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

java.lang.Object
- iaik.pkcs.pkcs8.PrivateKeyInfo
- - iaik.security.dsa.DSAPrivateKey

All Implemented Interfaces:

ASN1Type, java.io.Serializable, java.security.interfaces.DSAKey, java.security.interfaces.DSAPrivateKey, java.security.Key, java.security.PrivateKey, javax.security.auth.Destroyable
```
public class DSAPrivateKey
extends PrivateKeyInfo
implements java.security.interfaces.DSAPrivateKey, java.io.Serializable
```
An implementation of a DSA private key that supports ASN.1 encoding.
This class extends iaik.pkcs.pkcs8.PrivateKeyInfo for supporting the PKCS#8 Private Key Information Standard for the DSA private keys. This class implements the java.security.interfaces.DSAPrivateKey interface for providing the functionality of a private key used for signing some data within the DSA algorithm.
The Digital Signature Algorithm (DSA) only can be used for digital signing (respectively signature verifying). It cannot be used for data encryption.
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).
An application wishing to create a DSAPrivateKey to be used for data signing with the DSA algorithm, uses a proper getInstance method of the java.security.KeyPairGenerator class, which subsequently maybe casted to DSAKeyPairGenerator for performing an algorithm-specific initialization with proper DSA parameters. If an algorithm-specific initialization is not required, the cast to DSAKeyPairGenerator can be omitted.
Generally four steps have to be performed for creating a DSAPrivateKey by using a proper KeyPairGenerator:
- First the KeyPairGenerator has to be instantiated thereby specifying the application's intention to create keys for use within the DSA algorithm:
```
 KeyPairGenerator key_gen = KeyPairGenerator.getInstance("DSA", "IAIK");
 
```
- Second, the KeyPairGenerator just created may be initialized using a proper initialize method. For initializing the generator to create keys with a modulus length of, e.g., 1024 bits, this can be explicitly specified (1024 bits also is the default value for the modulus length when not explicitly initializing the generator):
```
 key_gen.initialize(1024);
 
```
- Third the key pair is created by calling generateKeyPair():
  KeyPair key_pair = key_gen.generateKeyPair();
- And finally, if there is need for the DSA private key, it has to be obtained from the key pair just created:
```
 DSAPrivateKey dsa_priv_key = (DSAPrivateKey)key_pair.getPrivate();
 
```
For performing an algorithm-specific initialization with particular DSA parameters (which may be an instance of DSAParams representing the public parameter values p, q and g), an explicit cast of the KeyPairGenerator will be necessary for obtaining a specific DSAKeyPairGenerator to be initialized with the desired DSA parameters:
```
 DSAKeyPairGenerator dsa_key_gen = (DSAKeyPairGenerator)key_gen;
 dsa_key_gen.initialize(dsa_params, random);
 
```
(where random denotes some random seed)
Guidelines on how to create some key using a KeyPairGenerator can be found in http://java.sun.com/products/JDK/1.1/docs/guide/security/CryptoSpec.html.
See Also:

PrivateKeyInfo, DSAPrivateKey, KeyPairGenerator, KeyPair, DSAPublicKey, DSAKeyPairGenerator, DSAKeyFactory, DSAParams, Serialized Form

Field Summary
- Fields inherited from class iaik.pkcs.pkcs8.PrivateKeyInfo
  private_key_algorithm, private_key_info
- Fields inherited from interface java.security.interfaces.DSAPrivateKey
  serialVersionUID

Constructor Summary

Constructors
Constructor and Description
`DSAPrivateKey(ASN1Object obj)` Creates a new DSAPrivateKey from the given ASN.1 object.
`DSAPrivateKey(java.math.BigInteger x, java.math.BigInteger p, java.math.BigInteger q, java.math.BigInteger g)` Creates a new DSAPrivateKey from the given BigInteger values.
`DSAPrivateKey(java.math.BigInteger x, java.security.interfaces.DSAParams dsaParams)` Creates a new DSAPrivateKey from given private key value x and DSA parameters
`DSAPrivateKey(byte[] key)` Creates a new DSAPrivateKey from the given DER encoded byte array.
`DSAPrivateKey(java.security.interfaces.DSAPrivateKey privKey)` Creates a new DSAPrivateKey from the given DSAPrivateKey.
`DSAPrivateKey(java.security.spec.DSAPrivateKeySpec keySpec)` Creates a new DSAPrivateKey from the given DSAPrivateKeySpec representing the DSA private key value x, and the public values p, q and g.
`DSAPrivateKey(java.io.InputStream is)` Creates a new DSAPrivateKey from an InputStream.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected void`	`decode(byte[] privateKey)` Decodes a DER encoded DSA private key.
`protected byte[]`	`encode()` Returns this DSA private key as DER encoded byte array.
`boolean`	`equals(java.lang.Object obj)` Compares this DSAPrivateKey with the given DSAPrivateKey.
`java.lang.String`	`getAlgorithm()` Returns the name of the appertaining algorithm.
`java.security.interfaces.DSAParams`	`getParams()` Returns the DSA parameters prime p, sub-prime q and base g as DSAParams.
`java.math.BigInteger`	`getX()` Returns the private key value x.
`int`	`hashCode()` Returns a hash code for this DSAPrivateKey object.
`java.lang.String`	`toString()` Returns a string that represents the contents of this private key.

Methods inherited from class iaik.pkcs.pkcs8.PrivateKeyInfo
createPrivateKeyInfo, decode, getEncoded, getFormat, getPrivateKey, getPrivateKey, toASN1Object, writeTo

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

Methods inherited from interface java.security.Key
getEncoded, getFormat

Methods inherited from interface javax.security.auth.Destroyable
destroy, isDestroyed

- Constructor Detail
  - DSAPrivateKey
```
public DSAPrivateKey(java.math.BigInteger x,
                     java.security.interfaces.DSAParams dsaParams)
```
    Creates a new DSAPrivateKey from given private key value x and DSA parameters
    
    Parameters:
    
    x - the BigInteger value representing the DSA private key value
    
    dsaParams - the public DSA parameters p (prime), q (sub-prime) and g (base) as DSAParams
    
    See Also:
    
    DSAParams
  - DSAPrivateKey
```
public DSAPrivateKey(java.math.BigInteger x,
                     java.math.BigInteger p,
                     java.math.BigInteger q,
                     java.math.BigInteger g)
```
    Creates a new DSAPrivateKey from the given BigInteger values.
    
    Parameters:
    
    x - the BigInteger value representing the DSA private key
    
    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)
  - DSAPrivateKey
```
public DSAPrivateKey(java.security.spec.DSAPrivateKeySpec keySpec)
```
    Creates a new DSAPrivateKey from the given DSAPrivateKeySpec representing the DSA private key value x, and the public values p, q and g.
    
    Parameters:
    
    keySpec - the DSAPrivateKeySpec representing the private key value x, the prime p, the sub-prime q, and the base g
    
    See Also:
    
    DSAPrivateKeySpec
  - DSAPrivateKey
```
public DSAPrivateKey(java.security.interfaces.DSAPrivateKey privKey)
```
    Creates a new DSAPrivateKey from the given DSAPrivateKey.
    
    Parameters:
    
    privKey - the DSAPrivateKey
  - DSAPrivateKey
```
public DSAPrivateKey(byte[] key)
              throws java.security.InvalidKeyException
```
    Creates a new DSAPrivateKey from the given DER encoded byte array.
    
    Parameters:
    
    key - the byte array holding the DER encoded private key ASN.1 data structure
    
    Throws:
    
    java.security.InvalidKeyException - if something is wrong with the encoding of the key
  - DSAPrivateKey
```
public DSAPrivateKey(ASN1Object obj)
              throws java.security.InvalidKeyException
```
    Creates a new DSAPrivateKey from the given ASN.1 object. The supplied ASN1Object represents a PKCS#8 PrivateKeyInfo holding the DSA private key.
    
    Parameters:
    
    obj - the private key ASN.1 data structure
    
    Throws:
    
    java.security.InvalidKeyException - if something is wrong with the key encoding
  - DSAPrivateKey
```
public DSAPrivateKey(java.io.InputStream is)
              throws java.security.InvalidKeyException,
                     java.io.IOException
```
    Creates a new DSAPrivateKey from an InputStream.
    This constructor may be used for parsing an already exisiting DSA private key, wrapped into a PKCS#8 PrivateKeyInfo that is supplied as DER encoded byte array.
    
    Parameters:
    
    is - the input stream with the data to be read to initialize the private key
    
    Throws:
    
    java.security.InvalidKeyException - if something is wrong with the key encoding
    
    java.io.IOException - if an I/O error occurs
- Method Detail
  - getX
```
public java.math.BigInteger getX()
```
    Returns the private key value x.
    
    Specified by:
    
    getX in interface java.security.interfaces.DSAPrivateKey
    
    Returns:
    
    the private key value x
  - getParams
```
public java.security.interfaces.DSAParams getParams()
```
    Returns the DSA parameters prime p, sub-prime q and base g as DSAParams.
    
    Specified by:
    
    getParams in interface java.security.interfaces.DSAKey
    
    Returns:
    
    the DSAParams representing prime p, sub-prime q and base g
  - encode
```
protected byte[] encode()
```
    Returns this DSA private key as DER encoded byte array.
    This method is protected and typically will not be used by an application. Rather it is used by the parent PKCS#8 PrivateKeyInfo class for encoding the inherent DSA private key.
    
    Specified by:
    
    encode in class PrivateKeyInfo
    
    Returns:
    
    the DSA private key as a DER encoded ASN.1 data structure
  - decode
```
protected void decode(byte[] privateKey)
               throws java.security.InvalidKeyException
```
    Decodes a DER encoded DSA private key. From the given DER encoded byte array an ASN.1 object is created and parsed for the private key value x.
    This method is protected and typically will not be used by an application. Rather it is used by the parent PKCS#8 PrivateKeyInfo class for decoding the inherent DSA private key.
    
    Specified by:
    
    decode in class PrivateKeyInfo
    
    Parameters:
    
    privateKey - the DSA private key as DER encoded byte array
    
    Throws:
    
    java.security.InvalidKeyException - if the given key is not a DSA private key
  - getAlgorithm
```
public java.lang.String getAlgorithm()
```
    Returns the name of the appertaining algorithm.
    
    Specified by:
    
    getAlgorithm in interface java.security.Key
    
    Specified by:
    
    getAlgorithm in class PrivateKeyInfo
    
    Returns:
    
    the string "DSA"
  - hashCode
```
public int hashCode()
```
    Returns a hash code for this DSAPrivateKey object.
    
    Overrides:
    
    hashCode in class java.lang.Object
    
    Returns:
    
    the hash code
  - equals
```
public boolean equals(java.lang.Object obj)
```
    Compares this DSAPrivateKey with the given DSAPrivateKey.
    
    Overrides:
    
    equals in class PrivateKeyInfo
    
    Parameters:
    
    obj - the other DSAPrivateKey
    
    Returns:
    
    true, if the two private key objects are equal, false otherwise
  - toString
```
public java.lang.String toString()
```
    Returns a string that represents the contents of this private key.
    
    Overrides:
    
    toString in class PrivateKeyInfo
    
    Returns:
    
    the string representation

Class DSAPrivateKey

Field Summary

Fields inherited from class iaik.pkcs.pkcs8.PrivateKeyInfo

Fields inherited from interface java.security.interfaces.DSAPrivateKey

Constructor Summary

Method Summary

Methods inherited from class iaik.pkcs.pkcs8.PrivateKeyInfo

Methods inherited from class java.lang.Object

Methods inherited from interface java.security.Key

Methods inherited from interface javax.security.auth.Destroyable

Constructor Detail

DSAPrivateKey

DSAPrivateKey

DSAPrivateKey

DSAPrivateKey

DSAPrivateKey

DSAPrivateKey

DSAPrivateKey

Method Detail

getX

getParams

encode

decode

getAlgorithm

hashCode

equals

toString