I just goggle'd the constants and it looks like a regular 8-round TEA to me.
The official source has 0x9E3779B9 as the delta (which is -Y_STEP),
"y+= step;" and "y -= step;" switch places to match;
Y_INIT is then just (8 * DELTA)&0xFFFFFFFF.

Where is this code from?
I presume reverse engineering of the BL files (surely explains negating the
constant).
If so, why can't we RE (or just take the keys off) other header versions?

R.

-----Original Message-----
From: rockbox-dev-bounces@cool.haxx.se
[mailto:rockbox-dev-bounces@cool.haxx.se] On Behalf Of Daniel Stenberg
Sent: Friday, June 30, 2006 8:41 PM
To: Rockbox Development
Subject: mi4, BL and more

Hello

I just wanted to put your attention to the fact that we now have a first
(en/de)crypt tool for (some) mi4 files. All details on my mi4 page:

         http://daniel.haxx.se/sansa/mi4.html

We can use some help to get the rest figured out as well!

--
  Daniel Stenberg -- http://www.rockbox.org/ -- http://daniel.haxx.se/