Boolean functions play a central role in the design of most symmetric cryptosystems and in their security. In stream ciphers, they are usually used to combine the outputs to several linear feedback shift registers (see the corresponding entry and Combination generator), or to filter (and combine) the contents of a single one (see Filter generators). The sequence of their output, during a certain number of clock cycles, then produces the pseudorandom sequence which is used in a Vernam cipher (that is, which is bitwisely added to the plaintext to produce the ciphertext). In block ciphers (see Block cipher, Data Encryption Standard (DES), Advanced Encryption Standard (Rijndael/AES)), the S-boxes are designed by appropriate composition of nonlinear Boolean functions.
An n-variable Boolean function f is a function from the set \(F_2^n\) of all binary vectors \(x=(x_1,\dots,x_n)\) of length n to the field \(F_2=\{0,1\}\). The number nof variables is rarely large in practice. In the case of...
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Carlet, C. (2005). Boolean Functions. In: van Tilborg, H.C.A. (eds) Encyclopedia of Cryptography and Security. Springer, Boston, MA . https://doi.org/10.1007/0-387-23483-7_40
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