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using System;
namespace Org.BouncyCastle.Crypto.Parameters
{
public class DesParameters
: KeyParameter
{
public DesParameters(
byte[] key)
: base(key)
{
if (IsWeakKey(key))
throw new ArgumentException("attempt to create weak DES key");
}
public DesParameters(
byte[] key,
int keyOff,
int keyLen)
: base(key, keyOff, keyLen)
{
if (IsWeakKey(key, keyOff))
throw new ArgumentException("attempt to create weak DES key");
}
/*
* DES Key Length in bytes.
*/
public const int DesKeyLength = 8;
/*
* Table of weak and semi-weak keys taken from Schneier pp281
*/
private const int N_DES_WEAK_KEYS = 16;
private static readonly 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.
* </p>
* @return true if the given DES key material is weak or semi-weak,
* false otherwise.
*/
public static bool IsWeakKey(
byte[] key,
int offset)
{
if (key.Length - offset < DesKeyLength)
throw new ArgumentException("key material too short.");
//nextkey:
for (int i = 0; i < N_DES_WEAK_KEYS; i++)
{
bool unmatch = false;
for (int j = 0; j < DesKeyLength; j++)
{
if (key[j + offset] != DES_weak_keys[i * DesKeyLength + j])
{
//continue nextkey;
unmatch = true;
break;
}
}
if (!unmatch)
{
return true;
}
}
return false;
}
public static bool IsWeakKey(
byte[] key)
{
return IsWeakKey(key, 0);
}
public static byte SetOddParity(byte b)
{
uint parity = b ^ 1U;
parity ^= (parity >> 4);
parity ^= (parity >> 2);
parity ^= (parity >> 1);
parity &= 1U;
return (byte)(b ^ parity);
}
/**
* 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++)
{
bytes[i] = SetOddParity(bytes[i]);
}
}
public static void SetOddParity(byte[] bytes, int off, int len)
{
for (int i = 0; i < len; i++)
{
bytes[off + i] = SetOddParity(bytes[off + i]);
}
}
}
}
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