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Caesar Cipher

I was thinking about cryptography today as part of a short talk I gave to introduce a meeting at lunchtime, where I revisited what is known as the Caesar cipher. It is an elementary way of hiding the content of a message by replacing each letter with one three places higher (or some other shift – ROT-13, or moving halfway through the alphabet, is probably the most well-known modern version) and is named after Julius Caesar who, according to Suetonius, used it to encipher sensitive communications.

It can be broken with pen and paper and really isn’t suitable for any modern application other than a game to introduce the subject of encryption. However, it illustrates two things; firstly that it is a long-standing axiom that knowledge is power and secondly that, in the present age, we’ve got to go a long way beyond what was good enough for Caesar if we want to keep our data safe.

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