edu.vt.middleware.crypt.pbe.AbstractPKCSKeyGenerator.java Source code

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Here is the source code for edu.vt.middleware.crypt.pbe.AbstractPKCSKeyGenerator.java

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/*
  $Id$
    
  Copyright (C) 2003-2013 Virginia Tech.
  All rights reserved.
    
  SEE LICENSE FOR MORE INFORMATION
    
  Author:  Middleware Services
  Email:   middleware@vt.edu
  Version: $Revision$
  Updated: $Date$
*/
package edu.vt.middleware.crypt.pbe;

import org.bouncycastle.crypto.PBEParametersGenerator;
import org.bouncycastle.crypto.params.KeyParameter;

/**
 * Base class for all PKCS key generators that use a key derivation function
 * that performs iterative hashing operations on a salted password.
 *
 * <p>For a key derivation function <em>f</em>, the following formula applies:
 * <br>
 * <code>derivedKey = f(password, salt, iterations)</code></p>
 *
 * <p>Classes derived from this class are <em>NOT</em> thread safe.</p>
 *
 * @author  Middleware Services
 * @version  $Revision$
 */
public abstract class AbstractPKCSKeyGenerator implements KeyGenerator {

    /** Default number of iterations taken from examples in PKCS#5v2. */
    public static final int DEFAULT_ITERATION_COUNT = 1000;

    /** Key derifcation function salt. */
    protected byte[] salt;

    /** Key derifcation function iteration count. */
    protected int iterationCount = DEFAULT_ITERATION_COUNT;

    /** {@inheritDoc} */
    public byte[] generate(final char[] password, final int size) {
        if (size < 1) {
            throw new IllegalArgumentException("Size must be positive integer.");
        }

        final PBEParametersGenerator generator = newParamGenerator();
        generator.init(toBytes(password), salt, iterationCount);

        final KeyParameter p = (KeyParameter) generator.generateDerivedParameters(size);
        return p.getKey();
    }

    /**
     * Gets the key derivation function iteration count.
     *
     * @param  count  Iteration count. MUST be positive integer.
     */
    protected void setIterationCount(final int count) {
        if (count < 1) {
            throw new IllegalArgumentException("Count must be positive integer.");
        }
        this.iterationCount = count;
    }

    /**
     * Creates a new BC parameter generator instance.
     *
     * @return  New parameter generator.
     */
    protected abstract PBEParametersGenerator newParamGenerator();

    /**
     * Converts password characters to bytes in implementation-dependent fashion.
     *
     * @param  password  Password to convert.
     *
     * @return  Password bytes.
     */
    protected abstract byte[] toBytes(char[] password);
}