<s>
The	O
ISMA	O
Encryption	O
and	O
Authentication	O
,	O
Version	O
1.1	O
specification	O
(	O
or	O
ISMACryp	B-Algorithm
)	O
specifies	O
encryption	O
and	O
message	O
authentication	O
services	O
for	O
MPEG-4	B-Algorithm
over	O
RTP	B-Protocol
streams	O
.	O
</s>
<s>
ISMACryp	B-Algorithm
specification	O
defined	O
extensions	O
over	O
the	O
ISO	O
base	O
media	O
file	O
format	O
,	O
which	O
were	O
registered	O
by	O
the	O
registration	O
authority	O
for	O
code-points	O
in	O
"	O
MP4	O
Family	O
"	O
files	O
.	O
</s>
<s>
The	O
ISMACryp	B-Algorithm
2.0	O
specification	O
in	O
an	O
informative	O
"	O
Annex	O
F	O
"	O
provides	O
guidelines	O
on	O
how	O
ISMACryp	B-Algorithm
can	O
be	O
used	O
together	O
with	O
the	O
key	O
and	O
rights	O
management	O
system	O
of	O
OMA	O
DRM	O
v2	O
(	O
Open	O
Mobile	O
Alliance	O
DRM	O
)	O
.	O
</s>
<s>
The	O
Packetized	O
OMA	O
DRM	O
Content	O
Format	O
is	O
almost	O
based	O
on	O
ISMACryp	B-Algorithm
format	O
.	O
</s>
<s>
There	O
are	O
two	O
alternatives	O
to	O
ISMACryp	B-Algorithm
,	O
SRTP	B-Protocol
and	O
IPsec	B-Protocol
,	O
that	O
can	O
also	O
be	O
used	O
to	O
provide	O
service	O
and	O
content	O
protection	O
.	O
</s>
<s>
Whereas	O
ISMACryp	B-Algorithm
encrypts	O
MPEG-4	B-Algorithm
access	O
units	O
(	O
that	O
are	O
in	O
the	O
RTP	B-Protocol
payload	O
)	O
,	O
SRTP	B-Protocol
encrypts	O
the	O
whole	O
RTP	B-Protocol
payload	O
,	O
and	O
IPsec	B-Protocol
encrypts	O
packets	O
at	O
.	O
</s>
