package org.bouncycastle.crypto.generators;

import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.PBEParametersGenerator;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;

Generator for PBE derived keys and ivs as defined by PKCS 5 V2.0 Scheme 1.
Note this generator is limited to the size of the hash produced by the
digest used to drive it.

The document this implementation is based on can be found at

RSA's PKCS5 Page
/**
 * Generator for PBE derived keys and ivs as defined by PKCS 5 V2.0 Scheme 1.
 * Note this generator is limited to the size of the hash produced by the
 * digest used to drive it.
 * <p>
 * The document this implementation is based on can be found at
 * <a href=http://www.rsasecurity.com/rsalabs/pkcs/pkcs-5/index.html>
 * RSA's PKCS5 Page</a>
 */
public class PKCS5S1ParametersGenerator
    extends PBEParametersGenerator
{
    private Digest  digest;

    
Construct a PKCS 5 Scheme 1 Parameters generator. 
Params:
digest – the digest to be used as the source of derived keys./**
     * Construct a PKCS 5 Scheme 1 Parameters generator. 
     *
     * @param digest the digest to be used as the source of derived keys.
     */
    public PKCS5S1ParametersGenerator(
        Digest  digest)
    {
        this.digest = digest;
    }

    
the derived key function, the ith hash of the password and the salt.
/**
     * the derived key function, the ith hash of the password and the salt.
     */
    private byte[] generateDerivedKey()
    {
        byte[] digestBytes = new byte[digest.getDigestSize()];

        digest.update(password, 0, password.length);
        digest.update(salt, 0, salt.length);

        digest.doFinal(digestBytes, 0);
        for (int i = 1; i < iterationCount; i++)
        {
            digest.update(digestBytes, 0, digestBytes.length);
            digest.doFinal(digestBytes, 0);
        }

        return digestBytes;
    }

    
Generate a key parameter derived from the password, salt, and iteration
count we are currently initialised with.
Params:
keySize – the size of the key we want (in bits)
Throws:
IllegalArgumentException – if the key length larger than the base hash size.
Returns:
a KeyParameter object./**
     * Generate a key parameter derived from the password, salt, and iteration
     * count we are currently initialised with.
     *
     * @param keySize the size of the key we want (in bits)
     * @return a KeyParameter object.
     * @exception IllegalArgumentException if the key length larger than the base hash size.
     */
    public CipherParameters generateDerivedParameters(
        int keySize)
    {
        keySize = keySize / 8;

        if (keySize > digest.getDigestSize())
        {
            throw new IllegalArgumentException(
                   "Can't generate a derived key " + keySize + " bytes long.");
        }

        byte[]  dKey = generateDerivedKey();

        return new KeyParameter(dKey, 0, keySize);
    }

    
Generate a key with initialisation vector parameter derived from
the password, salt, and iteration count we are currently initialised
with.
Params:
keySize – the size of the key we want (in bits)
ivSize – the size of the iv we want (in bits)
Throws:
IllegalArgumentException – if keySize + ivSize is larger than the base hash size.
Returns:
a ParametersWithIV object./**
     * Generate a key with initialisation vector parameter derived from
     * the password, salt, and iteration count we are currently initialised
     * with.
     *
     * @param keySize the size of the key we want (in bits)
     * @param ivSize the size of the iv we want (in bits)
     * @return a ParametersWithIV object.
     * @exception IllegalArgumentException if keySize + ivSize is larger than the base hash size.
     */
    public CipherParameters generateDerivedParameters(
        int     keySize,
        int     ivSize)
    {
        keySize = keySize / 8;
        ivSize = ivSize / 8;

        if ((keySize + ivSize) > digest.getDigestSize())
        {
            throw new IllegalArgumentException(
                   "Can't generate a derived key " + (keySize + ivSize) + " bytes long.");
        }

        byte[]  dKey = generateDerivedKey();

        return new ParametersWithIV(new KeyParameter(dKey, 0, keySize), dKey, keySize, ivSize);
    }

    
Generate a key parameter for use with a MAC derived from the password,
salt, and iteration count we are currently initialised with.
Params:
keySize – the size of the key we want (in bits)
Throws:
IllegalArgumentException – if the key length larger than the base hash size.
Returns:
a KeyParameter object./**
     * Generate a key parameter for use with a MAC derived from the password,
     * salt, and iteration count we are currently initialised with.
     *
     * @param keySize the size of the key we want (in bits)
     * @return a KeyParameter object.
     * @exception IllegalArgumentException if the key length larger than the base hash size.
     */
    public CipherParameters generateDerivedMacParameters(
        int keySize)
    {
        return generateDerivedParameters(keySize);
    }
}