<s>
The	O
ElGamal	B-Algorithm
signature	I-Algorithm
scheme	I-Algorithm
is	O
a	O
digital	O
signature	O
scheme	O
which	O
is	O
based	O
on	O
the	O
difficulty	O
of	O
computing	O
discrete	O
logarithms	O
.	O
</s>
<s>
It	O
was	O
described	O
by	O
Taher	O
Elgamal	B-Algorithm
in	O
1985	O
.	O
</s>
<s>
The	O
ElGamal	B-Algorithm
signature	O
algorithm	O
is	O
rarely	O
used	O
in	O
practice	O
.	O
</s>
<s>
The	O
ElGamal	B-Algorithm
signature	I-Algorithm
scheme	I-Algorithm
must	O
not	O
be	O
confused	O
with	O
ElGamal	B-Algorithm
encryption	I-Algorithm
which	O
was	O
also	O
invented	O
by	O
Taher	O
Elgamal	B-Algorithm
.	O
</s>
<s>
The	O
ElGamal	B-Algorithm
signature	I-Algorithm
scheme	I-Algorithm
is	O
a	O
digital	O
signature	O
scheme	O
based	O
on	O
the	O
algebraic	O
properties	O
of	O
modular	O
exponentiation	O
,	O
together	O
with	O
the	O
discrete	O
logarithm	O
problem	O
.	O
</s>
<s>
The	O
ElGamal	B-Algorithm
signature	I-Algorithm
scheme	I-Algorithm
was	O
described	O
by	O
Taher	O
Elgamal	B-Algorithm
in	O
1985	O
.	O
</s>
<s>
Choose	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
with	O
output	O
length	O
bits	O
.	O
</s>
<s>
If	O
,	O
only	O
the	O
leftmost	O
bits	O
of	O
the	O
hash	B-Algorithm
output	O
are	O
used	O
.	O
</s>
<s>
A	O
third	O
party	O
can	O
forge	O
signatures	O
either	O
by	O
finding	O
the	O
signer	O
's	O
secret	O
key	O
x	O
or	O
by	O
finding	O
collisions	O
in	O
the	O
hash	B-Algorithm
function	I-Algorithm
.	O
</s>
<s>
The	O
original	O
paper	O
did	O
not	O
include	O
a	O
hash	B-Algorithm
function	I-Algorithm
as	O
a	O
system	O
parameter	O
.	O
</s>
