/*

 * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package com.sun.crypto.provider;

import java.security.SecureRandom;

import java.security.InvalidParameterException;

import java.security.InvalidAlgorithmParameterException;

import java.security.spec.AlgorithmParameterSpec;

import javax.crypto.KeyGeneratorSpi;

import javax.crypto.SecretKey;

import javax.crypto.spec.SecretKeySpec;

/**

 * This class generates a secret key for use with the HMAC-SHA1 algorithm.

 *

 * @author Jan Luehe

 *

 */

public final class HmacSHA1KeyGenerator extends KeyGeneratorSpi {

    private SecureRandom random = null;

    private int keysize = 64; // default keysize (in number of bytes)

    /**

     * Empty constructor

     */

    public HmacSHA1KeyGenerator() {

    }

    /**

     * Initializes this key generator.

     *

     * @param random the source of randomness for this generator

     */

    protected void engineInit(SecureRandom random) {

        this.random = random;

    }

    /**

     * Initializes this key generator with the specified parameter

     * set and a user-provided source of randomness.

     *

     * @param params the key generation parameters

     * @param random the source of randomness for this key generator

     *

     * @exception InvalidAlgorithmParameterException if <code>params</code> is

     * inappropriate for this key generator

     */

    protected void engineInit(AlgorithmParameterSpec params,

                              SecureRandom random)

        throws InvalidAlgorithmParameterException

    {

        throw new InvalidAlgorithmParameterException

            ("HMAC-SHA1 key generation does not take any parameters");

    }

    /**

     * Initializes this key generator for a certain keysize, using the given

     * source of randomness.

     *

     * @param keysize the keysize. This is an algorithm-specific

     * metric specified in number of bits.

     * @param random the source of randomness for this key generator

     */

    protected void engineInit(int keysize, SecureRandom random) {

        this.keysize = (keysize+7) / 8;

        this.engineInit(random);

    }

    /**

     * Generates an HMAC-SHA1 key.

     *

     * @return the new HMAC-SHA1 key

     */

    protected SecretKey engineGenerateKey() {

        if (this.random == null) {

            this.random = SunJCE.getRandom();

        }

        byte[] keyBytes = new byte[this.keysize];

        this.random.nextBytes(keyBytes);

        return new SecretKeySpec(keyBytes, "HmacSHA1");

    }

}