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Library for performing common cryptographic operations

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/*
  $Id: PBKDF2Parameters.java 1818 2011-02-08 19:19:09Z dfisher $

  Copyright (C) 2007-2011 Virginia Tech.
  All rights reserved.

  SEE LICENSE FOR MORE INFORMATION

  Author:  Middleware Services
  Email:   [email protected]
  Version: $Revision: 1818 $
  Updated: $Date: 2011-02-08 14:19:09 -0500 (Tue, 08 Feb 2011) $
*/
package edu.vt.middleware.crypt.pkcs;

import edu.vt.middleware.crypt.util.DERHelper;
import org.bouncycastle.asn1.DERSequence;

/**
 * Describes the PBKDF2-params type defined in PKCS#5v2.
 *
 * @author  Middleware Services
 * @version  $Revision: 1818 $
 */
public class PBKDF2Parameters extends PBEParameter
{

  /** Length of derived key in number of octets (bytes). */
  private int length;


  /**
   * Creates a new PBKDF2 parameter with given values.
   *
   * @param  saltBytes  Bytes of digest salt.
   * @param  iterations  Number of iterations of mixing function.
   */
  public PBKDF2Parameters(final byte[] saltBytes, final int iterations)
  {
    super(saltBytes, iterations);
  }


  /**
   * Creates a new PBKDF2 parameter with given values.
   *
   * @param  saltBytes  Bytes of digest salt.
   * @param  iterations  Number of iterations of mixing function.
   * @param  keyByteLength  Size of derived key in bytes (octets).
   */
  public PBKDF2Parameters(
    final byte[] saltBytes,
    final int iterations,
    final int keyByteLength)
  {
    super(saltBytes, iterations);
    setLength(keyByteLength);
  }


  /**
   * Decodes a DER sequence of PBKDF2 parameters into an instance of this class.
   *
   * @param  params  PBKDF2 parameters as a DER sequence.
   *
   * @return  Equivalent instance of {@link PBKDF2Parameters}.
   */
  public static PBKDF2Parameters decode(final DERSequence params)
  {
    final DERSequence kdfSeq = (DERSequence) params.getObjectAt(1);
    final PBKDF2Parameters instance = new PBKDF2Parameters(
      DERHelper.asOctets(kdfSeq.getObjectAt(0)),
      DERHelper.asInt(kdfSeq.getObjectAt(1)));
    if (kdfSeq.size() > 2) {
      instance.setLength(DERHelper.asInt(kdfSeq.getObjectAt(2)) * 8);
    }
    return instance;
  }


  /**
   * Gets the length of the derived key.
   *
   * @return  Length of derived key in bytes (octets).
   */
  public int getLength()
  {
    return length;
  }


  /**
   * Sets the length of the derived key.
   *
   * @param  byteLength  Length of derived key in bytes (octets).
   */
  public void setLength(final int byteLength)
  {
    if (byteLength < 1) {
      throw new IllegalArgumentException(
        "Key length must be positive integer.");
    }
    this.length = byteLength;
  }
}