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using System;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Crypto.Utilities;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Engines
{
/**
* An XTEA engine.
*/
public class XteaEngine
: IBlockCipher
{
private const int
rounds = 32,
block_size = 8,
// key_size = 16,
delta = unchecked((int) 0x9E3779B9);
/*
* the expanded key array of 4 subkeys
*/
private uint[] _S = new uint[4],
_sum0 = new uint[32],
_sum1 = new uint[32];
private bool _initialised, _forEncryption;
/**
* Create an instance of the TEA encryption algorithm
* and set some defaults
*/
public XteaEngine()
{
_initialised = false;
}
public virtual string AlgorithmName
{
get { return "XTEA"; }
}
public virtual bool IsPartialBlockOkay
{
get { return false; }
}
public virtual int GetBlockSize()
{
return block_size;
}
/**
* initialise
*
* @param forEncryption whether or not we are for encryption.
* @param params the parameters required to set up the cipher.
* @exception ArgumentException if the params argument is
* inappropriate.
*/
public virtual void Init(
bool forEncryption,
ICipherParameters parameters)
{
if (!(parameters is KeyParameter))
{
throw new ArgumentException("invalid parameter passed to TEA init - "
+ Platform.GetTypeName(parameters));
}
_forEncryption = forEncryption;
_initialised = true;
KeyParameter p = (KeyParameter) parameters;
setKey(p.GetKey());
}
public virtual int ProcessBlock(
byte[] inBytes,
int inOff,
byte[] outBytes,
int outOff)
{
if (!_initialised)
throw new InvalidOperationException(AlgorithmName + " not initialised");
Check.DataLength(inBytes, inOff, block_size, "input buffer too short");
Check.OutputLength(outBytes, outOff, block_size, "output buffer too short");
return _forEncryption
? encryptBlock(inBytes, inOff, outBytes, outOff)
: decryptBlock(inBytes, inOff, outBytes, outOff);
}
public virtual void Reset()
{
}
/**
* Re-key the cipher.
*
* @param key the key to be used
*/
private void setKey(
byte[] key)
{
int i, j;
for (i = j = 0; i < 4; i++,j+=4)
{
_S[i] = Pack.BE_To_UInt32(key, j);
}
for (i = j = 0; i < rounds; i++)
{
_sum0[i] = ((uint)j + _S[j & 3]);
j += delta;
_sum1[i] = ((uint)j + _S[j >> 11 & 3]);
}
}
private int encryptBlock(
byte[] inBytes,
int inOff,
byte[] outBytes,
int outOff)
{
// Pack bytes into integers
uint v0 = Pack.BE_To_UInt32(inBytes, inOff);
uint v1 = Pack.BE_To_UInt32(inBytes, inOff + 4);
for (int i = 0; i < rounds; i++)
{
v0 += ((v1 << 4 ^ v1 >> 5) + v1) ^ _sum0[i];
v1 += ((v0 << 4 ^ v0 >> 5) + v0) ^ _sum1[i];
}
Pack.UInt32_To_BE(v0, outBytes, outOff);
Pack.UInt32_To_BE(v1, outBytes, outOff + 4);
return block_size;
}
private int decryptBlock(
byte[] inBytes,
int inOff,
byte[] outBytes,
int outOff)
{
// Pack bytes into integers
uint v0 = Pack.BE_To_UInt32(inBytes, inOff);
uint v1 = Pack.BE_To_UInt32(inBytes, inOff + 4);
for (int i = rounds-1; i >= 0; i--)
{
v1 -= ((v0 << 4 ^ v0 >> 5) + v0) ^ _sum1[i];
v0 -= ((v1 << 4 ^ v1 >> 5) + v1) ^ _sum0[i];
}
Pack.UInt32_To_BE(v0, outBytes, outOff);
Pack.UInt32_To_BE(v1, outBytes, outOff + 4);
return block_size;
}
}
}
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