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"The Alphabet Cipher" was a brief study published by Lewis Carroll in 1868, describing how to use the alphabet to send encrypted codes. [1] It was one of four ciphers he invented between 1858 and 1868, and one of two polyalphabetic ciphers he devised during that period and used to write letters to his friends.
Another example of a polyalphabetic substitution cipher that is much more difficult to decode is the Vigenère square, an innovative encoding method. With the square, there are 26 different cipher alphabets that are used to encrypt text. Each cipher alphabet is just another rightward Caesar shift of the original alphabet.
The cipher was a type of polyalphabetic cipher known as a Variant Beaufort, using a keyword based on the Fibonacci sequence, namely AAYCEHMU. This is the reverse of the Vigenère cipher, which here enables decryption rather than encryption. Jackie Fisher, Captain R.N. 1883, later First Sea Lord 1904–1910, 1914–1915
In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet .
In a Caesar cipher, each letter of the alphabet is shifted along some number of places. For example, in a Caesar cipher of shift 3, a would become D, b would become E, y would become B and so on. The Vigenère cipher has several Caesar ciphers in sequence with different shift values.
ROT13 is a simple letter substitution cipher that replaces a letter with the 13th letter after it in the Latin alphabet. ROT13 is a special case of the Caesar cipher which was developed in ancient Rome, used by Julius Caesar in the 1st century BC. [1] An early entry on the Timeline of cryptography.
The ciphertext alphabet is rearranged according to a keyword, which then replaces the plaintext letters. K3 Cipher: This variation uses both a keyed plaintext and a keyed ciphertext alphabet, but the same keyword is used for both. K4 Cipher: Similar to the K3 Cipher, but different keywords are used for the plaintext and ciphertext alphabets.
The Alberti cipher by Leon Battista Alberti around 1467 was an early polyalphabetic cipher. Alberti used a mixed alphabet to encrypt a message, but whenever he wanted to, he would switch to a different alphabet, indicating that he had done so by including an uppercase letter or a number in the cryptogram.