Advanced Encryption Standard: Difference between revisions

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AES is based on a design principle known as a [[substitution–permutation network]], and is efficient in both software and hardware.<ref>{{cite web |url=http://www.schneier.com/paper-twofish-final.pdf |title=The Twofish Team's Final Comments on AES Selection |display-authors=7 |author=Bruce Schneier |author2=John Kelsey |author3=Doug Whiting |author4=David Wagner |author5=Chris Hall |author6=Niels Ferguson |author7=Tadayoshi Kohno |author8=Mike Stay |date=May 2000 |url-status=live |archive-url=https://web.archive.org/web/20100102041117/http://schneier.com/paper-twofish-final.pdf |archive-date=2010-01-02}}</ref> Unlike its predecessor DES, AES does not use a [[Feistel network]]. AES is a variant of Rijndael, with a fixed [[block size (cryptography)|block size]] of 128 [[bit]]s, and a [[key size]] of 128, 192, or 256 bits. By contrast, Rijndael ''per se'' is specified with block and key sizes that may be any multiple of 32 bits, with a minimum of 128 and a maximum of 256 bits. Most AES calculations are done in a particular [[Finite field arithmetic|finite field]].

AES operates on a 4 × 4 [[rowcolumn-major order]] array of 16 bytes {{math|{{var|b}}{{sub|0}},{{thinsp}}{{var|b}}{{sub|1}},{{thinsp}}...,{{thinsp}}{{var|b}}{{sub|15}}}} termed the ''state'':<ref group="note">Large-block variants of Rijndael use an array with additional columns, but always four rows.</ref>

::<math>

\begin{bmatrix}