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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.
History of cryptography. Cryptography, the use of codes and ciphers to protect secrets, began thousands of years ago. [ 1] Until recent decades, it has been the story of what might be called classical cryptography — that is, of methods of encryption that use pen and paper, or perhaps simple mechanical aids.
However, in cryptography, code has a more specific meaning: the replacement of a unit of plaintext (i.e., a meaningful word or phrase) with a code word (for example, "wallaby" replaces "attack at dawn"). A cypher, in contrast, is a scheme for changing or substituting an element below such a level (a letter, a syllable, or a pair of letters, etc ...
Code (cryptography) A portion of the "Zimmermann Telegram" as decrypted by British Naval Intelligence codebreakers. The word Arizona was not in the German codebook and had therefore to be split into phonetic syllables. Partially burnt pages from a World War II Soviet KGB two-part codebook. In cryptology, a code is a method used to encrypt a ...
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 ...
World War I cryptography. With the rise of easily-intercepted wireless telegraphy, codes and ciphers were used extensively in World War I. The decoding by British Naval intelligence of the Zimmermann telegram helped bring the United States into the war. Trench codes were used by field armies of most of the combatants (Americans, British, French ...
The export of cryptography from the United States to other countries has experienced various levels of restrictions over time. [2] World War II illustrated that code-breaking and cryptography can play an integral part in national security and the ability to prosecute war. Changes in technology and the preservation of free speech have been ...
Kerckhoffs viewed cryptography as a rival to, and a better alternative than, steganographic encoding, which was common in the nineteenth century for hiding the meaning of military messages. One problem with encoding schemes is that they rely on humanly-held secrets such as "dictionaries" which disclose for example, the secret meaning of words.