<s>
Authenticated	B-Protocol
Identity	I-Protocol
Body	I-Protocol
or	O
AIB	O
is	O
a	O
method	O
allowing	O
parties	O
in	O
a	O
network	O
to	O
share	O
authenticated	O
identity	O
thereby	O
increasing	O
the	O
integrity	O
of	O
their	O
SIP	B-Application
communications	O
.	O
</s>
<s>
AIBs	O
extend	O
other	O
authentication	O
methods	O
like	O
S/MIME	O
to	O
provide	O
a	O
more	O
specific	O
mechanism	O
to	O
introduce	O
integrity	O
to	O
SIP	B-Application
transmissions	O
.	O
</s>
<s>
Parties	O
transmitting	O
AIBs	O
cryptographically	O
sign	O
a	O
subset	O
of	O
SIP	B-Application
message	O
headers	O
,	O
and	O
such	O
signatures	O
assert	O
the	O
message	O
originator	O
's	O
identity	O
.	O
</s>
<s>
To	O
meet	O
requirements	O
of	O
reference	O
integrity	O
(	O
for	O
example	O
in	O
defending	O
against	O
replay	O
attacks	O
)	O
additional	O
SIP	B-Application
message	O
headers	O
such	O
as	O
'	O
Date	O
 '	O
and	O
'	O
Contact	O
 '	O
may	O
be	O
optionally	O
included	O
in	O
the	O
AIB	O
.	O
</s>
<s>
However	O
,	O
for	O
some	O
networks	O
(	O
in	O
which	O
there	O
are	O
federations	B-Protocol
of	O
trusted	O
hosts	O
under	O
a	O
common	O
policy	O
)	O
,	O
the	O
widespread	O
distribution	O
of	O
a	O
decryption	O
key	O
could	O
be	O
appropriate	O
.	O
</s>
