package org.bouncycastle.crypto.params;
   
   /*-
    * ╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲
    * SNMP Java Client
    * ჻჻჻჻჻჻
    * Copyright 2023 Sentry Software, Westhawk
    * ჻჻჻჻჻჻
    * This program is free software: you can redistribute it and/or modify
   * it under the terms of the GNU Lesser General Public License as
   * published by the Free Software Foundation, either version 3 of the
   * License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Lesser Public License for more details.
   *
   * You should have received a copy of the GNU General Lesser Public
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-3.0.html>.
   * ╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱
   */
  
  public class DESParameters
      extends KeyParameter
  {
      public DESParameters(
          byte[]  key)
      {
          super(key);
  
          if (isWeakKey(key, 0))
          {
              throw new IllegalArgumentException("attempt to create weak DES key");
          }
      }
  
      /*
       * DES Key length in bytes.
       */
      static public final int DES_KEY_LENGTH = 8;
  
      /*
       * Table of weak and semi-weak keys taken from Schneier pp281
       */
      static private final int N_DES_WEAK_KEYS = 16;
  
      static private byte[] DES_weak_keys =
      {
          /* weak keys */
          (byte)0x01,(byte)0x01,(byte)0x01,(byte)0x01, (byte)0x01,(byte)0x01,(byte)0x01,(byte)0x01,
          (byte)0x1f,(byte)0x1f,(byte)0x1f,(byte)0x1f, (byte)0x0e,(byte)0x0e,(byte)0x0e,(byte)0x0e,
          (byte)0xe0,(byte)0xe0,(byte)0xe0,(byte)0xe0, (byte)0xf1,(byte)0xf1,(byte)0xf1,(byte)0xf1,
          (byte)0xfe,(byte)0xfe,(byte)0xfe,(byte)0xfe, (byte)0xfe,(byte)0xfe,(byte)0xfe,(byte)0xfe,
  
          /* semi-weak keys */
          (byte)0x01,(byte)0xfe,(byte)0x01,(byte)0xfe, (byte)0x01,(byte)0xfe,(byte)0x01,(byte)0xfe,
          (byte)0x1f,(byte)0xe0,(byte)0x1f,(byte)0xe0, (byte)0x0e,(byte)0xf1,(byte)0x0e,(byte)0xf1,
          (byte)0x01,(byte)0xe0,(byte)0x01,(byte)0xe0, (byte)0x01,(byte)0xf1,(byte)0x01,(byte)0xf1,
          (byte)0x1f,(byte)0xfe,(byte)0x1f,(byte)0xfe, (byte)0x0e,(byte)0xfe,(byte)0x0e,(byte)0xfe,
          (byte)0x01,(byte)0x1f,(byte)0x01,(byte)0x1f, (byte)0x01,(byte)0x0e,(byte)0x01,(byte)0x0e,
          (byte)0xe0,(byte)0xfe,(byte)0xe0,(byte)0xfe, (byte)0xf1,(byte)0xfe,(byte)0xf1,(byte)0xfe,
          (byte)0xfe,(byte)0x01,(byte)0xfe,(byte)0x01, (byte)0xfe,(byte)0x01,(byte)0xfe,(byte)0x01,
          (byte)0xe0,(byte)0x1f,(byte)0xe0,(byte)0x1f, (byte)0xf1,(byte)0x0e,(byte)0xf1,(byte)0x0e,
          (byte)0xe0,(byte)0x01,(byte)0xe0,(byte)0x01, (byte)0xf1,(byte)0x01,(byte)0xf1,(byte)0x01,
          (byte)0xfe,(byte)0x1f,(byte)0xfe,(byte)0x1f, (byte)0xfe,(byte)0x0e,(byte)0xfe,(byte)0x0e,
          (byte)0x1f,(byte)0x01,(byte)0x1f,(byte)0x01, (byte)0x0e,(byte)0x01,(byte)0x0e,(byte)0x01,
          (byte)0xfe,(byte)0xe0,(byte)0xfe,(byte)0xe0, (byte)0xfe,(byte)0xf1,(byte)0xfe,(byte)0xf1
      };
  
      /**
       * DES has 16 weak keys.  This method will check
       * if the given DES key material is weak or semi-weak.
       * Key material that is too short is regarded as weak.
       * <p>
       * See <a href="http://www.counterpane.com/applied.html">"Applied
       * Cryptography"</a> by Bruce Schneier for more information.
       *
       * @return true if the given DES key material is weak or semi-weak,
       *     false otherwise.
       */
      public static boolean isWeakKey(
          byte[] key,
          int offset)
      {
          if (key.length - offset < DES_KEY_LENGTH)
          {
              throw new IllegalArgumentException("key material too short.");
          }
  
          nextkey: for (int i = 0; i < N_DES_WEAK_KEYS; i++)
          {
              for (int j = 0; j < DES_KEY_LENGTH; j++)
              {
                  if (key[j + offset] != DES_weak_keys[i * DES_KEY_LENGTH + j])
                  {
                      continue nextkey;
                  }
             }
 
             return true;
         }
         return false;
     }
 
     /**
      * DES Keys use the LSB as the odd parity bit.  This can
      * be used to check for corrupt keys.
      *
      * @param bytes the byte array to set the parity on.
      */
     public static void setOddParity(
         byte[] bytes)
     {
         for (int i = 0; i < bytes.length; i++)
         {
             int b = bytes[i];
             bytes[i] = (byte)((b & 0xfe) |
                             ((((b >> 1) ^
                             (b >> 2) ^
                             (b >> 3) ^
                             (b >> 4) ^
                             (b >> 5) ^
                             (b >> 6) ^
                             (b >> 7)) ^ 0x01) & 0x01));
         }
     }
 }