<s>
Yahalom	B-Protocol
is	O
an	O
authentication	O
and	O
secure	O
key-sharing	O
protocol	O
designed	O
for	O
use	O
on	O
an	O
insecure	O
network	O
such	O
as	O
the	O
Internet	O
.	O
</s>
<s>
Yahalom	B-Protocol
uses	O
a	O
trusted	O
arbitrator	O
to	O
distribute	O
a	O
shared	B-Algorithm
key	I-Algorithm
between	O
two	O
people	O
.	O
</s>
<s>
This	O
protocol	O
can	O
be	O
considered	O
as	O
an	O
improved	O
version	O
of	O
Wide	O
Mouth	O
Frog	O
protocol	O
(	O
with	O
additional	O
protection	O
against	O
man-in-the-middle	O
attack	O
)	O
,	O
but	O
less	O
secure	O
than	O
the	O
Needham	B-Protocol
–	I-Protocol
Schroeder	I-Protocol
protocol	I-Protocol
.	O
</s>
<s>
If	O
Alice	O
(	O
A	O
)	O
initiates	O
the	O
communication	O
to	O
Bob	O
(	O
B	O
)	O
with	O
S	O
is	O
a	O
server	O
trusted	O
by	O
both	O
parties	O
,	O
the	O
protocol	O
can	O
be	O
specified	O
as	O
follows	O
using	O
security	B-General_Concept
protocol	I-General_Concept
notation	I-General_Concept
:	O
</s>
