[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Bug-xorriso] driver and disc ID acquiring, hidden track

From: Thomas Schmitt
Subject: Re: [Bug-xorriso] driver and disc ID acquiring, hidden track
Date: Wed, 28 Oct 2015 10:59:14 +0100


> But before making use of the Serial Number of the drives and the media

Be aware that i failed to find a Medium with Id among
my collection of recordables.
Further one of my drives went mad when i forced the inquiry
despite the flag that says "No Medium Id available".

> I must find one method to write some invisible, inaccessible or unduplicated
> content into the disc.

I don't know any. And if i knew, my role in this project would
force me to tell everybody or nobody. Neither would serve your

What you need would be burner hardware which writes to places
on the disc where no other burner will write. But this must still
be readable by normal drives, i understand.

The video industry had the same problem and found no better
solution than their shaky cryptographic stuff: CSS, AACS.
They do have special hardware for writing, but the demand to
have their stuff readable by general purpose computers keeps
them from using special hardware features.

> Google Patents,

As a GNU maintainer i first have to shout "Boooo !" now.

You will need permission to use them.

> 1. Writing some contents into the region on the disc that can not be written
> under normal conditions, so the content in this region can not be written
> into the copied media;

Such tricks were possible with CD and special hardware which in
part was available publicly.
But the problem of reading such special physical patterns and
properly interpreting them as logical patterns caused trouble
back then.
Reader drives of DVD and BD have clear ideas about physical-to-logical
transition. What they don't know, they don't read.

> 2. Insert flags that cannot be duplicated directly, so the copied
> media will not include these flags;

I assume they mean bits in the first logical level of representation.
At this level the data blocks are inflated and scrambled for best
random distribution of error impact, augmented by checksums for
error detection and correction, and controlled by management bits.

Those management bits may have unused or forbidden combinations
which one could use to place a message or a trap. One may also
alter the meaning of the checksums. E.g. by a secret salt for
each block's data.

For CD and DVD there are ECMA specs in the internet for free.
After the electrical engineering stuff, they have descriptions
of logical aspects: data formats, checksums, management info.
  ECMA-130 for CD-ROM, logics starts at section 14.
  ECMA-267 for DVD-ROM, logics starts at section 4.
This describes what readers may expect.

Afaik, the corresponding Blu-ray info is guarded by the
Blu-ray Disc Association. Last time i looked they wanted
3000 USD as yearly membership fee.

For the scope of my tasks those hardware specs are of few
interest anyways. I read SCSI specs SPC-3 and MMC-5, which
describe the common command set of all burners.
For CD there much sector entrails exposed to SCSI.
But DVD and BD at SCSI level just show logical blocks of
2048 payload bytes. No checksums, no management bits.

> Expecting your further guidance.

It seems that at best i can feed you with arguments for your
boss in order to explain that a new approach is needed to
the overall problem.
If the video industry did not find a convincing solution,
then you will hardly find one under the same general usage model.

Have a nice day :)


reply via email to

[Prev in Thread] Current Thread [Next in Thread]