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# Hmk4-Sol - CIS 3362 Homework 4 Solution Advanced Encryption...

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CIS 3362 : Homework # 4 Solution Advanced Encryption Standard 1) Show the first eight words (w[4] through w[11]) of the key expansion for a 128-bit key of all ones. Calculating w[4] : Here, i = 4 temp = w[i-1] = w[3] = ffffffff RotWord(temp) = ffffffff SubWord(RotWord(temp)) = 16161616 (using the S-box table) Rcon[4/4] = 01000000 (using round constant table) XORing SubWord with Rcon[4/4] : temp= 16161616 XOR 01000000 = 17161616 XORing w[4-4] with temp we get w[4] , hence w[4] = w[0] XOR temp = ffffffff XOR 17161616 = e8e9e9e9 The next three keys are just calculated using XORS with ffffffff. These are: w[5] = 17 16 16 16 w[6] = e8 e9 e9 e9 w[7] = 17 16 16 16 Calculating w[8] : Here, i = 8 temp = w[i-1] = w[7] = 17161616 RotWord(temp) = 16161617

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SubWord(RotWord(temp)) = 474747f0 (using the S-box table) Rcon[8/4] = 02000000 (using round constant table) XORing SubWord with Rcon[8/4] : temp= 474747f0 XOR 02000000 = 454747f0 XORing w[8-4] with temp we get w[8] , hence w[8] = w[4] XOR temp = e8e9e9e9 XOR 454747f0 =
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Hmk4-Sol - CIS 3362 Homework 4 Solution Advanced Encryption...

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