In cryptography

Cryptography

Cryptography is the practice and study of techniques for secure communication in the presence of third parties...

, the tabula recta (from Latin tabula rēcta) is a square table of alphabets, each row of which is made by shifting the previous one to the left. The term was invented by Johannes Trithemius

Johannes Trithemius

Johannes Trithemius , born Johann Heidenberg, was a German abbot, lexicographer, historian, cryptographer, polymath and occultist who had an influence on later occultism. The name by which he is more commonly known is derived from his native town of Trittenheim on the Mosel in Germany.-Life:He...

 in 1508, and used in his cipher

Trithemius cipher

The Trithemius cipher is a polyalphabetic cipher invented by the German author and monk Johannes Trithemius in the 15th century. The cipher was published in his book Polygraphia, which is credited with being the first published work on cryptology. It uses a letter square with the 26 letters of the...

.

Trithemius used the tabula recta to define a polyalphabetic cipher

Polyalphabetic cipher

A polyalphabetic cipher is any cipher based on substitution, using multiple substitution alphabets. The Vigenère cipher is probably the best-known example of a polyalphabetic cipher, though it is a simplified special case...

 which was equivalent to Leon Battista Alberti's cipher disk

Alberti cipher disk

thumb|right|250px|A Treatise on Ciphers. The Alberti Cipher Disk.The Alberti cipher disk, also called formula, is a cipher disc which was described by Leon Battista Alberti in his treatise De Cifris of 1467...

 except that the alphabets are not mixed. The tabula recta is often referred to in discussing pre-computer ciphers, including the Vigenère cipher

Vigenère cipher

The Vigenère cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword. It is a simple form of polyalphabetic substitution....

 and Blaise de Vigenère

Vigenère

Vigenère may refer to:*Blaise de Vigenère, a 16th-century French cryptographer*The Vigenère cipher, a cipher whose invention was later misattributed to Vigenère...

's less well-known autokey cipher

Autokey cipher

An autokey cipher is a cipher which incorporates the message into the key. There are two forms of autokey cipher: key autokey and text autokey ciphers. A key-autokey cipher uses previous members of the keystream to determine the next element in the keystream...

. All polyalphabetic ciphers based on Caesar cipher

Caesar cipher

In cryptography, a Caesar cipher, also known as a 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...

s can be described in terms of the tabula recta.

In order to encrypt a plaintext, one locates the row with the first letter to be encrypted, and the column with the first letter of the key. The letter where the line and column cross is the ciphertext letter.