1 package org.bouncycastle.crypto.params; 2 3 public class DESParameters 4 extends KeyParameter 5 { 6 public DESParameters( 7 byte[] key) 8 { 9 super(key); 10 11 if (isWeakKey(key, 0)) 12 { 13 throw new IllegalArgumentException("attempt to create weak DES key"); 14 } 15 } 16 17 /* 18 * DES Key length in bytes. 19 */ 20 static public final int DES_KEY_LENGTH = 8; 21 22 /* 23 * Table of weak and semi-weak keys taken from Schneier pp281 24 */ 25 static private final int N_DES_WEAK_KEYS = 16; 26 27 static private byte[] DES_weak_keys = 28 { 29 /* weak keys */ 30 (byte)0x01,(byte)0x01,(byte)0x01,(byte)0x01, (byte)0x01,(byte)0x01,(byte)0x01,(byte)0x01, 31 (byte)0x1f,(byte)0x1f,(byte)0x1f,(byte)0x1f, (byte)0x0e,(byte)0x0e,(byte)0x0e,(byte)0x0e, 32 (byte)0xe0,(byte)0xe0,(byte)0xe0,(byte)0xe0, (byte)0xf1,(byte)0xf1,(byte)0xf1,(byte)0xf1, 33 (byte)0xfe,(byte)0xfe,(byte)0xfe,(byte)0xfe, (byte)0xfe,(byte)0xfe,(byte)0xfe,(byte)0xfe, 34 35 /* semi-weak keys */ 36 (byte)0x01,(byte)0xfe,(byte)0x01,(byte)0xfe, (byte)0x01,(byte)0xfe,(byte)0x01,(byte)0xfe, 37 (byte)0x1f,(byte)0xe0,(byte)0x1f,(byte)0xe0, (byte)0x0e,(byte)0xf1,(byte)0x0e,(byte)0xf1, 38 (byte)0x01,(byte)0xe0,(byte)0x01,(byte)0xe0, (byte)0x01,(byte)0xf1,(byte)0x01,(byte)0xf1, 39 (byte)0x1f,(byte)0xfe,(byte)0x1f,(byte)0xfe, (byte)0x0e,(byte)0xfe,(byte)0x0e,(byte)0xfe, 40 (byte)0x01,(byte)0x1f,(byte)0x01,(byte)0x1f, (byte)0x01,(byte)0x0e,(byte)0x01,(byte)0x0e, 41 (byte)0xe0,(byte)0xfe,(byte)0xe0,(byte)0xfe, (byte)0xf1,(byte)0xfe,(byte)0xf1,(byte)0xfe, 42 (byte)0xfe,(byte)0x01,(byte)0xfe,(byte)0x01, (byte)0xfe,(byte)0x01,(byte)0xfe,(byte)0x01, 43 (byte)0xe0,(byte)0x1f,(byte)0xe0,(byte)0x1f, (byte)0xf1,(byte)0x0e,(byte)0xf1,(byte)0x0e, 44 (byte)0xe0,(byte)0x01,(byte)0xe0,(byte)0x01, (byte)0xf1,(byte)0x01,(byte)0xf1,(byte)0x01, 45 (byte)0xfe,(byte)0x1f,(byte)0xfe,(byte)0x1f, (byte)0xfe,(byte)0x0e,(byte)0xfe,(byte)0x0e, 46 (byte)0x1f,(byte)0x01,(byte)0x1f,(byte)0x01, (byte)0x0e,(byte)0x01,(byte)0x0e,(byte)0x01, 47 (byte)0xfe,(byte)0xe0,(byte)0xfe,(byte)0xe0, (byte)0xfe,(byte)0xf1,(byte)0xfe,(byte)0xf1 48 }; 49 50 /** 51 * DES has 16 weak keys. This method will check 52 * if the given DES key material is weak or semi-weak. 53 * Key material that is too short is regarded as weak. 54 * <p> 55 * See <a href="http://www.counterpane.com/applied.html">"Applied 56 * Cryptography"</a> by Bruce Schneier for more information. 57 * 58 * @return true if the given DES key material is weak or semi-weak, 59 * false otherwise. 60 */ 61 public static boolean isWeakKey( 62 byte[] key, 63 int offset) 64 { 65 if (key.length - offset < DES_KEY_LENGTH) 66 { 67 throw new IllegalArgumentException("key material too short."); 68 } 69 70 nextkey: for (int i = 0; i < N_DES_WEAK_KEYS; i++) 71 { 72 for (int j = 0; j < DES_KEY_LENGTH; j++) 73 { 74 if (key[j + offset] != DES_weak_keys[i * DES_KEY_LENGTH + j]) 75 { 76 continue nextkey; 77 } 78 } 79 80 return true; 81 } 82 return false; 83 } 84 85 /** 86 * DES Keys use the LSB as the odd parity bit. This can 87 * be used to check for corrupt keys. 88 * 89 * @param bytes the byte array to set the parity on. 90 */ 91 public static void setOddParity( 92 byte[] bytes) 93 { 94 for (int i = 0; i < bytes.length; i++) 95 { 96 int b = bytes[i]; 97 bytes[i] = (byte)((b & 0xfe) | 98 ((((b >> 1) ^ 99 (b >> 2) ^ 100 (b >> 3) ^ 101 (b >> 4) ^ 102 (b >> 5) ^ 103 (b >> 6) ^ 104 (b >> 7)) ^ 0x01) & 0x01)); 105 } 106 } 107 } 108
