AES Sbox and Pari/GP

Hello folks !

Lately I was interested in how to mathematically generate the AES substitution box. Actually, all the implementations of AES use a pre-filled table to compute the value of a substituted byte. The goal of this article is to understand how this table is computed.

In a first part, we will describe the mathematical transformation and in the second part we will see how to do the mathematical transformation of the Sbox with Pari-GP. Because of my crappy level in mathematics, this article can be mathematically wrong or incorrect, so if you have advices, you are welcome :).

The goal of the article is to understand how to find this table :

   | 0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
---|--|--|--|--|--|--|--|--|--|--|--|--|--|--|--|--|
00 |63 7c 77 7b f2 6b 6f c5 30 01 67 2b fe d7 ab 76 
10 |ca 82 c9 7d fa 59 47 f0 ad d4 a2 af 9c a4 72 c0 
20 |b7 fd 93 26 36 3f f7 cc 34 a5 e5 f1 71 d8 31 15 
30 |04 c7 23 c3 18 96 05 9a 07 12 80 e2 eb 27 b2 75 
40 |09 83 2c 1a 1b 6e 5a a0 52 3b d6 b3 29 e3 2f 84 
50 |53 d1 00 ed 20 fc b1 5b 6a cb be 39 4a 4c 58 cf 
60 |d0 ef aa fb 43 4d 33 85 45 f9 02 7f 50 3c 9f a8 
70 |51 a3 40 8f 92 9d 38 f5 bc b6 da 21 10 ff f3 d2 
80 |cd 0c 13 ec 5f 97 44 17 c4 a7 7e 3d 64 5d 19 73 
90 |60 81 4f dc 22 2a 90 88 46 ee b8 14 de 5e 0b db 
a0 |e0 32 3a 0a 49 06 24 5c c2 d3 ac 62 91 95 e4 79 
b0 |e7 c8 37 6d 8d d5 4e a9 6c 56 f4 ea 65 7a ae 08 
c0 |ba 78 25 2e 1c a6 b4 c6 e8 dd 74 1f 4b bd 8b 8a 
d0 |70 3e b5 66 48 03 f6 0e 61 35 57 b9 86 c1 1d 9e 
e0 |e1 f8 98 11 69 d9 8e 94 9b 1e 87 e9 ce 55 28 df 
f0 |8c a1 89 0d bf e6 42 68 41 99 2d 0f b0 54 bb 16 

NoSuchCon 2013 challenge - Write up and Methodology

I had to do a write-up for the NoSuchCon 2013 challenge to get my "usb missile launcher". I wanted to share this write-up to give some approaches to do the challenge. I’m really interested to have feedback, comments or ideas to improve the process.
In the first section of this paper, we will see the methodology to break the challenge, even the bad ideas. Then we will see how to automate the deobfuscation. In the third section, we will see how to attack the algorithm and we will end up with a small conclusion.

The link : https://github.com/kutio/nosuchcon2013-challenge/raw/master/doc/NoSuchCon2013-re-chall-writeup-v1.0.pdf

The sources : https://github.com/kutio/nosuchcon2013-challenge

Greetz: @0vercl0k who lost some neurones with me
             @elvanderb with his crazy challenge
             @skier who gave me some clever ideas

             @Taron__  who reviewed the write-up