/// <summary>
/// Call this method to format correctly for ParallelHash
/// </summary>
/// <param name="message">BitString representation of message</param>
/// <param name="cSHAKE">A cSHAKE module</param>
/// <param name="capacity">Capacity</param>
/// <param name="blockSize">The desired block size in bytes</param>
/// <param name="xof">Is it xof mode?</param>
/// <returns>Formatted message before calling Keccak</returns>
public static BitString FormatMessage(BitString message, CSHAKE.CSHAKE cSHAKE, int digestLength, int capacity, int blockSize, bool xof)
{
// 1. n = ⌈ (len(X)/8) / B ⌉.
var numberOfBlocks = ((message.BitLength / 8) + blockSize - 1) / blockSize;
// 2. z = left_encode(B).
var newMessage = Sha3DerivedHelpers.LeftEncode(Sha3DerivedHelpers.IntToBitString(blockSize));
// 3. for i = 0 to n−1:
// z = z || cSHAKE128(substring(X, i*B*8, (i+1)*B*8), 256, "", "").
var strings = new List <BitString>();
var hashFunction = new HashFunction {
DigestLength = capacity, Capacity = capacity
};
for (var i = 0; i < numberOfBlocks; i++)
{
var substring = Sha3DerivedHelpers.SubString(message, i * blockSize * 8, (i + 1) * blockSize * 8);
strings.Add(cSHAKE.HashMessage(hashFunction, substring, "").Digest);
}
for (int i = 0; i < numberOfBlocks; i++)
{
newMessage = BitString.ConcatenateBits(newMessage, strings[i]);
}
// 4. z = z || right_encode(n) || right_encode(L).
newMessage = BitString.ConcatenateBits(newMessage, Sha3DerivedHelpers.RightEncode(Sha3DerivedHelpers.IntToBitString(numberOfBlocks)));
if (xof)
{
newMessage = BitString.ConcatenateBits(newMessage, Sha3DerivedHelpers.RightEncode(BitString.Zeroes(8)));
}
else
{
newMessage = BitString.ConcatenateBits(newMessage, Sha3DerivedHelpers.RightEncode(Sha3DerivedHelpers.IntToBitString(digestLength)));
}
return(newMessage);
}
// These functions are for portability
private void Init()
{
_message = new BitString(0);
_cSHAKE = new CSHAKE.CSHAKE();
}
