How I nearly cracked it

Mon, 26 Dec 2011 20:39:33 +0000

Here’s my methodology for part 1 of the Can You Crack It puzzle.

(Spoilers below)

eb 04 af c2 bf a3 81 ec  00 01 00 00 31 c9 88 0c
0c fe c1 75 f9 31 c0 ba  ef be ad de 02 04 0c 00
d0 c1 ca 08 8a 1c 0c 8a  3c 04 88 1c 04 88 3c 0c
fe c1 75 e8 e9 5c 00 00  00 89 e3 81 c3 04 00 00
00 5c 58 3d 41 41 41 41  75 43 58 3d 42 42 42 42
75 3b 5a 89 d1 89 e6 89  df 29 cf f3 a4 89 de 89
d1 89 df 29 cf 31 c0 31  db 31 d2 fe c0 02 1c 06
8a 14 06 8a 34 1e 88 34  06 88 14 1e 00 f2 30 f6
8a 1c 16 8a 17 30 da 88  17 47 49 75 de 31 db 89
d8 fe c0 cd 80 90 90 e8  9d ff ff ff 41 41 41 41

Anyone who has stared long and hard at x86 hexdumps before will immediately think “I know this, this is an intel system!” The value 0xdeadbeef in little-endian format is a dead-giveaway, as are the 0x90 (NOP) instructions. I know a couple of ways to go from a block of machine code to the corresponding code. One way, like scripts/decodecode in the kernel, is to make a .S file with .byte directives, assemble it, and run objdump over the object file.

I can nearly crack it

Wed, 07 Dec 2011 21:29:37 +0000

The GCHQ (that’s British for NSA) has been running a marketing gimmick to find new people to read your tweets. On this website, you will find an enigmatic hexdump, and a prompt for a keyword. Supposedly if you get it correct, then you get forwarded to their job site. I don’t care about the job aspect, but I do enjoy a good puzzle.

I’ll add my details and methodology in a follow-up post after the clock runs out, so as not to spoil anything for casual readers who want to take their own look. There are a few good clues in the hexdump if you have previously spent any time looking at real ones.

X86 on Insignificant Bits

How I nearly cracked it

I can nearly crack it