org.testifyproject.bouncycastle.crypto.params.DESParameters Maven / Gradle / Ivy
package org.testifyproject.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.
*
* @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));
}
}
}