OpenPgpCfbBlockCipher
using Org.BouncyCastle.Crypto.Parameters;
using System;
namespace Org.BouncyCastle.Crypto.Modes
{
public class OpenPgpCfbBlockCipher : IBlockCipherMode, IBlockCipher
{
private byte[] IV;
private byte[] FR;
private byte[] FRE;
private readonly IBlockCipher cipher;
private readonly int blockSize;
private int count;
private bool forEncryption;
public IBlockCipher UnderlyingCipher => cipher;
public string AlgorithmName => cipher.AlgorithmName + "/OpenPGPCFB";
public bool IsPartialBlockOkay => true;
public OpenPgpCfbBlockCipher(IBlockCipher cipher)
{
this.cipher = cipher;
blockSize = cipher.GetBlockSize();
IV = new byte[blockSize];
FR = new byte[blockSize];
FRE = new byte[blockSize];
}
public int GetBlockSize()
{
return cipher.GetBlockSize();
}
public int ProcessBlock(byte[] input, int inOff, byte[] output, int outOff)
{
if (!forEncryption)
return DecryptBlock(input, inOff, output, outOff);
return EncryptBlock(input, inOff, output, outOff);
}
public void Reset()
{
count = 0;
Array.Copy(IV, 0, FR, 0, FR.Length);
}
public void Init(bool forEncryption, ICipherParameters parameters)
{
this.forEncryption = forEncryption;
ParametersWithIV parametersWithIV = parameters as ParametersWithIV;
if (parametersWithIV != null) {
byte[] iV = parametersWithIV.GetIV();
if (iV.Length < IV.Length) {
Array.Copy(iV, 0, IV, IV.Length - iV.Length, iV.Length);
for (int i = 0; i < IV.Length - iV.Length; i++) {
IV[i] = 0;
}
} else
Array.Copy(iV, 0, IV, 0, IV.Length);
parameters = parametersWithIV.Parameters;
}
Reset();
cipher.Init(true, parameters);
}
private byte EncryptByte(byte data, int blockOff)
{
return (byte)(FRE[blockOff] ^ data);
}
private int EncryptBlock(byte[] input, int inOff, byte[] outBytes, int outOff)
{
Check.DataLength(input, inOff, blockSize, "input buffer too short");
Check.OutputLength(outBytes, outOff, blockSize, "output buffer too short");
if (count > blockSize) {
byte[] fR = FR;
int num = blockSize - 2;
byte b;
outBytes[outOff] = (b = EncryptByte(input[inOff], blockSize - 2));
fR[num] = b;
byte[] fR2 = FR;
int num2 = blockSize - 1;
outBytes[outOff + 1] = (b = EncryptByte(input[inOff + 1], blockSize - 1));
fR2[num2] = b;
cipher.ProcessBlock(FR, 0, FRE, 0);
for (int i = 2; i < blockSize; i++) {
byte[] fR3 = FR;
int num3 = i - 2;
outBytes[outOff + i] = (b = EncryptByte(input[inOff + i], i - 2));
fR3[num3] = b;
}
} else if (count == 0) {
cipher.ProcessBlock(FR, 0, FRE, 0);
for (int j = 0; j < blockSize; j++) {
byte[] fR4 = FR;
int num4 = j;
byte b;
outBytes[outOff + j] = (b = EncryptByte(input[inOff + j], j));
fR4[num4] = b;
}
count += blockSize;
} else if (count == blockSize) {
cipher.ProcessBlock(FR, 0, FRE, 0);
outBytes[outOff] = EncryptByte(input[inOff], 0);
outBytes[outOff + 1] = EncryptByte(input[inOff + 1], 1);
Array.Copy(FR, 2, FR, 0, blockSize - 2);
Array.Copy(outBytes, outOff, FR, blockSize - 2, 2);
cipher.ProcessBlock(FR, 0, FRE, 0);
for (int k = 2; k < blockSize; k++) {
byte[] fR5 = FR;
int num5 = k - 2;
byte b;
outBytes[outOff + k] = (b = EncryptByte(input[inOff + k], k - 2));
fR5[num5] = b;
}
count += blockSize;
}
return blockSize;
}
private int DecryptBlock(byte[] input, int inOff, byte[] outBytes, int outOff)
{
Check.DataLength(input, inOff, blockSize, "input buffer too short");
Check.OutputLength(outBytes, outOff, blockSize, "output buffer too short");
if (count > blockSize) {
byte b = input[inOff];
FR[blockSize - 2] = b;
outBytes[outOff] = EncryptByte(b, blockSize - 2);
b = input[inOff + 1];
FR[blockSize - 1] = b;
outBytes[outOff + 1] = EncryptByte(b, blockSize - 1);
cipher.ProcessBlock(FR, 0, FRE, 0);
for (int i = 2; i < blockSize; i++) {
b = input[inOff + i];
FR[i - 2] = b;
outBytes[outOff + i] = EncryptByte(b, i - 2);
}
} else if (count == 0) {
cipher.ProcessBlock(FR, 0, FRE, 0);
for (int j = 0; j < blockSize; j++) {
FR[j] = input[inOff + j];
outBytes[outOff + j] = EncryptByte(input[inOff + j], j);
}
count += blockSize;
} else if (count == blockSize) {
cipher.ProcessBlock(FR, 0, FRE, 0);
byte b2 = input[inOff];
byte b3 = input[inOff + 1];
outBytes[outOff] = EncryptByte(b2, 0);
outBytes[outOff + 1] = EncryptByte(b3, 1);
Array.Copy(FR, 2, FR, 0, blockSize - 2);
FR[blockSize - 2] = b2;
FR[blockSize - 1] = b3;
cipher.ProcessBlock(FR, 0, FRE, 0);
for (int k = 2; k < blockSize; k++) {
byte b4 = input[inOff + k];
FR[k - 2] = b4;
outBytes[outOff + k] = EncryptByte(b4, k - 2);
}
count += blockSize;
}
return blockSize;
}
}
}