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Tabula recta. In cryptography, 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 the German author and monk Johannes Trithemius [1] in 1508, and used in his Trithemius ciph
The Vigenère square or Vigenère table, also known as the tabula recta, can be used for encryption and decryption. 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 ...
Each alphabet was shifted one letter to the left from the one above it, and started again with A after reaching Z (see table). Tabula recta. Trithemius's idea was to encipher the first letter of the message using the first shifted alphabet, so A became B, B became C, etc.
A tabula recta for use with an autokey cipher An autokey cipher (also known as the autoclave cipher ) is a cipher that incorporates the message (the plaintext ) into the key . The key is generated from the message in some automated fashion, sometimes by selecting certain letters from the text or, more commonly, by adding a short primer key to ...
"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.
In the Vigenère cipher, the first row of the tableau is filled out with a copy of the plaintext alphabet, and successive rows are simply shifted one place to the left. (Such a simple tableau is called a tabula recta, and mathematically corresponds to adding the plaintext and key letters, modulo 26.) A keyword is then used to choose which ...
Modern variants of the running key cipher often replace the traditional tabula recta with bitwise exclusive or, operate on whole bytes rather than alphabetic letters, and derive their running keys from large files. Apart from possibly greater entropy density of the files, and the ease of automation, there is little practical difference between ...
Before the modern era, cryptography focused on message confidentiality (i.e., encryption)—conversion of messages from a comprehensible form into an incomprehensible one and back again at the other end, rendering it unreadable by interceptors or eavesdroppers without secret knowledge (namely the key needed for decryption of that message).