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package com.sun.crypto.provider;

import javax.crypto.KeyGeneratorSpi;
import javax.crypto.SecretKey;
import javax.crypto.spec.DESedeKeySpec;
import java.security.SecureRandom;
import java.security.InvalidParameterException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.spec.AlgorithmParameterSpec;

This class generates a Triple DES key.
Author:
Jan Luehe/**
 * This class generates a Triple DES key.
 *
 * @author Jan Luehe
 *
 */

public final class DESedeKeyGenerator extends KeyGeneratorSpi {

    private SecureRandom random = null;
    private int keysize = 168;

    
Empty constructor
/**
     * Empty constructor
     */
    public DESedeKeyGenerator() {
    }

    
Initializes this key generator.
Params:
random – the source of randomness for this generator/**
     * 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.
Params:
params – the key generation parameters
random – the source of randomness for this key generator
Throws:
InvalidAlgorithmParameterException – if params is
inappropriate for this key generator/**
     * 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
                ("Triple DES key generation does not take any parameters");
    }

    
Initializes this key generator for a certain keysize, using the given
source of randomness.
Params:
keysize – the keysize. This is an algorithm-specific
metric specified in number of bits. A keysize with 112 bits of entropy
corresponds to a Triple DES key with 2 intermediate keys, and a keysize
with 168 bits of entropy corresponds to a Triple DES key with 3
intermediate keys.
random – the source of randomness for this key generator/**
     * 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. A keysize with 112 bits of entropy
     * corresponds to a Triple DES key with 2 intermediate keys, and a keysize
     * with 168 bits of entropy corresponds to a Triple DES key with 3
     * intermediate keys.
     * @param random the source of randomness for this key generator
     */
    protected void engineInit(int keysize, SecureRandom random) {
        if ((keysize != 112) && (keysize != 168)) {
            throw new InvalidParameterException("Wrong keysize: must be "
                                                + "equal to 112 or 168");
        }
        this.keysize = keysize;
        this.engineInit(random);
    }

    
Generates the Triple DES key.
Returns:
the new Triple DES key/**
     * Generates the Triple DES key.
     *
     * @return the new Triple DES key
     */
    protected SecretKey engineGenerateKey() {
        if (this.random == null) {
            this.random = SunJCE.RANDOM;
        }

        byte[] rawkey = new byte[DESedeKeySpec.DES_EDE_KEY_LEN];

        if (keysize == 168) {
            // 3 intermediate keys
            this.random.nextBytes(rawkey);

            // Do parity adjustment for each intermediate key
            DESKeyGenerator.setParityBit(rawkey, 0);
            DESKeyGenerator.setParityBit(rawkey, 8);
            DESKeyGenerator.setParityBit(rawkey, 16);
        } else {
            // 2 intermediate keys
            byte[] tmpkey = new byte[16];
            this.random.nextBytes(tmpkey);
            DESKeyGenerator.setParityBit(tmpkey, 0);
            DESKeyGenerator.setParityBit(tmpkey, 8);
            System.arraycopy(tmpkey, 0, rawkey, 0, tmpkey.length);
            // Copy the first 8 bytes into the last
            System.arraycopy(tmpkey, 0, rawkey, 16, 8);
            java.util.Arrays.fill(tmpkey, (byte)0x00);
        }

        DESedeKey desEdeKey = null;
        try {
            desEdeKey = new DESedeKey(rawkey);
        } catch (InvalidKeyException ike) {
            // this never happens
            throw new RuntimeException(ike.getMessage());
        }

        java.util.Arrays.fill(rawkey, (byte)0x00);

        return desEdeKey;
    }
}