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A stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream . In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream.
However, generally they are considerably slower (typically by a factor 2–10) than fast, non-cryptographic random number generators. These include: Stream ciphers. Popular choices are Salsa20 or ChaCha (often with the number of rounds reduced to 8 for speed), ISAAC, HC-128 and RC4. Block ciphers in counter mode.
For example, squaring the number "1111" yields "1234321", which can be written as "01234321", an 8-digit number being the square of a 4-digit number. This gives "2343" as the "random" number. Repeating this procedure gives "4896" as the next result, and so on. Von Neumann used 10 digit numbers, but the process was the same.
The random numbers in the keystream then have to be at least between 0 and 25. To encrypt we add the keystream numbers to the plaintext. And to decrypt we subtract the same keystream numbers from the ciphertext to get the plaintext. If a ciphertext number becomes larger than 25 we wrap it to a value between 0-25.
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The CBS Evening News is a daily evening broadcast featuring news reports, feature stories and interviews by CBS News correspondents and reporters covering events around the world. The program has been broadcast since July 1, 1941, under the original title CBS Television News , eventually adopting its current title in 1963.
Truly random, as opposed to pseudorandom, one-time pad values, which is a non-trivial requirement. Random number generation in computers is often difficult, and pseudorandom number generators are often used for their speed and usefulness for most applications. True random number generators exist, but are typically slower and more specialized.
Salsa20 and the closely related ChaCha are stream ciphers developed by Daniel J. Bernstein.Salsa20, the original cipher, was designed in 2005, then later submitted to the eSTREAM European Union cryptographic validation process by Bernstein.