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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 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.
The very first well-documented description of a polyalphabetic cipher was by Leon Battista Alberti around 1467 and used a metal cipher disk to switch between cipher alphabets. Alberti's system only switched alphabets after several words, and switches were indicated by writing the letter of the corresponding alphabet in the ciphertext.
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.
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 Atbash cipher is a particular type of monoalphabetic cipher formed by taking the alphabet (or abjad, syllabary, etc.) and mapping it to its reverse, so that the first letter becomes the last letter, the second letter becomes the second to last letter, and so on. For example, the Hebrew alphabet would work like this:
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.