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Caesar cipher

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This is the Cryptonomicon page for Caesar cipher.

Stephensonia

*Given as a test;

19 17 17 19 14 20 23 18 19 8 12 16 19 8 3

21 8 25 18 14 18 6 31 8 8 15 18 22 18 11

is analysed into 'Attack Pearl Harbor December Seven!' by Lawrence Waterhouse's frequency analysis methodology.*

Authored entries

Community entry

The Caesar cipher is the simplest form of substitution cipher. It consists of pairing up each letter of the plaintext alphabet to a letter of the cipher alphabet.

For example (taken from The Code Book by Simon Singh, 1999)

Plaintext alphabet: a b c d e f g h i j k l m n o p q r s t u v w x y z

Ciphertext alphabet: D E F G H I J K L M N O P Q R S T U V W X Y Z A B C

Plaintext: v e n i, v i d i, v i c i

Ciphertext: Y H Q L, Y L G L, Y L F L

It is claimed the earliest known reference to this type of cipher is in the Kama Sutra, which says women should learn the art of secret writing to conceal their liasons. It was also used extensively by Julius Caesar in his military campaigns, which is why it carries his name.

This type of cipher is easily defeated by frequency analysis and is superseded by the vigenère cipher.

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