System.Security.Cryptography.RijndaelTransform.RijndaelTransform C# (CSharp) Method

		public RijndaelTransform (Rijndael algo, bool encryption, byte[] key, byte[] iv) : base (algo, encryption, iv)
		{
			if (key == null)
				throw new CryptographicException ("key is null");
			if ((iv != null) && (iv.Length != (algo.BlockSize >> 3))) {
				string msg = Locale.GetText ("IV length is invalid ({0} bytes), it should be {1} bytes long.",
					iv.Length, (algo.BlockSize >> 3));
				throw new CryptographicException (msg);
			}

			int keySize = key.Length;
			if (keySize != 16 && keySize != 24 && keySize != 32) {
				string msg = Locale.GetText ("Key is too small ({0} bytes), it should be {1}, {2} or {3} bytes long.",
					keySize, 16, 24, 32);
				throw new CryptographicException (msg);
			}
			keySize <<= 3; // bytes -> bits
			int blockSize = algo.BlockSize;

			this.Nb = (blockSize >> 5); // div 32
			this.Nk = (keySize >> 5); // div 32
	
			if (Nb == 8 || Nk == 8) {
				Nr = 14;
			} else if (Nb == 6 || Nk == 6) {
				Nr = 12;
			} else {
				Nr = 10;
			}
	
			// Setup Expanded Key
			int exKeySize = Nb * (Nr+1);
			UInt32[] exKey = new UInt32[exKeySize];
			int pos = 0;
			for (int i=0; i < Nk; i++) {
				UInt32 value = ((UInt32)key [pos++] << 24);
				value |= ((UInt32)key[pos++] << 16);
				value |= ((UInt32)key[pos++] << 8);
				value |= ((UInt32)key[pos++]);
				exKey [i] = value;
			}
	
			for (int i = Nk; i < exKeySize; i++) {
				UInt32 temp = exKey [i-1];
				if (i % Nk == 0) {
					UInt32 rot = (UInt32) ((temp << 8) | ((temp >> 24) & 0xff));
					temp = SubByte (rot) ^ Rcon [i / Nk];
				} else if (Nk > 6 && (i % Nk) == 4) {
					temp = SubByte (temp);
				}
				exKey [i] = exKey [i-Nk] ^ temp;
			}

			if (!encryption && (algo.Mode == CipherMode.ECB || algo.Mode == CipherMode.CBC)) {
				for (int i = 0, k = exKeySize - Nb; i < k; i += Nb, k -= Nb) {
					for (int j = 0; j < Nb; j ++) {
						uint temp = exKey[i + j];
						exKey[i + j] = exKey[k + j];
						exKey[k + j] = temp;
					}
				}

				for (int i = Nb; i < exKey.Length - Nb; i ++) {
					exKey[i] =
						iT0[SBox[(exKey[i] >> 24)]] ^
						iT1[SBox[(byte)(exKey[i] >> 16)]] ^
						iT2[SBox[(byte)(exKey[i] >> 8)]] ^
						iT3[SBox[(byte)exKey[i]]];
				}
			}
			expandedKey = exKey;
		}