In cryptography, a **substitution cipher** is a method of encryption by which units of plaintext are replaced with ciphertext, according to a regular system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing an inverse substitution.

Substitution ciphers can be compared with transposition ciphers. In a transposition cipher, the units of the plaintext are rearranged in a different and usually quite complex order, but the units themselves are left unchanged. By contrast, in a substitution cipher, the units of the plaintext are retained in the same sequence in the ciphertext, but the units themselves are altered.

There are a number of different types of substitution cipher. If the cipher operates on single letters, it is termed a **simple substitution cipher**; a cipher that operates on larger groups of letters is termed **polygraphic**. A **monoalphabetic cipher** uses fixed substitution over the entire message, whereas a **polyalphabetic cipher** uses a number of substitutions at different positions in the message, where a unit from the plaintext is mapped to one of several possibilities in the ciphertext and vice versa.

Read more about Substitution Cipher: Simple Substitution, Homophonic Substitution, Polyalphabetic Substitution, Polygraphic Substitution, Mechanical Substitution Ciphers, The One-time Pad, Substitution in Modern Cryptography, Substitution Ciphers in Popular Culture

### Other articles related to "substitution cipher, cipher, ciphers":

**Substitution Cipher**s

... In a

**substitution cipher**, letters (or groups of letters) are systematically replaced throughout the message for other letters (or groups of letters) ... A well-known example of a

**substitution cipher**is the Caesar

**cipher**... To encrypt a message with the Caesar

**cipher**, each letter of message is replaced by the letter three positions later in the alphabet ...

... Atbash is a simple

**substitution cipher**for the Hebrew alphabet ... The Atbash

**cipher**for the modern Hebrew alphabet would be Plain אבגדהוזחטיכלמנסעפצקרשת

**Cipher**תשרקצפעסנמלכיטחזוהדגבא An Atbash

**cipher**for the ... This is a very simple

**substitution cipher**...

... This is just a code version of a polyalphabetic

**substitution cipher**... Polyalphabetic

**ciphers**use several different enciphering alphabets and change between them at some interval, usually after every letter ... The strength of a polyalphabetic

**cipher**comes from how many alphabets it uses to encipher, how often it switches between them, and how it switches between them ...

**Substitution Cipher**s in Popular Culture

... Sherlock Holmes breaks a

**substitution cipher**in "The Adventure of the Dancing Men" ... The Al Bhed language in Final Fantasy X is actually a

**substitution cipher**, although it is pronounced phonetically (i.e ... The Minbari's alphabet from the Babylon 5 series is a

**substitution cipher**from English ...

... Historical pen and paper

**ciphers**used in the past are sometimes known as classical

**ciphers**... They include

**Substitution cipher**the units of plaintext are replaced with ciphertext (Caesar

**cipher**and One-time pad) Transposition

**cipher**the ciphertext is a permutation of the plaintext (Rail ... Many of the classical

**ciphers**can be cracked using brute force or by analyzing only ciphertext with the exception of the one-time pad ...

### Famous quotes containing the words cipher and/or substitution:

“The eye is the first circle; the horizon which it forms is the second; and throughout nature this primary figure is repeated without end. It is the highest emblem in the *cipher* of the world.”

—Ralph Waldo Emerson (1803–1882)

“To play is nothing but the imitative *substitution* of a pleasurable, superfluous and voluntary action for a serious, necessary, imperative and difficult one. At the cradle of play as well as of artistic activity there stood leisure, tedium entailed by increased spiritual mobility, a horror vacui, the need of letting forms no longer imprisoned move freely, of filling empty time with sequences of notes, empty space with sequences of form.”

—Max J. Friedländer (1867–1958)