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/**
 * As of "https://github.com/dfish3r/vt-crypt2 "CRYPT" (vt-crypt2) the source
 * code below the package "edu.vt.middleware.crypt" is dual licensed under both
 * the LGPL and Apache 2 license. As REFCODES.ORG source codes are also licensed
 * under the Apache License, v2.0 ("http://www.apache.org/licenses/TEXT-2.0"),
 * the according Apache 2 license principles are to be applied: "... The Apache
 * License is permissive; unlike copyleft licenses, it does not require a
 * derivative work of the software, or modifications to the original, to be
 * distributed using the same license. It still requires application of the same
 * license to all unmodified parts. In every licensed file, original copyright,
 * patent, trademark, and attribution notices must be preserved (excluding
 * notices that do not pertain to any part of the derivative works.) In every
 * licensed file changed, a notification must be added stating that changes have
 * been made to that file..." ("https://en.wikipedia.org/wiki/Apache_License")
 * 
 * "Software can be freely used, modified and distributed in any environment
 * under this license."
 * 
"A copy of the license must be included in the package." (→ see
 * refcodes-licensing dependency)
 * 
"Changes to the source code of the software under the Apache license do
 * not have to be sent back to the licensor."
 * 
"Own software that uses software under the Apache license does not have
 * to be under the Apache license."
 * 
"Your own software may only be called Apache if the Apache Foundation has
 * given written permission."
 * 
 * (freely translated from "https://de.wikipedia.org/wiki/Apache_License")
 */

/*
 * $Id: DSASignature.java 2744 2013-06-25 20:20:29Z dfisher $
 * 
 * Copyright (C) 2003-2013 Virginia Tech. All rights reserved.
 * 
 * SEE TEXT FOR MORE INFORMATION
 * 
 * Author: Middleware Services Email: [email protected] Version: $Revision: 2744
 * $ Updated: $Date: 2013-06-25 16:20:29 -0400 (Tue, 25 Jun 2013) $
 */
package edu.vt.middleware.crypt.signature;

import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.DSAParams;
import java.security.interfaces.DSAPrivateKey;
import java.security.interfaces.DSAPublicKey;

import org.bouncycastle.crypto.params.DSAParameters;
import org.bouncycastle.crypto.params.DSAPrivateKeyParameters;
import org.bouncycastle.crypto.params.DSAPublicKeyParameters;
import org.bouncycastle.crypto.signers.DSASigner;

import edu.vt.middleware.crypt.digest.DigestAlgorithm;
import edu.vt.middleware.crypt.digest.SHA1;

/**
 * Implements the DSA signature algorithm.
 *
 * @author Middleware Services
 * 
 * @version $Revision: 2744 $
 */
public class DSASignature extends AbstractDSASignature {

	/** Signature algorithm name. */
	private static final String ALGORITHM = "DSA";

	/**
	 * Creates a new DSA signature class that uses a SHA-1 for aMessage digest
	 * computation. This is the conventional DSA signature configuration.
	 */
	public DSASignature() {
		this( new SHA1() );
	}

	/**
	 * Creates a new DSA signature class that uses the given digest algorithm
	 * for aMessage digest computation.
	 *
	 * @param d Message digest algorithm.
	 */
	public DSASignature( final DigestAlgorithm d ) {
		super( ALGORITHM );
		digest = d;
		signer = new DSASigner();
	}

	/** {@inheritDoc} */
	@Override
	public void setSignKey( final PrivateKey key ) {
		if ( !DSAPrivateKey.class.isInstance( key ) ) {
			throw new IllegalArgumentException( "DSA private key required." );
		}
		super.setSignKey( key );
	}

	/** {@inheritDoc} */
	@Override
	public void setVerifyKey( final PublicKey key ) {
		if ( !DSAPublicKey.class.isInstance( key ) ) {
			throw new IllegalArgumentException( "DSA public key required." );
		}
		super.setVerifyKey( key );
	}

	/** {@inheritDoc} */
	@Override
	public void initSign() {
		if ( signKey == null ) {
			throw new IllegalStateException( "Sign key must be set prior to initialization." );
		}

		final DSAPrivateKey privKey = (DSAPrivateKey) signKey;
		final DSAParams params = privKey.getParams();
		final DSAPrivateKeyParameters bcParams = new DSAPrivateKeyParameters( privKey.getX(), new DSAParameters( params.getP(), params.getQ(), params.getG() ) );
		init( true, bcParams );
	}

	/** {@inheritDoc} */
	@Override
	public void initVerify() {
		if ( verifyKey == null ) {
			throw new IllegalStateException( "Verify key must be set prior to initialization." );
		}

		final DSAPublicKey pubKey = (DSAPublicKey) verifyKey;
		final DSAParams params = pubKey.getParams();
		final DSAPublicKeyParameters bcParams = new DSAPublicKeyParameters( pubKey.getY(), new DSAParameters( params.getP(), params.getQ(), params.getG() ) );
		init( false, bcParams );
	}
}