Crypto on Insignificant Bits

sae.py

Thu, 31 Dec 2015 23:57:47 +0000

For a while now, I’ve wanted an easy way to decrypt a mesh packet capture when I know the SAE passphrase. This would be quite handy for debugging.

I reasoned that, if I knew the shared secret, and had captured the over-the-air exchange, it should be possible to make such a tool, right? We know everything each station knows in that case, don’t we?

So I spent a bit of time last week reimplementing SAE in python to come to grips with its various steps. And I found my reasoning was flawed.

Now (mostly) encrypted

Wed, 18 Nov 2015 01:52:51 +0000

I signed up for the let’s encrypt beta and got my cert setup today. I let my old CA-purchased cert lapse when it came for re-up a couple of years ago, so happy there’s soon to be a free alternative.

Enjoy the HTTPS! (Except for some stray mixed content I need to kill – sorry for that.)

Footprint, Part 2

Mon, 12 Aug 2013 14:28:18 +0000

My recent posting of ASCII art was intentionally subtle, perhaps overly so. If you haven’t figured it out by now, it is a C program that announces the birth of our second child. When compiled and executed, it prints:

Ian Yit-Sing Copeland Born 5 August, 2013 at 02:49 Weight 6 lbs 11 oz

In this post, I will explain how I created it.

Like many a C practitioner, I’ve always found International Obfuscated C Code Contest entries to be at once entertaining and mystifying. While I don’t consider this effort to be near the level of IOCCC entries, I thought it might be fun to try my own IOCCC-lite ASCII art program.

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.

New GPG key

Tue, 11 Oct 2011 17:34:59 +0000

My previous key isn’t yet two years old, but given the recent kernel.org reboot, I created a new keypair today. The fingerprint is:

11FB F4D3 92A6 F32B CB4E  2E07 8411 1007 23B2 B915

The old key will be valid for a little while longer. As for korg, perhaps it’s time I used github anyway. My OMFS tree is over there now, lonely and waiting for me to feed him some patches.