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In cryptography, an S-box (substitution-box) is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext, thus ensuring Shannon's property of confusion. Mathematically, an S-box is a nonlinear [1] vectorial Boolean function ...
The Rijndael S-box can be replaced in the Rijndael cipher, [1] which defeats the suspicion of a backdoor built into the cipher that exploits a static S-box. The authors claim that the Rijndael cipher structure is likely to provide enough resistance against differential and linear cryptanalysis even if an S-box with "average" correlation ...
This substitution should be one-to-one, to ensure invertibility (hence decryption). In particular, the length of the output should be the same as the length of the input (the picture on the right has S-boxes with 4 input and 4 output bits), which is different from S-boxes in general that could also change the length, as in Data Encryption ...
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.
Table compares implementations of block ciphers. Block ciphers are defined as being deterministic and operating on a set number of bits (termed a block) using a symmetric key. Each block cipher can be broken up into the possible key sizes and block cipher modes it can be run with.
Confusion in a symmetric cipher is obscuring the local correlation between the input , and output by varying the application of the key to the data, while diffusion is hiding the plaintext statistics by spreading it over a larger area of ciphertext. [2] Although ciphers can be confusion-only (substitution cipher, one-time pad) or diffusion-only ...
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.
Product ciphers use alternating substitution and transposition phases to achieve both confusion and diffusion respectively. There are two more slightly confusing things in the present text, I will change them, too: I think it is dangerous to connect the word "substitution" in a substitution–permutation network with a substitution cipher.