java.security.interfaces

## Interface DSAKeyPairGenerator

    public interface DSAKeyPairGenerator

An interface to an object capable of generating DSA key pairs.

The `initialize` methods may each be called any number of times. If no `initialize` method is called on a DSAKeyPairGenerator, the default is to generate 1024-bit keys, using precomputed p, q and g parameters and an instance of SecureRandom as the random bit source.

Users wishing to indicate DSA-specific parameters, and to generate a key pair suitable for use with the DSA algorithm typically

1. Get a key pair generator for the DSA algorithm by calling the KeyPairGenerator `getInstance` method with "DSA" as its argument.

2. Initialize the generator by casting the result to a DSAKeyPairGenerator and calling one of the `initialize` methods from this DSAKeyPairGenerator interface.

3. Generate a key pair by calling the `generateKeyPair` method from the KeyPairGenerator class.

Note: it is not always necessary to do do algorithm-specific initialization for a DSA key pair generator. That is, it is not always necessary to call an `initialize` method in this interface. Algorithm-independent initialization using the `initialize` method in the KeyPairGenerator interface is all that is needed when you accept defaults for algorithm-specific parameters.

Note: Some earlier implementations of this interface may not support larger sizes of DSA parameters such as 2048 and 3072-bit.

See Also:
  `KeyPairGenerator`

### Method Summary

Methods
`void` `initialize(DSAParams params, SecureRandom random)` Initializes the key pair generator using the DSA family parameters (p,q and g) and an optional SecureRandom bit source.
`void` `initialize(int modlen, boolean genParams, SecureRandom random)` Initializes the key pair generator for a given modulus length (instead of parameters), and an optional SecureRandom bit source.

### Method Detail

#### initialize

    void initialize(DSAParams params,
                  SecureRandom random)
                    throws InvalidParameterException

Initializes the key pair generator using the DSA family parameters (p,q and g) and an optional SecureRandom bit source. If a SecureRandom bit source is needed but not supplied, i.e. null, a default SecureRandom instance will be used.

Parameters:
  `params` - the parameters to use to generate the keys.
  `random` - the random bit source to use to generate key bits; can be null.
Throws:
  `InvalidParameterException` - if the `params` value is invalid, null, or unsupported.

#### initialize

    void initialize(int modlen,
                  boolean genParams,
                  SecureRandom random)
                    throws InvalidParameterException

Initializes the key pair generator for a given modulus length (instead of parameters), and an optional SecureRandom bit source. If a SecureRandom bit source is needed but not supplied, i.e. null, a default SecureRandom instance will be used.

If `genParams` is true, this method generates new p, q and g parameters. If it is false, the method uses precomputed parameters for the modulus length requested. If there are no precomputed parameters for that modulus length, an exception will be thrown. It is guaranteed that there will always be default parameters for modulus lengths of 512 and 1024 bits.

Parameters:
  `modlen` - the modulus length in bits. Valid values are any multiple of 64 between 512 and 1024, inclusive, 2048, and 3072.
  `random` - the random bit source to use to generate key bits; can be null.
  `genParams` - whether or not to generate new parameters for the modulus length requested.
Throws:
  `InvalidParameterException` - if `modlen` is invalid, or unsupported, or if `genParams` is false and there are no precomputed parameters for the requested modulus length.

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