// Transform an input block into an output block.
public static int TransformBlock(CryptoAPITransform transform,
byte[] inputBuffer, int inputOffset,
int inputCount, byte[] outputBuffer,
int outputOffset)
{
int blockSize = transform.blockSize;
byte[] iv = transform.iv;
IntPtr state = transform.state;
int offset = outputOffset;
int index;
// Process all of the blocks in the input.
while (inputCount >= blockSize)
{
// XOR the plaintext with the IV.
for (index = blockSize - 1; index >= 0; --index)
{
iv[index] ^= inputBuffer[inputOffset + index];
}
// Encrypt the IV to get the ciphertext and the next IV.
CryptoMethods.Encrypt(state, iv, 0, iv, 0);
Array.Copy(iv, 0, outputBuffer, offset, blockSize);
// Advance to the next block.
inputOffset += blockSize;
inputCount -= blockSize;
offset += blockSize;
}
// Finished.
return(offset - outputOffset);
}
// Transform an input block into an output block.
public static int TransformBlock(CryptoAPITransform transform,
byte[] inputBuffer, int inputOffset,
int inputCount, byte[] outputBuffer,
int outputOffset)
{
int blockSize = transform.blockSize;
byte[] iv = transform.iv;
IntPtr state = transform.state;
int offset = outputOffset;
byte[] tempBuffer = transform.tempBuffer;
int tempSize = transform.tempSize;
int index;
// Process all of the data in the input. We need to keep
// the last two blocks for the finalization process.
while (inputCount >= blockSize)
{
// If the temporary buffer is full, then flush a block
// through the cipher in CBC mode.
if (tempSize > blockSize)
{
// XOR the plaintext with the IV.
for (index = blockSize - 1; index >= 0; --index)
{
iv[index] ^= tempBuffer[index];
}
// Encrypt the IV to get the ciphertext and the next IV.
CryptoMethods.Encrypt(state, iv, 0, iv, 0);
Array.Copy(iv, 0, outputBuffer, offset, blockSize);
// Advance to the next output block.
offset += blockSize;
// Shift the second block down to the first position.
Array.Copy(tempBuffer, blockSize,
tempBuffer, 0, blockSize);
tempSize -= blockSize;
}
// Copy the next block into the temporary buffer.
Array.Copy(inputBuffer, inputOffset,
tempBuffer, tempSize, blockSize);
inputOffset += blockSize;
inputCount -= blockSize;
tempSize += blockSize;
}
transform.tempSize = tempSize;
// Finished.
return(offset - outputOffset);
}
// Transform an input block into an output block.
public static int TransformBlock(CryptoAPITransform transform,
byte[] inputBuffer, int inputOffset,
int inputCount, byte[] outputBuffer,
int outputOffset)
{
int blockSize = transform.blockSize;
int feedbackSize = transform.feedbackBlockSize;
byte[] iv = transform.iv;
IntPtr state = transform.state;
int offset = outputOffset;
byte[] tempBuffer = transform.tempBuffer;
int tempSize = transform.tempSize;
// Process all of the bytes in the input.
while (inputCount > 0)
{
// Encrypt the queue if we need more keystream data.
if (tempSize >= feedbackSize)
{
CryptoMethods.Encrypt(state, tempBuffer,
feedbackSize, tempBuffer, 0);
tempSize = 0;
}
// XOR the plaintext byte with the next keystream byte.
outputBuffer[offset++] =
(byte)(tempBuffer[tempSize] ^
inputBuffer[inputOffset++]);
--inputCount;
// Feed the keystream byte back into the queue.
tempBuffer[tempSize + blockSize] = tempBuffer[tempSize];
++tempSize;
}
transform.tempSize = tempSize;
// Finished.
return(offset - outputOffset);
}
// Transform an input block into an output block.
public static int TransformBlock(CryptoAPITransform transform,
byte[] inputBuffer, int inputOffset,
int inputCount, byte[] outputBuffer,
int outputOffset)
{
int blockSize = transform.blockSize;
IntPtr state = transform.state;
int offset = outputOffset;
// Process all of the blocks in the input.
while (inputCount >= blockSize)
{
CryptoMethods.Encrypt(state, inputBuffer, inputOffset,
outputBuffer, offset);
inputOffset += blockSize;
inputCount -= blockSize;
offset += blockSize;
}
// Finished.
return(offset - outputOffset);
}
// Transform the final input block.
public static byte[] TransformFinalBlock(CryptoAPITransform transform,
byte[] inputBuffer,
int inputOffset,
int inputCount)
{
int blockSize = transform.blockSize;
byte[] iv = transform.iv;
IntPtr state = transform.state;
int offset;
byte[] tempBuffer = transform.tempBuffer;
byte[] outputBuffer;
int tempSize;
int index;
// Allocate the output buffer.
outputBuffer = new byte [inputCount + transform.tempSize];
// Process as many full blocks as possible.
index = inputCount - (inputCount % blockSize);
offset = TransformBlock(transform, inputBuffer,
inputOffset, index,
outputBuffer, 0);
inputOffset += index;
inputCount -= index;
// Flush the first block if we need the extra space.
tempSize = transform.tempSize;
if (tempSize > blockSize && inputCount > 0)
{
// Decrypt the ciphertext block and XOR with the IV.
CryptoMethods.Decrypt(state, tempBuffer, blockSize,
tempBuffer, 0);
for (index = blockSize - 1; index >= 0; --index)
{
tempBuffer[index] ^= iv[index];
}
// Copy the original ciphertext to the IV.
Array.Copy(tempBuffer, blockSize, iv, 0, blockSize);
// Copy the plaintext into place.
Array.Copy(tempBuffer, 0, outputBuffer,
offset, blockSize);
// Advance to the next output block.
offset += blockSize;
// Shift the second block down to the first position.
Array.Copy(tempBuffer, blockSize * 2,
tempBuffer, blockSize, blockSize);
tempSize -= blockSize;
}
// Copy the remainder of the data into the temporary buffer.
Array.Copy(inputBuffer, inputOffset,
tempBuffer, tempSize + blockSize, inputCount);
tempSize += inputCount;
// "Applied Cryptography" describes Cipher Text Stealing
// as taking two blocks to generate the short end-point.
// If we less than one block, then use CFB instead.
if (tempSize < blockSize)
{
// Decrypt the single block in CFB mode.
CryptoMethods.Encrypt(transform.state2, iv, 0, iv, 0);
for (index = 0; index < tempSize; ++index)
{
outputBuffer[offset + index] =
(byte)(iv[index] ^ tempBuffer[index + blockSize]);
}
}
else
{
// Decrypt the second last ciphertext block.
CryptoMethods.Decrypt(state, tempBuffer, blockSize,
tempBuffer, blockSize);
// Rebuild the ciphertext for the last block.
for (index = inputCount; index < blockSize; ++index)
{
tempBuffer[blockSize * 2 + index] =
tempBuffer[blockSize + index];
}
// Get the last plaintext block from the second
// last ciphertext block.
for (index = inputCount - 1; index >= 0; --index)
{
outputBuffer[offset + blockSize + index] =
(byte)(tempBuffer[blockSize + index] ^
tempBuffer[blockSize * 2 + index]);
}
// Decrypt the last ciphertext block that we rebuilt.
CryptoMethods.Decrypt(state, tempBuffer, blockSize * 2,
tempBuffer, 0);
// XOR the block with the IV to get the second
// last plaintext block.
for (index = blockSize - 1; index >= 0; --index)
{
outputBuffer[offset + index] =
(byte)(iv[index] ^ tempBuffer[index]);
}
}
// Finished.
return(outputBuffer);
}
// Transform the final input block.
public static byte[] TransformFinalBlock(CryptoAPITransform transform,
byte[] inputBuffer,
int inputOffset,
int inputCount)
{
int blockSize = transform.blockSize;
IntPtr state = transform.state;
int offset = 0;
int size, index, pad;
byte[] outputBuffer;
// Allocate space for the final block.
if (transform.padding == PaddingMode.PKCS7)
{
size = inputCount + blockSize - (inputCount % blockSize);
}
else
{
size = inputCount;
if ((size % blockSize) != 0)
{
size += blockSize - (inputCount % blockSize);
}
}
outputBuffer = new byte [size];
// Process full blocks in the input.
while (inputCount >= blockSize)
{
CryptoMethods.Encrypt(state, inputBuffer, inputOffset,
outputBuffer, offset);
inputOffset += blockSize;
inputCount -= blockSize;
offset += blockSize;
}
// Format and encrypt the final partial block.
if (transform.padding == PaddingMode.PKCS7)
{
// Pad the block according to PKCS #7.
for (index = 0; index < inputCount; ++index)
{
outputBuffer[offset + index] =
inputBuffer[inputOffset + index];
}
pad = blockSize - (inputCount % blockSize);
while (index < blockSize)
{
outputBuffer[offset + index] = (byte)pad;
++index;
}
// Encrypt the block.
CryptoMethods.Encrypt(state, outputBuffer,
offset + index - blockSize,
outputBuffer,
offset + index - blockSize);
}
else if (inputCount > 0)
{
// Pad the block with zero bytes.
for (index = 0; index < inputCount; ++index)
{
outputBuffer[offset + index] =
inputBuffer[inputOffset + index];
}
while (index < blockSize)
{
outputBuffer[offset + index] = (byte)0x00;
++index;
}
// Encrypt the block.
CryptoMethods.Encrypt(state, outputBuffer,
offset + index - blockSize,
outputBuffer,
offset + index - blockSize);
}
// Finished.
return(outputBuffer);
}
// Transform the final input block.
public static byte[] TransformFinalBlock(CryptoAPITransform transform,
byte[] inputBuffer,
int inputOffset,
int inputCount)
{
int blockSize = transform.blockSize;
byte[] iv = transform.iv;
IntPtr state = transform.state;
int offset = 0;
int size, pad, index;
byte[] outputBuffer;
// Allocate space for the final block.
if (transform.padding == PaddingMode.PKCS7)
{
size = inputCount + blockSize - (inputCount % blockSize);
}
else
{
size = inputCount;
if ((size % blockSize) != 0)
{
size += blockSize - (inputCount % blockSize);
}
}
outputBuffer = new byte [size];
// Process full blocks in the input.
while (inputCount >= blockSize)
{
// XOR the plaintext with the IV.
for (index = blockSize - 1; index >= 0; --index)
{
iv[index] ^= inputBuffer[inputOffset + index];
}
// Encrypt the IV to get the ciphertext and the next IV.
CryptoMethods.Encrypt(state, iv, 0, iv, 0);
Array.Copy(iv, 0, outputBuffer, offset, blockSize);
// Advance to the next block.
inputOffset += blockSize;
inputCount -= blockSize;
offset += blockSize;
}
// Format and encrypt the final partial block.
if (transform.padding == PaddingMode.PKCS7)
{
// Pad the block according to PKCS #7 and XOR with the IV.
for (index = 0; index < inputCount; ++index)
{
iv[index] ^= inputBuffer[inputOffset + index];
}
pad = blockSize - (inputCount % blockSize);
while (index < blockSize)
{
iv[index] ^= (byte)pad;
++index;
}
// Encrypt the IV to get the ciphertext and the next IV.
CryptoMethods.Encrypt(state, iv, 0, iv, 0);
Array.Copy(iv, 0, outputBuffer, offset, blockSize);
}
else if (inputCount > 0)
{
// Pad the block with zero bytes and XOR with the IV.
// The zero padding is implicit.
for (index = 0; index < inputCount; ++index)
{
iv[index] ^= inputBuffer[inputOffset + index];
}
// Encrypt the IV to get the ciphertext and the next IV.
CryptoMethods.Encrypt(state, iv, 0, iv, 0);
Array.Copy(iv, 0, outputBuffer, offset, blockSize);
}
// Finished.
return(outputBuffer);
}