openpgpcfbblockcipher.java

java 文件下载器。可自定义

// Decompiled by Jad v1.5.8e2. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://kpdus.tripod.com/jad.html
// Decompiler options: packimports(3) fieldsfirst ansi space 
// Source File Name:   OpenPGPCFBBlockCipher.java

package org.bouncycastle.crypto.modes;

import org.bouncycastle.crypto.*;

public class OpenPGPCFBBlockCipher
	implements BlockCipher
{

	private byte IV[];
	private byte FR[];
	private byte FRE[];
	private byte tmp[];
	private BlockCipher cipher;
	private int count;
	private int blockSize;
	private boolean forEncryption;

	public OpenPGPCFBBlockCipher(BlockCipher cipher)
	{
		this.cipher = cipher;
		blockSize = cipher.getBlockSize();
		IV = new byte[blockSize];
		FR = new byte[blockSize];
		FRE = new byte[blockSize];
		tmp = new byte[blockSize];
	}

	public BlockCipher getUnderlyingCipher()
	{
		return cipher;
	}

	public String getAlgorithmName()
	{
		return (new StringBuilder()).append(cipher.getAlgorithmName()).append("/OpenPGPCFB").toString();
	}

	public int getBlockSize()
	{
		return cipher.getBlockSize();
	}

	public int processBlock(byte in[], int inOff, byte out[], int outOff)
		throws DataLengthException, IllegalStateException
	{
		return forEncryption ? encryptBlock(in, inOff, out, outOff) : decryptBlock(in, inOff, out, outOff);
	}

	public void reset()
	{
		count = 0;
		for (int i = 0; i != FR.length; i++)
			FR[i] = IV[i];

		cipher.reset();
	}

	public void init(boolean forEncryption, CipherParameters params)
		throws IllegalArgumentException
	{
		this.forEncryption = forEncryption;
		reset();
		cipher.init(true, params);
	}

	private byte encryptByte(byte data, int blockOff)
	{
		return (byte)(FRE[blockOff] ^ data);
	}

	private int encryptBlock(byte in[], int inOff, byte out[], int outOff)
		throws DataLengthException, IllegalStateException
	{
		if (inOff + blockSize > in.length)
			throw new DataLengthException("input buffer too short");
		if (outOff + blockSize > out.length)
			throw new DataLengthException("output buffer too short");
		if (count > blockSize)
		{
			FR[blockSize - 2] = out[outOff] = encryptByte(in[inOff], blockSize - 2);
			FR[blockSize - 1] = out[outOff + 1] = encryptByte(in[inOff + 1], blockSize - 1);
			cipher.processBlock(FR, 0, FRE, 0);
			for (int n = 2; n < blockSize; n++)
				out[outOff + n] = encryptByte(in[inOff + n], n - 2);

			System.arraycopy(out, outOff + 2, FR, 0, blockSize - 2);
		} else
		if (count == 0)
		{
			cipher.processBlock(FR, 0, FRE, 0);
			for (int n = 0; n < blockSize; n++)
				out[outOff + n] = encryptByte(in[inOff + n], n);

			System.arraycopy(out, outOff, FR, 0, blockSize);
			count += blockSize;
		} else
		if (count == blockSize)
		{
			cipher.processBlock(FR, 0, FRE, 0);
			out[outOff] = encryptByte(in[inOff], 0);
			out[outOff + 1] = encryptByte(in[inOff + 1], 1);
			System.arraycopy(FR, 2, FR, 0, blockSize - 2);
			System.arraycopy(out, outOff, FR, blockSize - 2, 2);
			cipher.processBlock(FR, 0, FRE, 0);
			for (int n = 2; n < blockSize; n++)
				out[outOff + n] = encryptByte(in[inOff + n], n - 2);

			System.arraycopy(out, outOff + 2, FR, 0, blockSize - 2);
			count += blockSize;
		}
		return blockSize;
	}

	private int decryptBlock(byte in[], int inOff, byte out[], int outOff)
		throws DataLengthException, IllegalStateException
	{
		if (inOff + blockSize > in.length)
			throw new DataLengthException("input buffer too short");
		if (outOff + blockSize > out.length)
			throw new DataLengthException("output buffer too short");
		if (count > blockSize)
		{
			System.arraycopy(in, inOff, tmp, 0, blockSize);
			out[outOff + 0] = encryptByte(tmp[0], blockSize - 2);
			out[outOff + 1] = encryptByte(tmp[1], blockSize - 1);
			System.arraycopy(tmp, 0, FR, blockSize - 2, 2);
			cipher.processBlock(FR, 0, FRE, 0);
			for (int n = 2; n < blockSize; n++)
				out[outOff + n] = encryptByte(tmp[n], n - 2);

			System.arraycopy(tmp, 2, FR, 0, blockSize - 2);
		} else
		if (count == 0)
		{
			cipher.processBlock(FR, 0, FRE, 0);
			for (int n = 0; n < blockSize; n++)
			{
				FR[n] = in[inOff + n];
				out[n] = encryptByte(in[inOff + n], n);
			}

			count += blockSize;
		} else
		if (count == blockSize)
		{
			System.arraycopy(in, inOff, tmp, 0, blockSize);
			cipher.processBlock(FR, 0, FRE, 0);
			out[outOff + 0] = encryptByte(tmp[0], 0);
			out[outOff + 1] = encryptByte(tmp[1], 1);
			System.arraycopy(FR, 2, FR, 0, blockSize - 2);
			FR[blockSize - 2] = tmp[0];
			FR[blockSize - 1] = tmp[1];
			cipher.processBlock(FR, 0, FRE, 0);
			for (int n = 2; n < blockSize; n++)
			{
				FR[n - 2] = in[inOff + n];
				out[outOff + n] = encryptByte(in[inOff + n], n - 2);
			}

			count += blockSize;
		}
		return blockSize;
	}
}