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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 java.security.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;

}