<s>
Card	B-Device
sharing	I-Device
,	O
also	O
known	O
as	O
control	O
word	O
sharing	O
,	O
is	O
a	O
method	O
of	O
allowing	O
multiple	O
clients	O
or	O
digital	O
television	O
receivers	O
to	O
access	O
a	O
subscription	O
television	O
network	O
with	O
only	O
one	O
valid	O
subscription	O
card	O
.	O
</s>
<s>
This	O
is	O
achieved	O
by	O
electronically	O
sharing	O
a	O
part	O
of	O
the	O
legitimate	O
conditional	B-Architecture
access	I-Architecture
smart	O
card	O
's	O
output	O
data	O
,	O
enabling	O
all	O
recipients	O
to	O
gain	O
simultaneous	O
access	O
to	O
scrambled	O
DVB	B-Application
streams	O
,	O
held	O
on	O
the	O
encrypted	O
television	O
network	O
.	O
</s>
<s>
The	O
theory	O
of	O
card	B-Device
sharing	I-Device
as	O
a	O
potential	O
attack	O
vector	O
on	O
pay	O
TV	O
encryption	O
was	O
provided	O
in	O
the	O
book	O
European	O
Scrambling	O
Systems	O
by	O
John	O
McCormac	O
in	O
1996	O
;	O
leading	O
to	O
the	O
term	O
"	O
McCormac	O
Hack	O
"	O
to	O
be	O
used	O
to	O
describe	O
early	O
card-sharing	O
systems	O
.	O
</s>
<s>
The	O
security	O
of	O
conditional	B-Architecture
access	I-Architecture
smart	O
card	O
technology	O
is	O
limited	O
by	O
the	O
security	O
of	O
the	O
DVB	B-Application
standard	O
in	O
which	O
it	O
operates	O
.	O
</s>
<s>
The	O
standard	O
practice	O
of	O
a	O
legitimate	O
smart	O
card	O
is	O
to	O
decrypt	O
an	O
ECM	O
(	O
Entitlement	B-Architecture
Control	I-Architecture
Message	I-Architecture
)	O
,	O
which	O
then	O
provides	O
the	O
control	O
word	O
,	O
which	O
allows	O
the	O
viewing	O
of	O
scrambled	O
material	O
.	O
</s>
<s>
With	O
card	B-Device
sharing	I-Device
,	O
however	O
,	O
the	O
smart	O
card	O
and	O
its	O
security	O
features	O
are	O
bypassed	O
;	O
software	O
intercepts	O
the	O
decrypted	O
control	O
word	O
and	O
allows	O
the	O
user	O
to	O
share	O
it	O
across	O
a	O
computer	O
network	O
.	O
</s>
<s>
Card	B-Device
sharing	I-Device
has	O
established	O
itself	O
as	O
popular	O
method	O
of	O
pirate	B-Application
decryption	I-Application
.	O
</s>
<s>
Much	O
of	O
the	O
development	O
of	O
card	B-Device
sharing	I-Device
hardware	O
and	O
software	O
has	O
taken	O
place	O
in	O
Europe	O
,	O
where	O
national	O
boundaries	O
mean	O
that	O
home	O
users	O
are	O
able	O
to	O
receive	O
satellite	O
television	O
signals	O
from	O
many	O
countries	O
but	O
are	O
unable	O
to	O
legally	O
subscribe	O
to	O
them	O
due	O
to	O
licensing	O
restrictions	O
on	O
broadcasters	O
.	O
</s>
<s>
Other	O
networks	O
have	O
also	O
been	O
created	O
,	O
whereby	O
one	O
server	B-Application
has	O
multiple	O
legitimate	O
subscription	O
cards	O
connected	O
to	O
it	O
.	O
</s>
<s>
Access	O
to	O
this	O
server	B-Application
is	O
then	O
restricted	O
to	O
those	O
who	O
pay	O
the	O
server	B-Application
's	O
owner	O
their	O
own	O
subscription	O
fee	O
.	O
</s>
<s>
An	O
arguably	O
legitimate	O
use	O
for	O
card	B-Device
sharing	I-Device
is	O
the	O
sharing	O
of	O
the	O
control	O
word	O
within	O
a	O
home	O
network	O
,	O
where	O
the	O
subscriber	O
is	O
authorised	O
by	O
the	O
subscription	O
television	O
network	O
to	O
decrypt	O
their	O
signal	O
,	O
using	O
one	O
smart	O
card	O
.	O
</s>
<s>
However	O
,	O
in	O
some	O
cases	O
the	O
contract	O
between	O
the	O
subscriber	O
and	O
the	O
content	O
provider	O
implicitly	O
or	O
explicitly	O
prohibits	O
this	O
kind	O
of	O
card	B-Device
sharing	I-Device
.	O
</s>
<s>
Card	B-Device
sharing	I-Device
is	O
a	O
particular	O
concern	O
to	O
conditional	B-Architecture
access	I-Architecture
providers	O
,	O
and	O
their	O
respective	O
pay-TV	O
companies	O
,	O
as	O
well	O
as	O
the	O
DVB	B-Application
consortium	O
.	O
</s>
<s>
Card	B-Device
sharing	I-Device
utilises	O
the	O
integral	O
scrambling	O
system	O
of	O
the	O
DVB	B-Application
standard	O
,	O
DVB-CSA	B-Device
,	O
meaning	O
that	O
every	O
provider	O
of	O
scrambled	O
DVB	B-Application
content	O
has	O
potential	O
to	O
be	O
affected	O
by	O
it	O
.	O
</s>
<s>
One	O
technical	O
method	O
,	O
implemented	O
by	O
providers	O
such	O
as	O
Irdeto	O
and	O
NDS	B-Device
,	O
is	O
to	O
update	O
the	O
software	O
of	O
digital	O
receivers	O
provided	O
by	O
the	O
subscription	O
television	O
service	O
.	O
</s>
<s>
Rather	O
than	O
sending	O
a	O
plain	O
text	O
control	O
word	O
from	O
the	O
smart	O
card	O
to	O
the	O
receiver	O
's	O
microprocessor	O
,	O
which	O
can	O
be	O
intercepted	O
,	O
the	O
decrypted	O
ECM	O
will	O
in	O
fact	O
be	O
an	O
encrypted	O
control	O
word	O
,	O
which	O
can	O
only	O
be	O
decrypted	O
by	O
a	O
legitimate	O
,	O
non	O
card	B-Device
sharing	I-Device
capable	O
,	O
receiver	O
.	O
</s>
<s>
With	O
changes	O
occurring	O
as	O
frequently	O
as	O
once	O
every	O
few	O
seconds	O
,	O
extra	O
stress	O
is	O
put	O
onto	O
the	O
smart	O
card	B-Device
sharing	I-Device
system	O
,	O
meaning	O
that	O
clients	O
may	O
be	O
frustrated	O
by	O
short	O
,	O
frequent	O
,	O
missed	O
viewing	O
periods	O
.	O
</s>
<s>
One	O
significant	O
problem	O
for	O
internet	O
card	B-Device
sharing	I-Device
is	O
that	O
the	O
activity	O
can	O
be	O
traced	O
,	O
through	O
tracing	O
of	O
the	O
originating	O
IP	B-Protocol
address	I-Protocol
-	O
though	O
this	O
does	O
not	O
identify	O
an	O
individual	O
it	O
can	O
lead	O
to	O
a	O
specific	O
ISP	O
and/or	O
TV	O
service	O
subscription	O
.	O
</s>
<s>
Cases	O
of	O
criminal	O
charges	O
have	O
been	O
brought	O
against	O
card	B-Device
sharing	I-Device
hosts	O
.	O
</s>
<s>
In	O
August	O
2009	O
,	O
a	O
Liverpool	B-Application
man	O
was	O
prosecuted	O
for	O
re-selling	O
the	O
services	O
of	O
a	O
card	B-Device
sharing	I-Device
network	O
to	O
paying	O
customers	O
.	O
</s>
<s>
In	O
2007	O
,	O
the	O
DVB	B-Application
Project	I-Application
approved	O
and	O
began	O
licensing	O
a	O
new	O
scrambling	O
system	O
,	O
CSA3	O
,	O
for	O
protecting	O
DVB	B-Application
content	O
.	O
</s>
<s>
This	O
new	O
system	O
,	O
upon	O
implementation	O
,	O
will	O
attempt	O
to	O
eradicate	O
many	O
of	O
the	O
flaws	O
with	O
the	O
original	O
DVB-CSA	B-Device
system	O
,	O
including	O
introducing	O
an	O
AES	O
based	O
128-bit	O
key	O
system	O
.	O
</s>
<s>
The	O
system	O
will	O
reportedly	O
be	O
"	O
hardware	O
friendly	O
and	O
software	O
unfriendly	O
"	O
,	O
indicating	O
that	O
reverse	O
engineering	O
of	O
the	O
system	O
,	O
required	O
for	O
the	O
creation	O
of	O
card	B-Device
sharing	I-Device
applications	O
,	O
will	O
be	O
very	O
difficult	O
.	O
</s>
