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I don't understand how the AddRoundKey function works, because the following example is from the cipher authors. I`m trying to add 76 and 7d, and my result is f3. Could someone explain this?

8F 20 3E 06 5F C3 54 45 B5 FE B9 AC A7 A0 C6 76 +
86 2F 1F 65 3B 77 5B A1 D0 5C BC 2F 38 E2 D8 7D =
16 50 5E 6B 9B 3A B1 E6 86 5B 77 DC E0 82 A0 F4
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    $\begingroup$ well you got me curious, I was able to verify those numbers from the paper, and the fact that they should be combined using 64-bit addition since they are for an even round $\endgroup$
    – Richie Frame
    Jun 21, 2018 at 8:29
  • $\begingroup$ Every byte is off by one. From the least-significant (rightmost) byte leftwards, the even bytes are one too high and the odd bytes are one too low. It should be 15 4F 5D 6B 9B 3A AF E6 86 5B 75 DB E0 83 9E F3. $\endgroup$
    – forest ♦
    Mar 25, 2019 at 7:10

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