<s>
BackupHDDVD	B-General_Concept
is	O
a	O
small	O
computer	B-Application
software	I-Application
utility	B-Application
program	I-Application
available	O
in	O
command	B-Application
line	I-Application
and	O
GUI	B-Application
versions	O
which	O
aids	O
in	O
the	O
decryption	O
of	O
commercial	O
HD	B-Operating_System
DVD	I-Operating_System
discs	O
protected	O
by	O
the	O
Advanced	O
Access	O
Content	O
System	O
.	O
</s>
<s>
It	O
is	O
used	O
to	O
back	B-Protocol
up	I-Protocol
discs	O
,	O
often	O
to	O
enable	O
playback	O
on	O
hardware	O
configurations	O
without	O
full	O
support	O
for	O
HDCP	B-Protocol
.	O
</s>
<s>
Written	O
by	O
an	O
anonymous	O
programmer	O
using	O
the	O
handle	O
Muslix64	B-General_Concept
,	O
BackupHDDVD	B-General_Concept
is	O
distributed	O
with	O
none	O
of	O
the	O
cryptographic	O
keys	O
necessary	O
for	O
decryption	O
.	O
</s>
<s>
Users	O
wanting	O
to	O
use	O
the	B-Application
software	I-Application
to	O
decrypt	O
a	O
protected	O
disc	O
's	O
contents	O
must	O
obtain	O
the	O
appropriate	O
keys	O
separately	O
,	O
a	O
task	O
with	O
which	O
neither	O
the	O
original	O
author	O
nor	O
his	O
or	O
her	O
versions	O
of	O
BackupHDDVD	B-General_Concept
assist	O
.	O
</s>
<s>
BackupHDDVD	B-General_Concept
represented	O
the	O
first	O
known	O
successful	O
attack	O
against	O
AACS	O
.	O
</s>
<s>
The	O
utility	O
circumvents	O
content	O
protection	O
by	O
decrypting	O
video	O
files	O
directly	O
with	O
AES	B-Algorithm
,	O
the	O
underling	O
cryptographic	O
cipher	O
used	O
by	O
AACS	O
.	O
</s>
<s>
Using	O
this	O
technique	O
,	O
BackupHDDVD	B-General_Concept
is	O
able	O
to	O
completely	O
bypass	O
the	O
AACS	O
chain	O
of	O
trust	O
,	O
rendering	O
it	O
immune	O
to	O
revocation	O
.	O
</s>
<s>
The	O
cost	O
of	O
this	O
immunity	O
is	O
that	O
users	O
are	O
forced	O
to	O
rely	O
on	O
keys	O
leaking	O
from	O
commercial	O
player	O
software	O
to	O
use	O
BackupHDDVD	B-General_Concept
with	O
new	O
discs	O
.	O
</s>
<s>
According	O
to	O
the	O
creator	O
of	O
BackupHDDVD	B-General_Concept
,	O
he	O
or	O
she	O
first	O
set	O
out	O
to	O
circumvent	O
AACS	O
to	O
bypass	O
a	O
restriction	O
in	O
software	O
HD	B-Operating_System
DVD	I-Operating_System
players	O
which	O
reduced	O
the	O
quality	O
of	O
AACS	O
restricted	O
1080p	O
high	O
definition	O
video	O
to	O
that	O
of	O
standard	O
definition	O
DVD	O
video	O
or	O
refused	O
to	O
play	O
outright	O
unless	O
an	O
HDCP	B-Protocol
compliant	O
chain	O
of	O
video	O
hardware	O
was	O
present	O
.	O
</s>
<s>
At	O
the	O
time	O
only	O
a	O
few	O
computer	B-Device
monitors	I-Device
and	O
video	B-Device
cards	I-Device
supported	O
HDCP	B-Protocol
.	O
</s>
<s>
As	O
a	O
result	O
,	O
configurations	O
that	O
would	O
have	O
allowed	O
high-definition	O
HD	B-Operating_System
DVD	I-Operating_System
viewing	O
in	O
software	O
players	O
were	O
exceptionally	O
rare	O
.	O
</s>
<s>
On	O
December	O
18	O
,	O
2006	O
,	O
a	O
video	O
which	O
showed	O
BackupHDDVD	B-General_Concept
being	O
used	O
to	O
decrypt	O
and	O
copy	O
the	O
film	O
Full	O
Metal	O
Jacket	O
to	O
a	O
hard	O
drive	O
was	O
uploaded	O
to	O
YouTube	B-General_Concept
.	I-General_Concept
</s>
<s>
A	O
link	O
to	O
the	O
file	O
was	O
then	O
posted	O
by	O
the	O
utility	O
's	O
creator	O
on	O
the	O
forums	O
of	O
Doom9	O
,	O
a	O
website	O
devoted	O
to	O
DVD	O
backup	B-Protocol
.	O
</s>
<s>
The	O
author	O
elaborated	O
in	O
another	O
forum	O
post	O
,	O
claiming	O
that	O
keys	O
could	O
be	O
obtained	O
by	O
exploiting	O
the	O
necessity	O
for	O
them	O
to	O
be	O
held	O
in	O
memory	B-Architecture
to	O
allow	O
playback	O
in	O
player	O
software	B-Application
.	I-Application
</s>
<s>
On	O
January	O
2	O
,	O
2007	O
,	O
the	O
author	O
posted	O
the	O
1.0	O
version	O
of	O
the	O
BackupHDDVD	B-General_Concept
utility	O
,	O
which	O
included	O
support	O
for	O
the	O
decoding	O
of	O
discs	O
using	O
volume	O
keys	O
.	O
</s>
<s>
Further	O
development	O
of	O
BackupHDDVD	B-General_Concept
was	O
being	O
hosted	O
on	O
SourceForge	B-Application
until	O
the	O
site	O
received	O
a	O
DMCA	O
takedown	O
notice	O
alleging	O
a	O
violation	O
in	O
late	O
February	O
.	O
</s>
<s>
Several	O
versions	O
of	O
BackupHDDVD	B-General_Concept
have	O
been	O
released	O
by	O
individuals	O
other	O
than	O
the	O
original	O
author	O
,	O
including	O
some	O
versions	O
with	O
GUIs	B-Application
and	O
the	O
ability	O
to	O
locate	O
keys	O
on	O
the	O
internet	O
or	O
scan	O
for	O
them	O
in	O
memory	B-Architecture
automatically	O
.	O
</s>
<s>
HDDecrypter	O
,	O
a	O
port	O
of	O
BackupHDDVD	B-General_Concept
to	O
C	B-Language
with	O
a	O
native	O
Windows	B-Application
GUI	B-Application
is	O
also	O
available	O
.	O
</s>
<s>
While	O
development	O
of	O
BackupHDDVD	B-General_Concept
has	O
ceased	O
,	O
a	O
commercial	O
HD	B-Operating_System
DVD	I-Operating_System
decryption	O
utility	O
called	O
Slysoft	O
AnyDVD	O
HD	O
exists	O
which	O
relies	O
on	O
compromised	O
AACS	O
processing	O
or	O
media	O
keys	O
to	O
allow	O
for	O
the	O
backup	B-Protocol
or	O
unrestricted	O
viewing	O
of	O
any	O
AACS-protected	O
discs	O
without	O
the	O
need	O
for	O
title	O
or	O
volume	O
keys	O
.	O
</s>
<s>
If	O
a	O
device	O
key	O
is	O
to	O
be	O
revoked	B-Protocol
,	O
the	O
media	O
key	O
blocks	O
on	O
all	O
discs	O
manufactured	O
after	O
the	O
time	O
of	O
revocation	O
are	O
encrypted	O
in	O
a	O
way	O
which	O
does	O
not	O
enable	O
the	O
revoked	B-Protocol
device	O
to	O
obtain	O
a	O
valid	O
processing	O
key	O
.	O
</s>
<s>
Users	O
trying	O
to	O
view	O
new	O
content	O
on	O
a	O
revoked	B-Protocol
player	O
would	O
be	O
forced	O
to	O
upgrade	O
their	O
player	O
software	O
to	O
a	O
more	O
secure	O
version	O
,	O
thereby	O
limiting	O
the	O
scope	O
of	O
the	O
compromise	O
each	O
time	O
an	O
exploit	O
is	O
discovered	O
.	O
</s>
<s>
While	O
a	O
compromised	O
device	O
or	O
processing	O
key	O
could	O
be	O
used	O
to	O
decrypt	O
a	O
large	O
number	O
of	O
discs	O
,	O
BackupHDDVD	B-General_Concept
does	O
not	O
use	O
these	O
keys	O
because	O
they	O
can	O
be	O
revoked	B-Protocol
by	O
AACS	O
LA	O
.	O
</s>
<s>
Because	O
the	O
AACS	O
revocation	O
system	O
works	O
by	O
preventing	O
a	O
given	O
device	O
or	O
player	O
from	O
calculating	O
a	O
valid	O
volume	O
unique	O
key	O
,	O
BackupHDDVD	B-General_Concept
circumvents	O
the	O
system	O
entirely	O
by	O
relying	O
on	O
volume	O
or	O
title	O
keys	O
leaked	O
from	O
authorized	O
players	O
.	O
</s>
<s>
With	O
these	O
keys	O
BackupHDDVD	B-General_Concept
is	O
not	O
subject	O
to	O
device	O
revocation	O
and	O
is	O
able	O
to	O
decrypt	O
the	O
content	O
directly	O
,	O
bypassing	O
the	O
key	O
exchange	O
and	O
verification	O
process	O
.	O
</s>
<s>
Users	O
must	O
have	O
either	O
found	O
decryption	O
keys	O
themselves	O
or	O
obtained	O
them	O
elsewhere	O
for	O
most	O
versions	O
of	O
BackupHDDVD	B-General_Concept
to	O
work	O
.	O
</s>
<s>
Through	O
a	O
standard	O
AES	B-Algorithm
library	B-Library
,	O
it	O
then	O
decrypts	O
each	O
video	O
file	O
on	O
the	O
disc	O
using	O
the	O
appropriate	O
keys	O
and	O
writes	O
the	O
results	O
to	O
a	O
location	O
specified	O
by	O
the	O
user	O
.	O
</s>
<s>
Originally	O
intended	O
to	O
be	O
a	O
proof	O
of	O
concept	O
,	O
BackupHDDVD	B-General_Concept
is	O
severely	O
limited	O
in	O
its	O
ability	O
to	O
produce	O
fully	O
functional	O
copies	O
of	O
commercial	O
discs	O
.	O
</s>
<s>
The	O
utility	O
cannot	O
process	O
HD	B-Operating_System
DVD	I-Operating_System
navigation	O
functionality	O
which	O
enables	O
menus	O
,	O
chapters	O
,	O
secondary	O
audio	O
tracks	O
and	O
subtitles	O
,	O
so	O
these	O
features	O
are	O
inaccessible	O
in	O
copies	O
created	O
by	O
BackupHDDVD	B-General_Concept
.	O
</s>
<s>
Under	O
United	O
States	O
anti-circumvention	O
law	O
created	O
by	O
the	O
Digital	O
Millennium	O
Copyright	O
Act	O
,	O
BackupHDDVD	B-General_Concept
may	O
qualify	O
as	O
a	O
device	O
primarily	O
intended	O
to	O
"	O
circumvent	O
a	O
technological	O
measure	O
that	O
effectively	O
controls	O
access	O
to	O
a	O
 [ protected ] 	O
work.	O
"	O
</s>
<s>
One	O
article	O
compared	O
proponents	O
of	O
BackupHDDVD	B-General_Concept
to	O
terrorists	O
.	O
</s>
<s>
In	O
fact	O
no	O
cryptographic	O
weaknesses	O
constituting	O
a	O
crack	O
have	O
yet	O
been	O
found	O
in	O
AES	B-Algorithm
,	O
the	O
underlying	O
cryptographic	O
system	O
of	O
AACS	O
.	O
</s>
<s>
Initially	O
,	O
it	O
was	O
thought	O
that	O
the	O
compromise	O
of	O
HD	B-Operating_System
DVD	I-Operating_System
's	O
security	O
would	O
entice	O
some	O
studios	O
into	O
adopting	O
the	O
competing	O
Blu-ray	O
format	O
,	O
but	O
Blu-ray	O
'	O
s	O
AACS	O
implementation	O
has	O
since	O
been	O
circumvented	O
using	O
a	O
similar	O
method	O
.	O
</s>
<s>
There	O
was	O
some	O
speculation	O
that	O
the	O
player	O
used	O
by	O
the	O
utility	O
's	O
author	O
to	O
obtain	O
keys	O
would	O
be	O
revoked	B-Protocol
.	O
</s>
<s>
Both	O
companies	O
have	O
since	O
released	O
updates	O
for	O
their	O
player	O
software	B-Application
.	I-Application
</s>
<s>
The	O
consortium	O
behind	O
the	O
HD	B-Operating_System
DVD	I-Operating_System
format	O
and	O
the	O
studios	O
delivering	O
films	O
on	O
the	O
format	O
did	O
not	O
release	O
an	O
official	O
statement	O
beyond	O
that	O
they	O
were	O
investigating	O
the	O
utility	O
.	O
</s>
<s>
On	O
January	O
24	O
,	O
2007	O
AACS	O
LA	O
issued	O
a	O
statement	O
acknowledging	O
that	O
AACS	O
security	O
had	O
been	O
compromised	O
while	O
urging	O
software	O
vendors	O
to	O
limit	O
the	O
availability	O
of	O
keys	O
in	O
memory	B-Architecture
.	O
</s>
<s>
Beginning	O
with	O
discs	O
manufactured	O
in	O
late	O
April	O
,	O
versions	O
of	O
PowerDVD	O
and	O
WinDVD	O
responsible	O
for	O
leaking	O
keys	O
have	O
been	O
revoked	B-Protocol
and	O
free	O
updates	O
are	O
available	O
to	O
owners	O
of	O
affected	O
versions	O
.	O
</s>
