<s>
The	O
YAK	B-Protocol
is	O
a	O
public-key	O
authenticated	O
key-agreement	B-Protocol
protocol	I-Protocol
,	O
proposed	O
by	O
Feng	O
Hao	O
in	O
2010	O
.	O
</s>
<s>
It	O
is	O
claimed	O
to	O
be	O
the	O
simplest	O
authenticated	O
key	O
exchange	O
protocol	O
among	O
the	O
related	O
schemes	O
,	O
including	O
MQV	B-Protocol
,	O
HMQV	O
,	O
Station-to-Station	B-Protocol
protocol	I-Protocol
,	O
SSL/TLS	B-Protocol
etc	O
.	O
</s>
<s>
As	O
with	O
other	O
protocols	O
,	O
YAK	B-Protocol
normally	O
requires	O
a	O
Public	B-Architecture
Key	I-Architecture
Infrastructure	I-Architecture
to	O
distribute	O
authentic	O
public	O
keys	O
to	O
the	O
communicating	O
parties	O
.	O
</s>
<s>
The	O
security	O
of	O
YAK	B-Protocol
is	O
disputed	O
(	O
see	O
below	O
and	O
the	O
talk	O
page	O
)	O
.	O
</s>
<s>
Typically	O
a	O
Schnorr	B-Algorithm
group	I-Algorithm
is	O
used	O
.	O
</s>
<s>
In	O
general	O
,	O
YAK	B-Protocol
can	O
use	O
any	O
prime	O
order	O
group	O
that	O
is	O
suitable	O
for	O
public	O
key	O
cryptography	O
,	O
including	O
elliptic	O
curve	O
cryptography	O
.	O
</s>
<s>
Alice	O
selects	O
and	O
sends	O
out	O
together	O
with	O
a	O
zero-knowledge	B-Protocol
proof	I-Protocol
(	O
using	O
for	O
example	O
Schnorr	O
non-interactive	O
zero-knowledge	B-Protocol
proof	I-Protocol
as	O
described	O
in	O
RFC	O
8235	O
)	O
for	O
the	O
proof	O
of	O
the	O
exponent	O
.	O
</s>
<s>
Similarly	O
,	O
Bob	O
selects	O
and	O
sends	O
out	O
together	O
with	O
a	O
zero-knowledge	B-Protocol
proof	I-Protocol
for	O
the	O
proof	O
of	O
the	O
exponent	O
.	O
</s>
<s>
When	O
it	O
finishes	O
,	O
Alice	O
and	O
Bob	O
verify	O
the	O
received	O
zero-knowledge	B-Protocol
proofs	I-Protocol
.	O
</s>
<s>
With	O
the	O
same	O
keying	O
material	O
,	O
Alice	O
and	O
Bob	O
can	O
derive	O
a	O
session	O
key	O
using	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
:	O
.	O
</s>
<s>
The	O
use	O
of	O
well-established	O
zero-knowledge	B-Protocol
proof	I-Protocol
primitives	O
such	O
as	O
Schnorr	O
's	O
scheme	O
greatly	O
simplifies	O
the	O
security	O
proofs	O
.	O
</s>
<s>
Given	O
that	O
the	O
underlying	O
zero	B-Protocol
knowledge	I-Protocol
proof	I-Protocol
primitive	O
is	O
secure	O
,	O
the	O
YAK	B-Protocol
protocol	O
aims	O
to	O
satisfy	O
the	O
following	O
properties	O
.	O
</s>
<s>
The	O
security	O
claims	O
in	O
the	O
original	O
YAK	B-Protocol
paper	O
are	O
based	O
on	O
the	O
Computational	O
Diffie-Hellman	O
assumption	O
in	O
a	O
random	B-Application
oracle	I-Application
model	I-Application
.	O
</s>
<s>
In	O
2020	O
,	O
Mohammad	O
mentioned	O
that	O
YAK	B-Protocol
protocol	O
cannot	O
withstand	O
the	O
known	O
key	O
security	O
attack	O
which	O
leads	O
to	O
a	O
new	O
key	O
compromise	O
impersonation	O
attack	O
where	O
an	O
adversary	O
is	O
allowed	O
to	O
reveal	O
both	O
the	O
shared	O
static	O
secret	O
key	O
between	O
two	O
parties	O
and	O
the	O
ephemeral	O
private	O
key	O
of	O
the	O
initiator	O
.	O
</s>
<s>
The	O
author	O
also	O
proposed	O
an	O
improved	O
protocol	O
to	O
remedy	O
these	O
attacks	O
and	O
the	O
previous	O
attacks	O
mentioned	O
by	O
Toorani	O
on	O
the	O
YAK	B-Protocol
protocol	O
,	O
and	O
the	O
proposed	O
protocol	O
uses	O
a	O
verification	O
mechanism	O
that	O
provides	O
entity	O
authentication	O
and	O
key	O
confirmation	O
.	O
</s>
<s>
The	O
author	O
showed	O
that	O
the	O
proposed	O
protocol	O
is	O
secure	O
in	O
the	O
proposed	O
formal	O
security	O
model	O
under	O
the	O
gap	O
Diffie‐Hellman	O
assumption	O
and	O
the	O
random	B-Application
oracle	I-Application
assumption	O
.	O
</s>
<s>
Moreover	O
,	O
the	O
security	O
of	O
the	O
proposed	O
protocol	O
and	O
attacks	O
on	O
the	O
YAK	B-Protocol
protocol	O
were	O
verified	O
by	O
the	O
Scyther	O
tool	O
.	O
</s>
