<s>
Protected	B-Protocol
Streaming	I-Protocol
is	O
a	O
DRM	O
technology	O
by	O
Adobe	O
.	O
</s>
<s>
Protected	B-Protocol
Streaming	I-Protocol
consists	O
of	O
many	O
different	O
techniques	O
;	O
basically	O
there	O
are	O
two	O
main	O
components	O
:	O
encryption	O
and	O
SWF	O
verification	O
.	O
</s>
<s>
This	O
technique	O
is	O
used	O
by	O
the	O
Hulu	B-Application
desktop	O
player	O
and	O
the	O
RTÉ	O
Player	O
.	O
</s>
<s>
Streamed	O
content	O
is	O
encrypted	O
by	O
the	O
Flash	B-Operating_System
Media	I-Operating_System
Server	I-Operating_System
"	O
on	O
the	O
fly	O
"	O
,	O
so	O
that	O
the	O
source	O
file	O
itself	O
does	O
not	O
need	O
to	O
be	O
encrypted	O
(	O
a	O
significant	O
difference	O
from	O
Microsoft	O
's	O
DRM	O
)	O
.	O
</s>
<s>
For	O
transmission	O
(	O
"	O
streaming	O
"	O
)	O
,	O
a	O
special	O
protocol	O
is	O
required	O
,	O
either	O
RTMPE	O
or	O
RTMPS	B-Operating_System
.	O
</s>
<s>
RTMPS	B-Operating_System
uses	O
SSL-encryption	O
.	O
</s>
<s>
In	O
contrast	O
,	O
RTMPE	O
is	O
designed	O
to	O
be	O
simpler	O
than	O
RTMPS	B-Operating_System
,	O
by	O
removing	O
the	O
need	O
to	O
acquire	O
a	O
SSL	B-Protocol
Certificate	O
.	O
</s>
<s>
RTMPE	O
makes	O
use	O
of	O
well-known	O
industry	O
standard	O
cryptographic	O
primitives	O
,	O
consisting	O
of	O
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
key	I-Protocol
exchange	I-Protocol
and	O
HMACSHA256	O
,	O
generating	O
a	O
pair	O
of	O
RC4	B-Algorithm
keys	O
,	O
one	O
of	O
which	O
is	O
then	O
used	O
to	O
encrypt	O
the	O
media	O
data	O
sent	O
by	O
the	O
server	O
(	O
the	O
audio	O
or	O
video	O
stream	O
)	O
,	O
while	O
the	O
other	O
key	O
is	O
used	O
to	O
encrypt	O
any	O
data	O
sent	O
to	O
the	O
server	O
.	O
</s>
<s>
RTMPE	O
caused	O
less	O
CPU-load	O
than	O
RTMPS	B-Operating_System
on	O
the	O
Flash	B-Operating_System
Media	I-Operating_System
Server	I-Operating_System
.	O
</s>
<s>
Tools	O
which	O
have	O
a	O
copy	O
of	O
the	O
well-known	O
constants	O
extracted	O
from	O
the	O
Adobe	B-Operating_System
Flash	I-Operating_System
Player	I-Operating_System
are	O
able	O
to	O
capture	O
RTMPE	O
streams	O
,	O
a	O
form	O
of	O
the	O
trusted	B-Protocol
client	I-Protocol
problem	O
.	O
</s>
<s>
Adobe	O
issued	O
DMCA	O
takedowns	O
on	O
RTMPE	O
recording	O
tools	O
,	O
including	O
rtmpdump	B-Operating_System
,	O
to	O
try	O
to	O
limit	O
their	O
distribution	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
rtmpdump	B-Operating_System
,	O
however	O
,	O
this	O
led	O
to	O
a	O
Streisand	O
effect	O
.	O
</s>
<s>
The	O
Adobe	B-Operating_System
Flash	I-Operating_System
Player	I-Operating_System
uses	O
a	O
well-known	O
constant	O
,	O
appended	O
to	O
information	O
derived	O
from	O
the	O
SWF	O
file	O
(	O
a	O
hash	O
of	O
the	O
file	O
and	O
its	O
size	O
)	O
,	O
as	O
input	O
to	O
HMACSHA256	O
.	O
</s>
<s>
The	O
Flash	B-Operating_System
Media	I-Operating_System
Server	I-Operating_System
uses	O
this	O
to	O
limit	O
access	O
to	O
those	O
clients	O
which	O
have	O
access	O
to	O
the	O
SWF	O
file	O
(	O
or	O
have	O
been	O
given	O
a	O
copy	O
of	O
the	O
hash	O
and	O
the	O
size	O
of	O
the	O
SWF	O
file	O
)	O
.	O
</s>
<s>
All	O
officially	O
allowed	O
clients	O
(	O
which	O
are	O
in	O
fact	O
*	O
.swf	O
files	O
)	O
need	O
to	O
be	O
placed	O
on	O
the	O
Flash	B-Operating_System
Media	I-Operating_System
Server	I-Operating_System
streaming	O
the	O
file	O
.	O
</s>
<s>
In	O
practice	O
,	O
therefore	O
,	O
Adobe	O
's	O
own	O
implementation	O
of	O
the	O
Macromedia	B-Operating_System
Flash	I-Operating_System
Player	I-Operating_System
is	O
the	O
only	O
client	O
which	O
does	O
not	O
allow	O
saving	O
to	O
a	O
local	O
file	O
.	O
</s>
<s>
The	O
only	O
possible	O
way	O
to	O
restrict	O
connections	O
to	O
a	O
Flash	B-Operating_System
Media	I-Operating_System
Server	I-Operating_System
is	O
to	O
use	O
a	O
list	O
of	O
known	O
hosts	O
,	O
to	O
avoid	O
the	O
whole	O
player	O
(	O
the	O
Flash	O
client	O
)	O
being	O
placed	O
on	O
an	O
unauthorised	O
website	O
.	O
</s>
