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`java.lang.Object`

`gnu.java.security.sig.BaseSignature`

`gnu.java.security.sig.dss.DSSSignature`

**Implemented Interfaces:**- Cloneable, ISignature

`public class `**DSSSignature**

`extends BaseSignature`

The DSS (Digital Signature Standard) algorithm makes use of the following
parameters:

- p: A prime modulus, where
`2`

for^{L-1}< p < 2^{L}`512 <= L <= 1024`

and`L`

a multiple of`64`

. - q: A prime divisor of
`p - 1`

, where`2`

.^{159}< q < 2^{160} - g: Where
`g = h`

, where^{(p-1)}/q mod p`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 = g`

.^{x}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 = (g`

and^{k}mod p) mod q`s = (k`

.^{-1}(SHA(M) + xr)) mod q

In the above, `k`

is the multiplicative inverse of
^{-1}`k`

, `mod q`

; i.e., `(k`

and ^{-1} k) mod q =
1`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.

## Field Summary

### Fields inherited from class gnu.java.security.sig.BaseSignature

`md`

,`privateKey`

,`publicKey`

,`schemeName`

### Fields inherited from interface gnu.java.security.sig.ISignature

`SIGNER_KEY`

,`SOURCE_OF_RANDOMNESS`

,`VERIFIER_KEY`

## Constructor Summary

`DSSSignature()`

- Trivial 0-arguments constructor.

## Method Summary

`Object`

`clone()`

- Returns a clone copy of this instance.

`protected Object`

`protected void`

`protected void`

`static BigInteger[]`

`sign(DSAPrivateKey k, byte[] h)`

`static BigInteger[]`

`sign(DSAPrivateKey k, byte[] h, IRandom irnd)`

`static BigInteger[]`

`sign(DSAPrivateKey k, byte[] h, Random rnd)`

`static boolean`

`verify(DSAPublicKey k, byte[] h, BigInteger[] rs)`

`protected boolean`

`verifySignature(Object sig)`

### Methods inherited from class gnu.java.security.sig.BaseSignature

`clone`

,`generateSignature`

,`init`

,`name`

,`nextRandomBytes`

,`setupForSigning`

,`setupForVerification`

,`setupSign`

,`setupVerify`

,`sign`

,`update`

,`update`

,`verify`

,`verifySignature`

### Methods inherited from class java.lang.Object

`clone`

,`equals`

,`extends Object> getClass`

,`finalize`

,`hashCode`

,`notify`

,`notifyAll`

,`toString`

,`wait`

,`wait`

,`wait`

public Object clone()

Returns a clone copy of this instance.

Specified by:- clone in interface ISignature

Overrides:- clone in interface BaseSignature

Returns:- a clone copy of this instance.

protected Object generateSignature() throws IllegalStateException

Overrides:- generateSignature in interface BaseSignature

protected void setupForSigning(PrivateKey k) throws IllegalArgumentException

Overrides:- setupForSigning in interface BaseSignature

protected void setupForVerification(PublicKey k) throws IllegalArgumentException

Overrides:- setupForVerification in interface BaseSignature

protected boolean verifySignature(Object sig) throws IllegalStateException

Overrides:- verifySignature 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.
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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.
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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.
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permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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independent module, the terms and conditions of the license of that
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