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  package java.security.interfaces;
  
  import java.security.*;
  
  /**
   * An interface to an object capable of generating DSA key pairs.
   *
   * <p>The {@code initialize} methods may each be called any number
   * of times. If no {@code 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.
   *
   * <p>Users wishing to indicate DSA-specific parameters, and to generate a key
   * pair suitable for use with the DSA algorithm typically
   *
   * <ol>
   *
   * <li>Get a key pair generator for the DSA algorithm by calling the
   * KeyPairGenerator {@code getInstance} method with "DSA"
   * as its argument.
   *
   * <li>Initialize the generator by casting the result to a DSAKeyPairGenerator
   * and calling one of the
   * {@code initialize} methods from this DSAKeyPairGenerator interface.
   *
   * <li>Generate a key pair by calling the {@code generateKeyPair}
   * method from the KeyPairGenerator class.
   *
   * </ol>
   *
   * <p>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 {@code initialize} method in this interface.
   * Algorithm-independent initialization using the {@code initialize} method
   * in the KeyPairGenerator
   * interface is all that is needed when you accept defaults for algorithm-specific
   * parameters.
   *
   * <p>Note: Some earlier implementations of this interface may not support
   * larger sizes of DSA parameters such as 2048 and 3072-bit.
   *
   * @see KeyPairGenerator
   */
  public interface DSAKeyPairGenerator {
  
      /**
       * 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.
       *
       * @param params the parameters to use to generate the keys.
       *
       * @param random the random bit source to use to generate key bits;
       * can be null.
       *
       * @exception InvalidParameterException if the {@code params}
       * value is invalid, null, or unsupported.
       */
     public void initialize(DSAParams params, 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.
       *
       * <p>If {@code 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.
       *
       * @param modlen the modulus length in bits. Valid values are any
       * multiple of 64 between 512 and 1024, inclusive, 2048, and 3072.
       *
       * @param random the random bit source to use to generate key bits;
       * can be null.
       *
       * @param genParams whether or not to generate new parameters for
       * the modulus length requested.
       *
       * @exception InvalidParameterException if {@code modlen} is
       * invalid, or unsupported, or if {@code genParams} is false and there
       * are no precomputed parameters for the requested modulus length.
       */
      public void initialize(int modlen, boolean genParams, SecureRandom random)
      throws InvalidParameterException;
  }
  