public override SymmetricCipherResult ProcessPayload(IModeBlockCipherParameters param)
{
CheckPayloadRequirements(param.Payload);
var key = param.Key.ToBytes();
var actualBitsToProcess = param.Payload.BitLength;
param.Payload = BitString.PadToModulus(param.Payload, _engine.BlockSizeBits);
// OFB always utilizes engine in encrypt mode
var engineParam = new EngineInitParameters(BlockCipherDirections.Encrypt, key, param.UseInverseCipherMode);
_engine.Init(engineParam);
var numberOfBlocks = GetNumberOfBlocks(param.Payload.BitLength);
var outBuffer = GetOutputBuffer(param.Payload.BitLength);
if (numberOfBlocks < PARTITIONS)
{
throw new ArgumentOutOfRangeException(nameof(param.Payload), $"Ofb-I mode requires a minimum of {PARTITIONS} blocks");
}
var ivs = SetupIvs(param.Iv);
ProcessPayload(param, ivs, numberOfBlocks, outBuffer);
return(new SymmetricCipherResult(
new BitString(outBuffer).GetMostSignificantBits(actualBitsToProcess)
));
}
public void DecryptTestsCs2(string label, BitString key, BitString iv, BitString pt, BitString ct, BitString nextIv)
{
// transform the cs3 ct to cs3 again (to cancel the sample vector CS3)
var ctBytes = BitString.PadToModulus(ct, _engine.BlockSizeBits).ToBytes();
var numberOfBlocks = GetNumberOfBlocks(pt.BitLength);
var cs3Transformer = _csTransform.Get(CiphertextStealingMode.CS3);
cs3Transformer.TransformCiphertext(ctBytes, _engine, numberOfBlocks, pt.BitLength);
// apply a cs2 transform
var cs2Transformer = _csTransform.Get(CiphertextStealingMode.CS2);
cs2Transformer.TransformCiphertext(ctBytes, _engine, numberOfBlocks, pt.BitLength);
ct = new BitString(ctBytes).GetMostSignificantBits(pt.BitLength);
var param = new ModeBlockCipherParameters(
BlockCipherDirections.Decrypt,
iv,
key,
ct
);
var result = _subjectCs2.ProcessPayload(param);
Assert.AreEqual(pt.ToHex(), result.Result.ToHex(), nameof(pt));
Assert.AreEqual(nextIv.ToHex(), param.Iv.ToHex(), nameof(nextIv));
}
public byte[] HandleFinalFullPayloadBlockDecryption(BitString payload, IBlockCipherEngine engine, int numberOfBlocks, int originalPayloadBitLength)
{
// Decrypt the last full payload block (when there is more than one block)
if (numberOfBlocks > 1)
{
var originalPayloadPaddedToBlockSize = payload.PadToModulus(engine.BlockSizeBits).ToBytes();
// Decrypt the last full payload block (in this case the second to last block)
var secondToLastBlock = new byte[engine.BlockSizeBytes];
var secondToLastBlockStartIndex = (numberOfBlocks - 2) * engine.BlockSizeBytes;
Array.Copy(originalPayloadPaddedToBlockSize, secondToLastBlockStartIndex, secondToLastBlock, 0, engine.BlockSizeBytes);
var decryptedSecondToLastBlockBuffer = new byte[engine.BlockSizeBytes];
engine.ProcessSingleBlock(secondToLastBlock, decryptedSecondToLastBlockBuffer, 0);
var decryptedBlock = new BitString(decryptedSecondToLastBlockBuffer);
// Pad the payload to the nearest multiple of the block size using the last B−M bits of block cipher decryption of the second-to-last ciphertext block.
var amountToPad = (engine.BlockSizeBits - payload.BitLength % engine.BlockSizeBits);
if (amountToPad > 0)
{
payload = payload.ConcatenateBits(BitString.Substring(decryptedBlock, 0, amountToPad));
}
var payloadBytes = payload.ToBytes();
TransformText(payloadBytes, engine, numberOfBlocks, originalPayloadBitLength);
payload = new BitString(payloadBytes);
return(payload.ToBytes());
}
return(payload.ToBytes());
}
private void Encrypt(IModeBlockCipherParameters param, int numberOfBlocks, byte[] outBuffer)
{
var iv = param.Iv.GetDeepCopy().ToBytes();
// Pad the last partial plaintext block with 0 until it reaches the block size.
var paddedPayload = BitString.PadToModulus(param.Payload, _engine.BlockSizeBits).ToBytes();
// Encrypt the whole padded plaintext using the standard CBC mode.
// For each block
for (int i = 0; i < numberOfBlocks; i++)
{
// XOR IV onto current block payload
for (int j = 0; j < _engine.BlockSizeBytes; j++)
{
paddedPayload[i * _engine.BlockSizeBytes + j] ^= iv[j];
}
_engine.ProcessSingleBlock(paddedPayload, outBuffer, i);
// Update Iv with current block's outBuffer values
Array.Copy(outBuffer, i * _engine.BlockSizeBytes, iv, 0, _engine.BlockSizeBytes);
}
// Update the Param.Iv for the next call
for (int i = 0; i < _engine.BlockSizeBytes; i++)
{
param.Iv[i] = iv[i];
}
_ciphertextStealingTransform.TransformCiphertext(outBuffer, _engine, numberOfBlocks, param.Payload.BitLength);
}
public override SymmetricCounterResult ProcessPayload(IModeBlockCipherParameters param)
{
CheckPayloadRequirements(param.Payload);
var ivs = new List <BitString>();
var key = param.Key.ToBytes();
var actualBitsToProcess = param.Payload.BitLength;
param.Payload = BitString.PadToModulus(param.Payload, _engine.BlockSizeBits);
// CTR always utilizes engine in encrypt mode
var engineParam = new EngineInitParameters(BlockCipherDirections.Encrypt, key, param.UseInverseCipherMode);
_engine.Init(engineParam);
var numberOfBlocks = GetNumberOfBlocks(param.Payload.BitLength);
var outBuffer = GetOutputBuffer(param.Payload.BitLength);
ProcessPayload(param, numberOfBlocks, outBuffer, ivs);
return(new SymmetricCounterResult(new BitString(outBuffer).GetMostSignificantBits(actualBitsToProcess), ivs));
}
public SymmetricCounterResult ExtractIvs(ICounterModeBlockCipherParameters parameters)
{
BitString plainText, cipherText;
if (parameters.Direction == BlockCipherDirections.Encrypt)
{
plainText = parameters.Payload;
cipherText = parameters.Result;
}
else
{
plainText = parameters.Result;
cipherText = parameters.Payload;
}
plainText = BitString.PadToModulus(plainText, _engine.BlockSizeBits);
cipherText = BitString.PadToModulus(cipherText, _engine.BlockSizeBits);
var numberOfBlocks = GetNumberOfBlocks(plainText.BitLength);
var ivs = new List <BitString>();
var engineParam = new EngineInitParameters(BlockCipherDirections.Decrypt, parameters.Key.ToBytes(), parameters.UseInverseCipherMode);
_engine.Init(engineParam);
for (var i = 0; i < numberOfBlocks; i++)
{
var blockPt = plainText.MSBSubstring(i * _engine.BlockSizeBits, _engine.BlockSizeBits);
var blockCt = cipherText.MSBSubstring(i * _engine.BlockSizeBits, _engine.BlockSizeBits);
var xor = BitString.XOR(blockPt, blockCt).ToBytes();
var outBuffer = GetOutputBuffer(blockPt.BitLength);
_engine.ProcessSingleBlock(xor, outBuffer, 0);
ivs.Add(new BitString(outBuffer));
}
return(new SymmetricCounterResult(parameters.Result, ivs));
}
