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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 .
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 Caesar cipher is an Affine cipher with a = 1 since the encrypting function simply reduces to a linear shift. The Atbash cipher uses a = −1 . Considering the specific case of encrypting messages in English (i.e. m = 26 ), there are a total of 286 non-trivial affine ciphers, not counting the 26 trivial Caesar ciphers.
The Vigenère cipher has several Caesar ciphers in sequence with different shift values. To encrypt, a table of alphabets can be used, termed a tabula recta , Vigenère square or Vigenère table . It has the alphabet written out 26 times in different rows, each alphabet shifted cyclically to the left compared to the previous alphabet ...
ROT13 is a Caesar cipher, a type of substitution cipher.In ROT13, the alphabet is rotated 13 steps. Substitution of single letters separately—simple substitution—can be demonstrated by writing out the alphabet in some order to represent the substitution.
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.
Alphabet shift ciphers are believed to have been used by Julius Caesar over 2,000 years ago. [6] This is an example with k = 3 . In other words, the letters in the alphabet are shifted three in one direction to encrypt and three in the other direction to decrypt.
A key could be used to reorder the alphabet in the square, with the letters (without duplicates) of the key being placed at the beginning and the remaining letters following it in alphabetical order. [2] For example, the key phrase "polybius cipher" would lead to the reordered square below.