<s>
Multimedia	O
Internet	O
KEYing	O
(	O
MIKEY	B-Protocol
)	O
is	O
a	O
key	O
management	O
protocol	O
that	O
is	O
intended	O
for	O
use	O
with	O
real-time	O
applications	O
.	O
</s>
<s>
It	O
can	O
specifically	O
be	O
used	O
to	O
set	O
up	O
encryption	O
keys	O
for	O
multimedia	O
sessions	O
that	O
are	O
secured	O
using	O
SRTP	B-Protocol
,	O
the	O
security	O
protocol	O
commonly	O
used	O
for	O
securing	O
real-time	O
communications	O
such	O
as	O
VoIP	O
.	O
</s>
<s>
MIKEY	B-Protocol
was	O
first	O
defined	O
in	O
RFC	O
3830	O
.	O
</s>
<s>
Additional	O
MIKEY	B-Protocol
modes	O
have	O
been	O
defined	O
in	O
RFC	O
4650	O
,	O
RFC	O
4738	O
,	O
RFC	O
6043	O
,	O
RFC	O
6267	O
and	O
RFC	O
6509	O
.	O
</s>
<s>
As	O
described	O
in	O
RFC	O
3830	O
,	O
the	O
MIKEY	B-Protocol
protocol	O
is	O
intended	O
to	O
provide	O
end-to-end	O
security	O
between	O
users	O
to	O
support	O
a	O
communication	O
.	O
</s>
<s>
The	O
MIKEY	B-Protocol
protocol	O
may	O
also	O
authenticate	O
the	O
participants	O
of	O
the	O
communication	O
.	O
</s>
<s>
MIKEY	B-Protocol
provides	O
many	O
methods	O
to	O
share	O
the	O
session	O
key	O
and	O
authenticate	O
participants	O
.	O
</s>
<s>
MIKEY	B-Protocol
is	O
used	O
to	O
perform	O
key	O
management	O
for	O
securing	O
a	O
multimedia	O
communication	O
protocol	O
.	O
</s>
<s>
As	O
such	O
,	O
MIKEY	B-Protocol
exchanges	O
generally	O
occur	O
within	O
the	O
signalling	O
protocol	O
which	O
supports	O
the	O
communication	O
.	O
</s>
<s>
A	O
common	O
setup	O
is	O
for	O
MIKEY	B-Protocol
to	O
support	O
Secure	O
VoIP	O
by	O
providing	O
the	O
key	O
management	O
mechanism	O
for	O
the	O
VoIP	O
protocol	O
(	O
SRTP	B-Protocol
)	O
.	O
</s>
<s>
Key	O
management	O
is	O
performed	O
by	O
including	O
MIKEY	B-Protocol
messages	O
within	O
the	O
SDP	B-Language
content	O
of	O
SIP	B-Application
signalling	O
messages	O
.	O
</s>
<s>
MIKEY	B-Protocol
considers	O
how	O
to	O
secure	O
the	O
following	O
use	O
cases	O
:	O
</s>
<s>
Not	O
all	O
MIKEY	B-Protocol
methods	O
support	O
each	O
use	O
case	O
.	O
</s>
<s>
Each	O
MIKEY	B-Protocol
method	O
also	O
has	O
its	O
own	O
advantages	O
and	O
disadvantages	O
in	O
terms	O
of	O
feature	O
support	O
,	O
computational	O
complexity	O
and	O
latency	O
of	O
communication	O
setup	O
.	O
</s>
<s>
MIKEY	B-Protocol
supports	O
eight	O
different	O
methods	O
to	O
set	O
up	O
a	O
common	O
secret	O
(	O
to	O
be	O
used	O
as	O
e.g.	O
</s>
<s>
Pre-Shared	O
Key	O
(	O
MIKEY-PSK	O
)	O
:	O
This	O
is	O
the	O
most	O
efficient	O
way	O
to	O
handle	O
the	O
transport	O
of	O
the	O
Common	O
Secret	O
,	O
since	O
only	O
symmetric	B-Algorithm
encryption	I-Algorithm
is	O
used	O
and	O
only	O
a	O
small	O
amount	O
of	O
data	O
has	O
to	O
be	O
exchanged	O
.	O
</s>
<s>
Public-Key	B-Application
(	O
MIKEY-PK	O
)	O
:	O
The	O
Common	O
Secret	O
is	O
exchanged	O
with	O
the	O
help	O
of	O
public	B-Application
key	I-Application
encryption	I-Application
.	O
</s>
<s>
In	O
larger	O
systems	O
,	O
this	O
requires	O
a	O
PKI	B-Architecture
to	O
handle	O
the	O
secure	O
distribution	O
of	O
public	B-Application
keys	I-Application
.	O
</s>
<s>
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
(	O
MIKEY-DH	O
)	O
:	O
A	O
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
key	I-Protocol
exchange	I-Protocol
is	O
used	O
to	O
set	O
up	O
the	O
Common	O
Secret	O
.	O
</s>
<s>
Also	O
,	O
it	O
can	O
be	O
used	O
without	O
any	O
PKI	B-Architecture
.	O
</s>
<s>
DH-HMAC	O
(	O
MIKEY-DHHMAC	O
)	O
(	O
HMAC-Authenticated	O
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
)	O
:	O
This	O
is	O
a	O
light-weight	O
version	O
of	O
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
MIKEY	B-Protocol
:	O
instead	O
of	O
certificates	O
and	O
RSA	B-Architecture
signatures	O
it	O
uses	O
HMAC	B-Algorithm
to	O
authenticate	O
the	O
two	O
parts	O
to	O
one	O
another	O
.	O
</s>
<s>
DH-HMAC	O
is	O
defined	O
in	O
RFC	O
4650	O
.	O
</s>
<s>
RSA-R	O
(	O
MIKEY-RSA-R	O
)	O
(	O
Reverse	O
RSA	B-Architecture
)	O
:	O
The	O
Common	O
Secret	O
is	O
exchanged	O
with	O
the	O
help	O
of	O
public	B-Application
key	I-Application
encryption	I-Application
in	O
a	O
way	O
that	O
does	O
n't	O
require	O
any	O
PKI	B-Architecture
:	O
the	O
initiator	O
sends	O
its	O
public	O
RSA	B-Architecture
key	O
to	O
the	O
responder	O
,	O
which	O
responds	O
by	O
selecting	O
the	O
Common	O
Secret	O
and	O
then	O
send	O
it	O
back	O
to	O
the	O
initiator	O
encrypted	O
with	O
the	O
initiator	O
's	O
public	B-Application
key	I-Application
.	O
</s>
<s>
RSA-R	O
is	O
defined	O
in	O
RFC	O
4738	O
.	O
</s>
<s>
TICKET	O
(	O
MIKEY-TICKET	O
)	O
:	O
Ticket-Based	O
Modes	O
of	O
Key	O
Distribution	O
in	O
Multimedia	O
Internet	O
KEYing	O
(	O
MIKEY	B-Protocol
)	O
.	O
</s>
<s>
MIKEY-TICKET	O
is	O
defined	O
in	O
RFC	O
6043	O
.	O
</s>
<s>
IBAKE	O
(	O
MIKEY-IBAKE	O
)	O
:	O
Identity-Based	O
Authenticated	O
Key	O
Exchange	O
(	O
IBAKE	O
)	O
Mode	O
of	O
Key	O
Distribution	O
in	O
Multimedia	O
Internet	O
KEYing	O
(	O
MIKEY	B-Protocol
)	O
.	O
</s>
<s>
MIKEY-IBAKE	O
is	O
defined	O
in	O
RFC	O
6267	O
.	O
</s>
<s>
SAKKE	O
(	O
MIKEY-SAKKE	O
)	O
:	O
Sakai-Kasahara	O
Key	O
Encryption	O
in	O
Multimedia	O
Internet	O
KEYing	O
(	O
MIKEY	B-Protocol
)	O
.	O
</s>
<s>
MIKEY-SAKKE	O
is	O
defined	O
in	O
RFC	O
6509	O
.	O
</s>
<s>
The	O
majority	O
of	O
MIKEY	B-Protocol
methods	O
requires	O
the	O
initiator	O
to	O
send	O
a	O
message	O
to	O
participants	O
(	O
the	O
I_MESSAGE	O
)	O
,	O
and	O
the	O
receivers	O
to	O
respond	O
with	O
another	O
message	O
(	O
the	O
R_MESSAGE	O
)	O
.	O
</s>
<s>
MIKEY-SAKKE	O
does	O
not	O
require	O
an	O
R_MESSAGE	O
.	O
</s>
<s>
MIKEY	B-Protocol
messages	O
are	O
made	O
up	O
of	O
a	O
number	O
of	O
payloads	O
.	O
</s>
<s>
Each	O
payload	O
describes	O
the	O
next	O
payload	O
in	O
the	O
MIKEY	B-Protocol
message	O
.	O
</s>
<s>
In	O
this	O
way	O
the	O
MIKEY	B-Protocol
protocol	O
has	O
shown	O
it	O
is	O
flexible	O
to	O
being	O
extended	O
and	O
adapted	O
.	O
</s>
<s>
This	O
identifies	O
the	O
version	O
of	O
the	O
MIKEY	B-Protocol
protocol	O
,	O
the	O
method	O
used	O
(	O
data	O
type	O
)	O
,	O
whether	O
a	O
response	O
is	O
required	O
and	O
it	O
identifies	O
the	O
cryptographic	O
session	O
that	O
will	O
be	O
established	O
via	O
the	O
exchange	O
.	O
</s>
<s>
Further	O
payloads	O
are	O
defined	O
by	O
the	O
MIKEY	B-Protocol
method	O
in	O
use	O
.	O
</s>
<s>
Certificate	O
Hash	O
(	O
CHASH	O
)	O
-	O
a	O
hash	O
indicating	O
a	O
certificate	O
used	O
for	O
public-key	B-Application
encryption	I-Application
.	O
</s>
<s>
In	O
addition	O
to	O
this	O
,	O
the	O
MIKEY	B-Protocol
message	O
will	O
contain	O
at	O
least	O
one	O
payload	O
which	O
encapsulates	O
key	O
material	O
.	O
</s>
<s>
This	O
is	O
extended	O
by	O
RFC	O
4650	O
to	O
support	O
authenticated	O
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
(	O
DHHMAC	O
)	O
.	O
</s>
<s>
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
(	O
DH	O
)	O
-	O
this	O
contains	O
cryptographic	O
information	O
supporting	O
the	O
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
protocol	O
.	O
</s>
<s>
Envelope	O
Data	O
(	O
PKE	O
)	O
-	O
this	O
encapsulates	O
the	O
key	O
using	O
public	B-Application
key	I-Application
encryption	I-Application
.	O
</s>
<s>
Finally	O
,	O
the	O
MIKEY	B-Protocol
message	O
may	O
contain	O
an	O
authentication	O
payload	O
.	O
</s>
<s>
Signature	O
(	O
SIGN	O
)	O
-	O
a	O
signature	O
on	O
the	O
MIKEY	B-Protocol
message	O
.	O
</s>
