Problem 45213. AES-256 KeyExpansion()

David Hill

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Given a 32-byte hexadecimal character array representing the AES-256 input key, execute the AES-256 algorithm, KeyExpansion() and output the xth (input) key-word of this 60-word sequence as a 4x2 hexadecimal array. You will need the SubBytes() function done in one of my previous Cody problems.

Refer to this link: https://csrc.nist.gov/csrc/media/publications/fips/197/final/documents/fips-197.pdf

For example:

key='e32868331fa8ef0138de0de85478346aec5e3912b6029ae71691c384237a3eeb';
x=58;%want key-word number 58 out of 60
w=['d0';'eb';'7c';'8a'];%58th key-word

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Last Solution submitted on May 25, 2026

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