabeth’s code breaker some weeks to figure out what the secret information meant. By comparison, by the time the Germans introduced their Enigma machines (and subsequently the British their computers at Bletchley Park to decrypt them) the process was becoming fully automated, and down to days or just hours. Today, every PC is equipped with enough powerful mathematically proven encryption engines to process information at many megabytes per minute – something beyond the wildest dreams of our ancestors, and little realised by most PC users.

Why use encryption? Most often, to keep secrets. Everyone has a need to keep some things secret. The operating system has secrets it needs to keep away from users, users want their credit card details kept secret and away from hackers, everyone wants their financial and health affairs secret, and, sadly, it appears that even today people still need to keep their religious persuasions secret. It is unfortunate, but the need to keep a wide variety of information secret also means that people can also use encryption to keep secret things that society has decided are unlawful, such as the plans to rob a bank. Encryption technologies also have other valuable capabilities. Any attempt to falsify the content of an encrypted message will cause failure during decryption. This was not the case with the Caesar cipher, where each letter was transformed separately from every other letter, so altering one or more letters might well not be noticed by the recipient.

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