February 26, 2002
Practical Aspects of Modern Cryptography
9
The Digital Signature Algorithm
n
A signature
(
r
,
s
)
on
M
is verified as follows:
n
Compute
w
= 1/
s
mod
q
,
n
Compute
a
=
w
M mod
q
,
n
Compute
b
=
wr
mod
q
,
n
Compute
v
= (
g
a
y
b
mod
p
) mod
q
.
n
n
Accept the signature only if
v
=
r
.
n