Yearly Archives: 2006

What Is DoubleTwist Ventures Up To?

I generally don’t like to talk about the top search terms that are driving traffic to this blog since doing so tends to have the effect of driving more traffic based on particular terms to the posts that discuss that particular term. But last month, I noticed that “doubletwist ventures” drove a huge amount of traffic to this old post.

Is it just me, or are DRM-cracking stories just not interesting anymore? Maybe I just think of cracked DRM to be a fait accompli— I accept it as a forgone conclusion that DRM can’t work and it’s just a matter of time before the specific DRM algorithms are recovered (that is, if it’s not just stock AES).

Omelettes!

At long last, I am getting around to posting some omelette pictures in an effort to re-hijack the search term. Not only is the site named for the breakfast food, it will have a post about the same illustrated with pictures. Omelettes– they’re not just about multimedia technology and reverse engineering anymore! Without further ado…


Omelette
This was an all-around well-done omelette.

Omelette cooking
This is an omelette in the early stages of cooking. I must have used most of the spices on my shelf for this one.

Omelette with jalapenos
This one looks like it has jalapenos baked in.

Omelette burned
Sometimes, things go bad. I probably just wasn’t watching this one and it burned. Looks like it is leaking chopped onions, too.

Not Letting It Go

I’m just going to keep guessing; it’s much easier than digging up actual, empirical data. I’m starting to come to grips with the idea that the number of valid sectors contained on a DVD disc is something that’s interpreted by the optical drive firmware and enforced by the same (as is the case for RPC-2 DVD region encoding). If that’s true, there is no point in using direct SCSI access to beg for sectors beyond the magic 6,992 limit on a standard Xbox disc. Ways around this? There’s the Xbox-Linux FTP trick alluded to in my cursory post on the matter…

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New Media Angle

After yesterday’s post I received a tip that I may wish to try getting at the Xbox disc data using the low-level Linux SCSI layer– the facility commonly known as SCSI generic, or simply ‘sg’. In order to make use of this facility, it is necessary to configure your Linux kernel with the right support (CONFIG_CHR_DEV_SG, CONFIG_BLK_DEV_IDESCSI, but not CONFIG_BLK_DEV_IDECD). Download and install the SCSI generic utilities from here (which do not compile on my AMD64 machine; fortunately, the x86-compiled utilities and associated shared library drop into the system perfectly). There are about 30 little sg* utilities in the package. One that caught my attention was sg_dd– your typical ‘dd’ Unix command, but for interacting with a SCSI device. I tested it out on a typical Xbox DVD:

$ sudo sg_dd if=/dev/sg0 of=dvd bs=2048 bpt=1 count=20
20+0 records in
20+0 records out

And, indeed, the beginning of the disc has the markings of a typical DVD filesystem. So let’s try to read beyond the 6,992-sector limit on a standard Xbox disc:

$ sudo sg_dd if=/dev/sg0 of=dvd bs=2048 bpt=1 count=2 skip=6991
reading: SCSI status: Check Condition
 Fixed format, current;  Sense key: Illegal Request
 Additional sense: Logical block address out of range

 Raw sense data (in hex):
        70 00 05 00 00 00 00 0a  00 00 00 00 21 00 00 00
        00 00
plus...: Driver_status=0x08 [DRIVER_SENSE, SUGGEST_OK]
sg_read failed, seek=1
Some error occurred,  remaining block count=1
1+0 records in
1+0 records out

I had to deal with all this SCSI nonsense in a previous life and I admit that this output is conjuring some sour memories. Anyway, it seems that the stock sg_dd command can not read beyond what the DVD header structure ostensibly reports as the size of the disc. There are a number of other utilities I need to investigate for potential. Failing that, it’s possible — with at least a modicum of effort — to program the sg layer. There may yet be a solution.

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