DSAParams ("Entrust Authority Security Toolkit for the Java Platform")

java.lang.Object
- iaik.security.dsa.DSAParams

All Implemented Interfaces:

java.security.interfaces.DSAParams
```
public class DSAParams
extends java.lang.Object
implements java.security.interfaces.DSAParams
```
An implementation of DSA parameters that supports ASN.1 encoding. The Digital Signature Algorithm (DSA) only can be used for digital signing (respectively signature verifying). It cannot be used for data encryption.
NIST's Digital Signature Standard (DSS) specifies the DSA algorithm as public-key algorithm for being used for digital signing applications. For first calculating a hash value of any data to be signed, the Secure Hash Algorithm is proposed to be used along with the DSA algorithm.
The DSA algorithm uses a certain number of parameters:
- a prime number p, which length is a multiple of 64 bits lying between 512 and 1024 bits
- a 160-bit prime factor (q) of p-1
- a number h less than p-1 fulfilling (h^(p-1)/q)(mod p) > 1
- a number g calculated from g = (h^(p-1)/q)(mod p)
- a number x less than q
- a number y calculated from y = (g^x)(mod p)
p, q, g are made public, y forms the public key, and x represents the private key. The procedures of signing some message with one entity's private key, and verifying a signature using the signer's public key may be read up in "Applied Cryptography", Bruce Schneier, ISBN 0-471-59756-2).
This class represents the public parameters p (prime), q (sub-prime), and g and, for instance, may be used for algorithm specific initializing a KeyPairGenerator for generating DSA keys:
```
 DSAParams dsa_params = new DSAParams(p, q, g);
 dsa_key_gen.initialize(dsa_params, random);
 
```
(See http://java.sun.com/products/JDK/1.1/docs/guide/security/CryptoSpec.html)
Note:In versions of the toolkit 8.0 patch 184269 and earlier, the toolkit always encoded the DSA parameters with a bitlength as the initial ASN.1 component. This does not conform to RFC 3279. According to RFC 3279, it should be encoded as follows:
```
   Dss-Parms  ::=  SEQUENCE  {
       p            INTEGER,
       q            INTEGER,
       g            INTEGER  }
 
```
Therefore, the toolkit will now not encode the bit length in the default setting and will follow RFC 3279. Setting the system property specified below will allow the bit length to be encoded if this is required to be backward compatible with an existing application:
```
 -Diaik.security.dsa.DSAParams.encodeBitLengthParam=true
 
```
See Also:

KeyPairGenerator, KeyPair, DSAPublicKey, DSAPrivateKey, DSAKeyPairGenerator, DSAKeyFactory

Constructor Summary

Constructors
Constructor and Description
`DSAParams(ASN1Object obj)` Creates a new DSAParams object from the given ASN.1 Object.
`DSAParams(java.math.BigInteger p, java.math.BigInteger q, java.math.BigInteger g)` Creates a new DSAParams object from the given BigInteger parameters.
`DSAParams(java.security.interfaces.DSAParams params)` Creates a new DSAParams object from the given DSAParams

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`equals(java.lang.Object obj)` Compares this DSAParams object with the given DSAParams object.
`java.math.BigInteger`	`getG()` Returns the public base value `g` as BigInteger.
`java.math.BigInteger`	`getP()` Returns the public prime value `p` as BigInteger.
`java.math.BigInteger`	`getQ()` Returns the public sub-prime value `q` as BigInteger.
`int`	`hashCode()` Returns a hash code for this DSAParams object.
`ASN1Object`	`toASN1Object()` Returns this DSAParams object as ASN1Object of type SEQUENCE.
`java.lang.String`	`toString()` Returns a string that represents the contents of this DSAParams.

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - DSAParams
```
public DSAParams(java.math.BigInteger p,
                 java.math.BigInteger q,
                 java.math.BigInteger g)
```
    Creates a new DSAParams object from the given BigInteger parameters.
    
    Parameters:
    
    p - the public prime p (of a multiple length of 64 bits between 512 and 1024 bits)
    
    q - the public sub-prime q (a 160-bit prime factor of p-1)
    
    g - the public base g (=(h^(p-1)/q)(mod p) > 1, with h < p-1)
  - DSAParams
```
public DSAParams(java.security.interfaces.DSAParams params)
```
    Creates a new DSAParams object from the given DSAParams
    
    Parameters:
    
    params - the DSAParams
  - DSAParams
```
public DSAParams(ASN1Object obj)
          throws CodingException
```
    Creates a new DSAParams object from the given ASN.1 Object.
    This constructor may be used for parsing an already exisiting DSAParams object, supplied as ASN1Object that may have been created by calling toASN1Object.
    
    Parameters:
    
    obj - the DSA parameters as ASN1Object
    
    Throws:
    
    CodingException
- Method Detail
  - getP
```
public java.math.BigInteger getP()
```
    Returns the public prime value p as BigInteger.
    
    Specified by:
    
    getP in interface java.security.interfaces.DSAParams
    
    Returns:
    
    the prime value p
  - getQ
```
public java.math.BigInteger getQ()
```
    Returns the public sub-prime value q as BigInteger.
    
    Specified by:
    
    getQ in interface java.security.interfaces.DSAParams
    
    Returns:
    
    the sub-prime value q
  - getG
```
public java.math.BigInteger getG()
```
    Returns the public base value g as BigInteger.
    
    Specified by:
    
    getG in interface java.security.interfaces.DSAParams
    
    Returns:
    
    the base value g
  - toASN1Object
```
public ASN1Object toASN1Object()
```
    Returns this DSAParams object as ASN1Object of type SEQUENCE.
    The ASN1Object returned by this method may be used as parameter value when creating a DSAParams object using the DSAParams(ASN1Object obj) constructor.
    
    Returns:
    
    this DSAParams object as ASN1Object
  - hashCode
```
public int hashCode()
```
    Returns a hash code for this DSAParams object.
    
    Overrides:
    
    hashCode in class java.lang.Object
    
    Returns:
    
    the hash code
  - equals
```
public boolean equals(java.lang.Object obj)
```
    Compares this DSAParams object with the given DSAParams object.
    
    Overrides:
    
    equals in class java.lang.Object
    
    Parameters:
    
    obj - the other DSAParams object
    
    Returns:
    
    true, if the two DSAParams objects are equal, false otherwise
  - toString
```
public java.lang.String toString()
```
    Returns a string that represents the contents of this DSAParams.
    
    Overrides:
    
    toString in class java.lang.Object
    
    Returns:
    
    the string representation

Class DSAParams

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

DSAParams

DSAParams

DSAParams

Method Detail

getP

getQ

getG

toASN1Object

hashCode

equals

toString