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  2. Trachtenberg system - Wikipedia

    en.wikipedia.org/wiki/Trachtenberg_system

    Trachtenberg system. The Trachtenberg system is a system of rapid mental calculation. The system consists of a number of readily memorized operations that allow one to perform arithmetic computations very quickly. It was developed by the Russian engineer Jakow Trachtenberg in order to keep his mind occupied while being in a Nazi concentration ...

  3. Caesar cipher - Wikipedia

    en.wikipedia.org/wiki/Caesar_cipher

    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.

  4. Hash function - Wikipedia

    en.wikipedia.org/wiki/Hash_function

    The same technique can be used to map two-letter country codes like "us" or "za" to country names (26 2 = 676 table entries), 5-digit zip codes like 13083 to city names (100 000 entries), etc. Invalid data values (such as the country code "xx" or the zip code 00000) may be left undefined in the table or mapped to some appropriate "null" value.

  5. Vigenère cipher - Wikipedia

    en.wikipedia.org/wiki/Vigenère_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, whose increment is determined by the corresponding letter of another text, the key . For example, if the plaintext is attacking tonight and the key is ...

  6. Pigpen cipher - Wikipedia

    en.wikipedia.org/wiki/Pigpen_cipher

    The pigpen cipher (alternatively referred to as the masonic cipher, Freemason's cipher, Rosicrucian cipher, Napoleon cipher, and tic-tac-toe cipher) [2] [3] is a geometric simple substitution cipher, which exchanges letters for symbols which are fragments of a grid. The example key shows one way the letters can be assigned to the grid.

  7. Karatsuba algorithm - Wikipedia

    en.wikipedia.org/wiki/Karatsuba_algorithm

    The Karatsuba algorithm is a fast multiplication algorithm. It was discovered by Anatoly Karatsuba in 1960 and published in 1962. [1] [2] [3] It is a divide-and-conquer algorithm that reduces the multiplication of two n -digit numbers to three multiplications of n /2-digit numbers and, by repeating this reduction, to at most single-digit ...

  8. Substitution cipher - Wikipedia

    en.wikipedia.org/wiki/Substitution_cipher

    t. e. 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 ...

  9. Code (cryptography) - Wikipedia

    en.wikipedia.org/wiki/Code_(cryptography)

    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 ...