package org.bouncycastle.crypto.params;

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.

See "Applied Cryptography" by Bruce Schneier for more information.

Returns:true if the given DES key material is weak or semi-weak, false otherwise.
/** * 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.
Params:
  • bytes – the byte array to set the parity on.
/** * 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)); } } }