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In the history of cryptography, the Nihilist cipher is a manually operated symmetric encryption cipher, originally used by Russian Nihilists in the 1880s to organize terrorism against the tsarist regime. The term is sometimes extended to several improved algorithms used much later for communication by the First Chief Directorate with its spies.
Stream ciphers, in contrast to the 'block' type, create an arbitrarily long stream of key material, which is combined with the plaintext bit-by-bit or character-by-character, somewhat like the one-time pad. In a stream cipher, the output stream is created based on a hidden internal state that changes as the cipher operates.
Later Vula added a stream cipher keyed by book codes to solve this problem. [ 36 ] A related notion is the one-time code —a signal, used only once; e.g., "Alpha" for "mission completed", "Bravo" for "mission failed" or even "Torch" for " Allied invasion of French Northern Africa " [ 37 ] cannot be "decrypted" in any reasonable sense of the word.
In practice, a message this short and with a predictable keyword would be broken almost immediately with cryptanalysis techniques. Transposition ciphers have several vulnerabilities (see the section on "Detection and cryptanalysis" below), and small mistakes in the encipherment process can render the entire ciphertext meaningless.
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 .
The Aristocrat Cipher is a type of monoalphabetic substitution cipher in which plaintext is replaced with ciphertext and encoded into assorted letters, numbers, and symbols based on a keyword. The formatting of these ciphers generally includes a title, letter frequency, keyword indicators, and the encoder's nom de plume . [ 1 ]
The distribution of grilles, an example of the difficult problem of key exchange, can be eased by taking a readily-available third-party grid in the form of a newspaper crossword puzzle. Although this is not strictly a grille cipher, it resembles the chessboard with the black squares shifted and it can be used in the Cardan manner.
The National Cipher Challenge is an annual cryptographic competition organised by the University of Southampton School of Mathematics. Competitors attempt to break cryptograms published on the competition website. [ 1 ]