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package java.security;

import java.security.spec.AlgorithmParameterSpec;

/**
 * <p> This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
 * for the {@code KeyPairGenerator} class, which is used to generate
 * pairs of public and private keys.
 *
 * <p> All the abstract methods in this class must be implemented by each
 * cryptographic service provider who wishes to supply the implementation
 * of a key pair generator for a particular algorithm.
 *
 * <p> In case the client does not explicitly initialize the KeyPairGenerator
 * (via a call to an {@code initialize} method), each provider must
 * supply (and document) a default initialization.
 * See the Keysize Restriction sections of the
 * {@extLink security_guide_jdk_providers JDK Providers}
 * document for information on the KeyPairGenerator defaults used by
 * JDK providers.
 * However, note that defaults may vary across different providers.
 * Additionally, the default value for a provider may change in a future
 * version. Therefore, it is recommended to explicitly initialize the
 * KeyPairGenerator instead of relying on provider-specific defaults.
 *
 * @author Benjamin Renaud
 * @since 1.2
 *
 *
 * @see KeyPairGenerator
 * @see java.security.spec.AlgorithmParameterSpec
 */

public abstract class KeyPairGeneratorSpi {

 /**
 * Initializes the key pair generator for a certain keysize, using
 * the default parameter set.
 *
 * @param keysize the keysize. This is an
 * algorithm-specific metric, such as modulus length, specified in
 * number of bits.
 *
 * @param random the source of randomness for this generator.
 *
 * @exception InvalidParameterException if the {@code keysize} is not
 * supported by this KeyPairGeneratorSpi object.
 */
 public abstract void initialize(int keysize, SecureRandom random);

 /**
 * Initializes the key pair generator using the specified parameter
 * set and user-provided source of randomness.
 *
 * <p>This concrete method has been added to this previously-defined
 * abstract class. (For backwards compatibility, it cannot be abstract.)
 * It may be overridden by a provider to initialize the key pair
 * generator. Such an override
 * is expected to throw an InvalidAlgorithmParameterException if
 * a parameter is inappropriate for this key pair generator.
 * If this method is not overridden, it always throws an
 * UnsupportedOperationException.
 *
 * @param params the parameter set used to generate the keys.
 *
 * @param random the source of randomness for this generator.
 *
 * @exception InvalidAlgorithmParameterException if the given parameters
 * are inappropriate for this key pair generator.
 *
 * @since 1.2
 */
 public void initialize(AlgorithmParameterSpec params,
 SecureRandom random)
 throws InvalidAlgorithmParameterException {
 throw new UnsupportedOperationException();
 }

 /**
 * Generates a key pair. Unless an initialization method is called
 * using a KeyPairGenerator interface, algorithm-specific defaults
 * will be used. This will generate a new key pair every time it
 * is called.
 *
 * @return the newly generated {@code KeyPair}
 */
 public abstract KeyPair generateKeyPair();
}