/// <summary>
/// Creates a new managed transform instance, reading necessary
/// setting values from the provided <see cref="ISymmetricAlgorithm" />
/// instance.
/// </summary>
/// <param name="algorithm">
/// A <see cref="ISymmetricAlgorithm" /> instance from which to take
/// setting values.
/// </param>
/// <param name="rgbIv">
/// The initialization vector to use.
/// </param>
/// <param name="transformDirection">
/// The direction of the transform (encryption or decryption).
/// </param>
/// <param name="endianness">
/// The endianness convention for the algorithm.
/// </param>
protected ManagedTransformBase(ISymmetricAlgorithm algorithm, byte[] rgbIv, TransformDirection transformDirection, Endianness endianness)
{
Endianness = endianness;
_bytesToWords = endianness == Endianness.Little
? (BytesToWords)Utils.BytesToWordsLittleEndian
: Utils.BytesToWordsBigEndian;
_writeWordsIntoBytes = endianness == Endianness.Little
? (WriteWordsIntoBytes)Utils.WriteWordsIntoBytesLittleEndian
: Utils.WriteWordsIntoBytesBigEndian;
PaddingMode = algorithm.Padding;
BlockSizeBytes = algorithm.BlockSize >> 3;
Mode = algorithm.ExtendedMode;
NonceCombinationMode = algorithm.NonceCombinationMode;
_registerShiftSize = algorithm.RegisterShiftSize;
_feedbackValue = new byte[BlockSizeBytes];
_iv = new byte[BlockSizeBytes];
if (rgbIv != null)
{
rgbIv.CopyTo(_feedbackValue, 0);
rgbIv.CopyTo(_iv, 0);
if (Mode == ExtendedCipherMode.CTR)
{
switch (NonceCombinationMode)
{
case NonceCombinationMode.Concatenate:
_counterSize = BlockSizeBytes - rgbIv.Length;
_counter = new byte[_counterSize];
break;
case NonceCombinationMode.Xor:
_counterSize = BlockSizeBytes;
_counter = new byte[_counterSize];
break;
case NonceCombinationMode.Add:
_counterSize = BlockSizeBytes;
_counter = (byte[])_feedbackValue.Clone();
break;
}
_initial = true;
}
}
_transformDirection = transformDirection;
}