package org.bouncycastle.crypto.generators;

import org.bouncycastle.crypto.KeyGenerationParameters;
import org.bouncycastle.crypto.params.DESedeParameters;

public class DESedeKeyGenerator
    extends DESKeyGenerator
{
    private static final int MAX_IT = 20;

    
initialise the key generator - if strength is set to zero
the key generated will be 192 bits in size, otherwise
strength can be 128 or 192 (or 112 or 168 if you don't count
parity bits), depending on whether you wish to do 2-key or 3-key
triple DES.
Params:
param – the parameters to be used for key generation/**
     * initialise the key generator - if strength is set to zero
     * the key generated will be 192 bits in size, otherwise
     * strength can be 128 or 192 (or 112 or 168 if you don't count
     * parity bits), depending on whether you wish to do 2-key or 3-key
     * triple DES.
     *
     * @param param the parameters to be used for key generation
     */
    public void init(
        KeyGenerationParameters param)
    {
        this.random = param.getRandom();
        this.strength = (param.getStrength() + 7) / 8;

        if (strength == 0 || strength == (168 / 8))
        {
            strength = DESedeParameters.DES_EDE_KEY_LENGTH;
        }
        else if (strength == (112 / 8))
        {
            strength = 2 * DESedeParameters.DES_KEY_LENGTH;
        }
        else if (strength != DESedeParameters.DES_EDE_KEY_LENGTH
                && strength != (2 * DESedeParameters.DES_KEY_LENGTH))
        {
            throw new IllegalArgumentException("DESede key must be "
                + (DESedeParameters.DES_EDE_KEY_LENGTH * 8) + " or "
                + (2 * 8 * DESedeParameters.DES_KEY_LENGTH)
                + " bits long.");
        }
    }

    public byte[] generateKey()
    {
        byte[]  newKey = new byte[strength];
        int     count = 0;

        do
        {
            random.nextBytes(newKey);

            DESedeParameters.setOddParity(newKey);
        }
        while (++count < MAX_IT && (DESedeParameters.isWeakKey(newKey, 0, newKey.length) || !DESedeParameters.isRealEDEKey(newKey, 0)));

        if (DESedeParameters.isWeakKey(newKey, 0, newKey.length) || !DESedeParameters.isRealEDEKey(newKey, 0))
        {
            throw new IllegalStateException("Unable to generate DES-EDE key");
        }

        return newKey;
    }
}