<s>
In	O
cryptography	O
,	O
deniable	B-Protocol
authentication	I-Protocol
refers	O
to	O
message	B-Error_Name
authentication	I-Error_Name
between	O
a	O
set	O
of	O
participants	O
where	O
the	O
participants	O
themselves	O
can	O
be	O
confident	O
in	O
the	O
authenticity	B-Error_Name
of	O
the	O
messages	O
,	O
but	O
it	O
cannot	O
be	O
proved	O
to	O
a	O
third	O
party	O
after	O
the	O
event	O
.	O
</s>
<s>
In	O
practice	O
,	O
deniable	B-Protocol
authentication	I-Protocol
between	O
two	O
parties	O
can	O
be	O
achieved	O
through	O
the	O
use	O
of	O
message	B-Algorithm
authentication	I-Algorithm
codes	I-Algorithm
(	O
MACs	O
)	O
by	O
making	O
sure	O
that	O
if	O
an	O
attacker	O
is	O
able	O
to	O
decrypt	O
the	O
messages	O
,	O
they	O
would	O
also	O
know	O
the	O
MAC	O
key	O
as	O
part	O
of	O
the	O
protocol	O
,	O
and	O
would	O
thus	O
be	O
able	O
to	O
forge	O
authentic-looking	O
messages	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
the	O
Off-the-Record	B-Protocol
Messaging	I-Protocol
(	O
OTR	O
)	O
protocol	O
,	O
MAC	O
keys	O
are	O
derived	O
from	O
the	O
asymmetric	O
decryption	O
key	O
through	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
.	O
</s>
