gnu.java.security.sig.dss
Class DSSSignature
- Cloneable, ISignature
The DSS (Digital Signature Standard) algorithm makes use of the following
parameters:
- p: A prime modulus, where
2L-1 < p < 2L
for 512 <= L
<= 1024
and L
a multiple of 64
. - q: A prime divisor of
p - 1
, where 2159
< q < 2160
. - g: Where
g = h(p-1)/q mod p
, where
h
is any integer with 1 < h < p - 1
such
that h (p-1)/q mod p > 1
(g
has order
q mod p
). - x: A randomly or pseudorandomly generated integer with
0 < x
< q
. - y:
y = gx mod p
. - k: A randomly or pseudorandomly generated integer with
0 < k
< q
.
The integers
p
,
q
, and
g
can be
public and can be common to a group of users. A user's private and public
keys are
x
and
y
, respectively. They are
normally fixed for a period of time. Parameters
x
and
k
are used for signature generation only, and must be kept
secret. Parameter
k
must be regenerated for each signature.
The signature of a message
M
is the pair of numbers
r
and
s
computed according to the equations below:
r = (gk mod p) mod q
ands = (k-1(SHA(M) + xr)) mod q
.
In the above,
k-1
is the multiplicative inverse of
k
,
mod q
; i.e.,
(k-1 k) mod q =
1
and
0 < k-1 < q
. The value of
SHA(M)
is a 160-bit string output by the Secure Hash Algorithm specified in FIPS
180. For use in computing
s
, this string must be converted to
an integer.
As an option, one may wish to check if
r == 0
or
s == 0
.
If either
r == 0
or
s == 0
, a new value of
k
should be generated and the signature should be recalculated
(it is extremely unlikely that
r == 0
or
s == 0
if
signatures are generated properly).
The signature is transmitted along with the message to the verifier.
References:
- Digital Signature
Standard (DSS), Federal Information Processing Standards Publication
186. National Institute of Standards and Technology.
clone , generateSignature , init , name , nextRandomBytes , setupForSigning , setupForVerification , setupSign , setupVerify , sign , update , update , verify , verifySignature |
clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
DSSSignature
public DSSSignature()
Trivial 0-arguments constructor.
clone
public Object clone()
This method may be called to create a new copy of the
Object. The typical behavior is as follows:
o == o.clone()
is falseo.getClass() == o.clone().getClass()
is trueo.equals(o)
is true
However, these are not strict requirements, and may
be violated if necessary. Of the three requirements, the
last is the most commonly violated, particularly if the
subclass does not override
Object.equals(Object)
.
If the Object you call clone() on does not implement
Cloneable
(which is a placeholder interface), then
a CloneNotSupportedException is thrown. Notice that
Object does not implement Cloneable; this method exists
as a convenience for subclasses that do.
Object's implementation of clone allocates space for the
new Object using the correct class, without calling any
constructors, and then fills in all of the new field values
with the old field values. Thus, it is a shallow copy.
However, subclasses are permitted to make a deep copy.
All array types implement Cloneable, and override
this method as follows (it should never fail):
public Object clone()
{
try
{
super.clone();
}
catch (CloneNotSupportedException e)
{
throw new InternalError(e.getMessage());
}
}
- clone in interface ISignature
- clone in interface BaseSignature
DSSSignature.java --
Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.
This file is a part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Classpath; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
USA
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module. An independent module is a module which is not derived from
or based on this library. If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so. If you do not wish to do so, delete this
exception statement from your version.