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Book cipher. The King James Bible, a highly available publication suitable for the book cipher. A book cipher is a cipher in which each word or letter in the plaintext of a message is replaced by some code that locates it in another text, the key . A simple version of such a cipher would use a specific book as the key, and would replace each ...
Classical cipher. In cryptography, a classical cipher is a type of cipher that was used historically but for the most part, has fallen into disuse. In contrast to modern cryptographic algorithms, most classical ciphers can be practically computed and solved by hand. However, they are also usually very simple to break with modern technology.
Four-square cipher. The four-square cipher is a manual symmetric encryption technique. [1] It was invented by the French cryptographer Felix Delastelle . The technique encrypts pairs of letters ( digraphs ), and thus falls into a category of ciphers known as polygraphic substitution ciphers. This adds significant strength to the encryption when ...
Step-by-step process for the double columnar transposition cipher. In cryptography, a transposition cipher (also known as a permutation cipher) is a method of encryption which scrambles the positions of characters ( transposition) without changing the characters themselves. Transposition ciphers reorder units of plaintext (typically characters ...
Letter frequency is the number of times letters of the alphabet appear on average in written language. Letter frequency analysis dates back to the Arab mathematician Al-Kindi ( c. 801 –873 AD), who formally developed the method to break ciphers. Letter frequency analysis gained importance in Europe with the development of movable type in 1450 ...
The Vigenère cipher is named after Blaise de Vigenère (pictured), although Giovan Battista Bellaso had invented it before Vigenère described his autokey cipher. The Vigenère cipher ( French pronunciation: [viʒnɛːʁ]) is a method of encrypting alphabetic text where each letter of the plaintext is encoded with a different Caesar cipher ...
In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; 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 ...
In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption —a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code", as ...