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Library for performing common cryptographic operations
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/*
  $Id$

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

  SEE LICENSE FOR MORE INFORMATION

  Author:  Middleware Services
  Email:   [email protected]
  Version: $Revision$
  Updated: $Date$
*/
package edu.vt.middleware.crypt.symmetric;

import java.security.spec.AlgorithmParameterSpec;
import javax.crypto.spec.RC2ParameterSpec;

/**
 * Provider of symmetric encryption/decryption operations using RC2 cipher.
 *
 * @author  Middleware Services
 * @version  $Revision: 3 $
 */

public class RC2 extends SymmetricAlgorithm
{

  /** Algorithm name. */
  public static final String ALGORITHM = "RC2";

  /**
   * EKB table mentioned in RFC2268 section 6. Maps effective bits to RC2Version
   * code.
   */
  private static final int[] EFFECTIVE_BITS_TO_VERSION = new int[] {
    0xbd, 0x56, 0xea, 0xf2, 0xa2, 0xf1, 0xac, 0x2a,
    0xb0, 0x93, 0xd1, 0x9c, 0x1b, 0x33, 0xfd, 0xd0,
    0x30, 0x04, 0xb6, 0xdc, 0x7d, 0xdf, 0x32, 0x4b,
    0xf7, 0xcb, 0x45, 0x9b, 0x31, 0xbb, 0x21, 0x5a,
    0x41, 0x9f, 0xe1, 0xd9, 0x4a, 0x4d, 0x9e, 0xda,
    0xa0, 0x68, 0x2c, 0xc3, 0x27, 0x5f, 0x80, 0x36,
    0x3e, 0xee, 0xfb, 0x95, 0x1a, 0xfe, 0xce, 0xa8,
    0x34, 0xa9, 0x13, 0xf0, 0xa6, 0x3f, 0xd8, 0x0c,
    0x78, 0x24, 0xaf, 0x23, 0x52, 0xc1, 0x67, 0x17,
    0xf5, 0x66, 0x90, 0xe7, 0xe8, 0x07, 0xb8, 0x60,
    0x48, 0xe6, 0x1e, 0x53, 0xf3, 0x92, 0xa4, 0x72,
    0x8c, 0x08, 0x15, 0x6e, 0x86, 0x00, 0x84, 0xfa,
    0xf4, 0x7f, 0x8a, 0x42, 0x19, 0xf6, 0xdb, 0xcd,
    0x14, 0x8d, 0x50, 0x12, 0xba, 0x3c, 0x06, 0x4e,
    0xec, 0xb3, 0x35, 0x11, 0xa1, 0x88, 0x8e, 0x2b,
    0x94, 0x99, 0xb7, 0x71, 0x74, 0xd3, 0xe4, 0xbf,
    0x3a, 0xde, 0x96, 0x0e, 0xbc, 0x0a, 0xed, 0x77,
    0xfc, 0x37, 0x6b, 0x03, 0x79, 0x89, 0x62, 0xc6,
    0xd7, 0xc0, 0xd2, 0x7c, 0x6a, 0x8b, 0x22, 0xa3,
    0x5b, 0x05, 0x5d, 0x02, 0x75, 0xd5, 0x61, 0xe3,
    0x18, 0x8f, 0x55, 0x51, 0xad, 0x1f, 0x0b, 0x5e,
    0x85, 0xe5, 0xc2, 0x57, 0x63, 0xca, 0x3d, 0x6c,
    0xb4, 0xc5, 0xcc, 0x70, 0xb2, 0x91, 0x59, 0x0d,
    0x47, 0x20, 0xc8, 0x4f, 0x58, 0xe0, 0x01, 0xe2,
    0x16, 0x38, 0xc4, 0x6f, 0x3b, 0x0f, 0x65, 0x46,
    0xbe, 0x7e, 0x2d, 0x7b, 0x82, 0xf9, 0x40, 0xb5,
    0x1d, 0x73, 0xf8, 0xeb, 0x26, 0xc7, 0x87, 0x97,
    0x25, 0x54, 0xb1, 0x28, 0xaa, 0x98, 0x9d, 0xa5,
    0x64, 0x6d, 0x7a, 0xd4, 0x10, 0x81, 0x44, 0xef,
    0x49, 0xd6, 0xae, 0x2e, 0xdd, 0x76, 0x5c, 0x2f,
    0xa7, 0x1c, 0xc9, 0x09, 0x69, 0x9a, 0x83, 0xcf,
    0x29, 0x39, 0xb9, 0xe9, 0x4c, 0xff, 0x43, 0xab,
  };

  /** Inverse mapping of RC2Version code to effective bits. */
  private static final int[] VERSION_TO_EFFECTIVE_BITS = new int[256];


  /**
   * Class initializer.
   */
  static {
    for (int i = 0; i < EFFECTIVE_BITS_TO_VERSION.length; i++) {
      VERSION_TO_EFFECTIVE_BITS[EFFECTIVE_BITS_TO_VERSION[i]] = i;
    }
  }

  /** Sets the effective key size in bits. */
  private int effectiveKeyBits = -1;


  /**
   * Creates a default RC2 symmetric encryption algorithm using CBC mode and
   * PKCS5 padding.
   */
  public RC2()
  {
    this(DEFAULT_MODE, DEFAULT_PADDING);
  }


  /**
   * Creates a default RC2 symmetric encryption algorithm using the given mode
   * and padding style.
   *
   * @param  mode  Cipher mode name.
   * @param  padding  Cipher padding style name.
   */
  public RC2(final String mode, final String padding)
  {
    super(ALGORITHM, mode, padding);
  }


  /**
   * Gets the number of effective bits for a given RC2Version code.
   *
   * @param  version  RC2Version code.
   *
   * @return  Number of effective bits for given version.
   */
  public static int getEffectiveBits(final int version)
  {
    if (version >= 256) {
      return version;
    } else {
      return VERSION_TO_EFFECTIVE_BITS[version];
    }
  }


  /**
   * Gets the RC2Version code for a given effective bits value.
   *
   * @param  effectiveBits  Effective bits corresponding to a particular
   * RC2Version encoded value.
   *
   * @return  RC2Version code for given effective bits.
   */
  public static int getVersion(final int effectiveBits)
  {
    if (effectiveBits >= 256) {
      return effectiveBits;
    } else {
      return EFFECTIVE_BITS_TO_VERSION[effectiveBits];
    }
  }


  /**
   * Gets the effective key size in bits. This is a parameter specific to the
   * RC2 cipher algorithm.
   *
   * @return  Effective key size in bits.
   */
  public int getEffectiveKeyBits()
  {
    return effectiveKeyBits;
  }


  /**
   * Sets the effective key size in bits. This is a parameter specific to the
   * RC2 cipher algorithm.
   *
   * @param  numBits  Effective key size in bits; MUST be positive integer.
   */
  public void setEffectiveKeyBits(final int numBits)
  {
    if (numBits < 1) {
      throw new IllegalArgumentException(
        "EffectiveKeyBits must be positive integer.");
    }
    this.effectiveKeyBits = numBits;
  }


  /** {@inheritDoc} */
  @Override
  protected AlgorithmParameterSpec getAlgorithmParameterSpec()
  {
    final AlgorithmParameterSpec spec;
    if (paramSpec != null) {
      spec = paramSpec;
    } else {
      // Use the number of bits in the key as effective bits
      // if it has not been explicitly set
      final int effective = effectiveKeyBits < 0
        ? this.key.getEncoded().length * 8 : effectiveKeyBits;
      if (iv != null) {
        spec = new RC2ParameterSpec(effective, iv);
      } else {
        spec = new RC2ParameterSpec(effective);
      }
    }
    return spec;
  }
}