NTLM Hash function in c#

NTLM.cs

/*
source:
  https://www.codeproject.com/Articles/328761/NTLM-Hash-Generator
*/

public static string Ntlm(string key)
{
	const uint INIT_A = 0x67452301;
	const uint INIT_B = 0xefcdab89;
	const uint INIT_C = 0x98badcfe;
	const uint INIT_D = 0x10325476;

	const uint SQRT_2 = 0x5a827999;
	const uint SQRT_3 = 0x6ed9eba1;

	char[] itoa16 = new[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

	uint[] nt_buffer = new uint[16];
	uint[] output = new uint[4];
	char[] hex_format = new char[32];

	//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	// Prepare the string for hash calculation
	//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	int i = 0;
	int length = key.Length;
	//The length of key need to be <= 27
	for (; i < length / 2; i++)
	{
		nt_buffer[i] = (key[2 * i] | ((uint)key[2 * i + 1] << 16));
	}

	//padding
	if (length % 2 == 1)
	{
		nt_buffer[i] = (uint)key[length - 1] | 0x800000;
	}
	else
	{
		nt_buffer[i] = 0x80;
	}

	//put the length
	nt_buffer[14] = (uint)length << 4;

	//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	// NTLM hash calculation
	//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	uint a = INIT_A;
	uint b = INIT_B;
	uint c = INIT_C;
	uint d = INIT_D;

	/* Round 1 */
	a += (d ^ (b & (c ^ d))) + nt_buffer[0]; a = (a << 3) | (a >> 29);
	d += (c ^ (a & (b ^ c))) + nt_buffer[1]; d = (d << 7) | (d >> 25);
	c += (b ^ (d & (a ^ b))) + nt_buffer[2]; c = (c << 11) | (c >> 21);
	b += (a ^ (c & (d ^ a))) + nt_buffer[3]; b = (b << 19) | (b >> 13);

	a += (d ^ (b & (c ^ d))) + nt_buffer[4]; a = (a << 3) | (a >> 29);
	d += (c ^ (a & (b ^ c))) + nt_buffer[5]; d = (d << 7) | (d >> 25);
	c += (b ^ (d & (a ^ b))) + nt_buffer[6]; c = (c << 11) | (c >> 21);
	b += (a ^ (c & (d ^ a))) + nt_buffer[7]; b = (b << 19) | (b >> 13);

	a += (d ^ (b & (c ^ d))) + nt_buffer[8]; a = (a << 3) | (a >> 29);
	d += (c ^ (a & (b ^ c))) + nt_buffer[9]; d = (d << 7) | (d >> 25);
	c += (b ^ (d & (a ^ b))) + nt_buffer[10]; c = (c << 11) | (c >> 21);
	b += (a ^ (c & (d ^ a))) + nt_buffer[11]; b = (b << 19) | (b >> 13);

	a += (d ^ (b & (c ^ d))) + nt_buffer[12]; a = (a << 3) | (a >> 29);
	d += (c ^ (a & (b ^ c))) + nt_buffer[13]; d = (d << 7) | (d >> 25);
	c += (b ^ (d & (a ^ b))) + nt_buffer[14]; c = (c << 11) | (c >> 21);
	b += (a ^ (c & (d ^ a))) + nt_buffer[15]; b = (b << 19) | (b >> 13);

	/* Round 2 */
	a += ((b & (c | d)) | (c & d)) + nt_buffer[0] + SQRT_2; a = (a << 3) | (a >> 29);
	d += ((a & (b | c)) | (b & c)) + nt_buffer[4] + SQRT_2; d = (d << 5) | (d >> 27);
	c += ((d & (a | b)) | (a & b)) + nt_buffer[8] + SQRT_2; c = (c << 9) | (c >> 23);
	b += ((c & (d | a)) | (d & a)) + nt_buffer[12] + SQRT_2; b = (b << 13) | (b >> 19);

	a += ((b & (c | d)) | (c & d)) + nt_buffer[1] + SQRT_2; a = (a << 3) | (a >> 29);
	d += ((a & (b | c)) | (b & c)) + nt_buffer[5] + SQRT_2; d = (d << 5) | (d >> 27);
	c += ((d & (a | b)) | (a & b)) + nt_buffer[9] + SQRT_2; c = (c << 9) | (c >> 23);
	b += ((c & (d | a)) | (d & a)) + nt_buffer[13] + SQRT_2; b = (b << 13) | (b >> 19);

	a += ((b & (c | d)) | (c & d)) + nt_buffer[2] + SQRT_2; a = (a << 3) | (a >> 29);
	d += ((a & (b | c)) | (b & c)) + nt_buffer[6] + SQRT_2; d = (d << 5) | (d >> 27);
	c += ((d & (a | b)) | (a & b)) + nt_buffer[10] + SQRT_2; c = (c << 9) | (c >> 23);
	b += ((c & (d | a)) | (d & a)) + nt_buffer[14] + SQRT_2; b = (b << 13) | (b >> 19);

	a += ((b & (c | d)) | (c & d)) + nt_buffer[3] + SQRT_2; a = (a << 3) | (a >> 29);
	d += ((a & (b | c)) | (b & c)) + nt_buffer[7] + SQRT_2; d = (d << 5) | (d >> 27);
	c += ((d & (a | b)) | (a & b)) + nt_buffer[11] + SQRT_2; c = (c << 9) | (c >> 23);
	b += ((c & (d | a)) | (d & a)) + nt_buffer[15] + SQRT_2; b = (b << 13) | (b >> 19);

	/* Round 3 */
	a += (d ^ c ^ b) + nt_buffer[0] + SQRT_3; a = (a << 3) | (a >> 29);
	d += (c ^ b ^ a) + nt_buffer[8] + SQRT_3; d = (d << 9) | (d >> 23);
	c += (b ^ a ^ d) + nt_buffer[4] + SQRT_3; c = (c << 11) | (c >> 21);
	b += (a ^ d ^ c) + nt_buffer[12] + SQRT_3; b = (b << 15) | (b >> 17);

	a += (d ^ c ^ b) + nt_buffer[2] + SQRT_3; a = (a << 3) | (a >> 29);
	d += (c ^ b ^ a) + nt_buffer[10] + SQRT_3; d = (d << 9) | (d >> 23);
	c += (b ^ a ^ d) + nt_buffer[6] + SQRT_3; c = (c << 11) | (c >> 21);
	b += (a ^ d ^ c) + nt_buffer[14] + SQRT_3; b = (b << 15) | (b >> 17);

	a += (d ^ c ^ b) + nt_buffer[1] + SQRT_3; a = (a << 3) | (a >> 29);
	d += (c ^ b ^ a) + nt_buffer[9] + SQRT_3; d = (d << 9) | (d >> 23);
	c += (b ^ a ^ d) + nt_buffer[5] + SQRT_3; c = (c << 11) | (c >> 21);
	b += (a ^ d ^ c) + nt_buffer[13] + SQRT_3; b = (b << 15) | (b >> 17);

	a += (d ^ c ^ b) + nt_buffer[3] + SQRT_3; a = (a << 3) | (a >> 29);
	d += (c ^ b ^ a) + nt_buffer[11] + SQRT_3; d = (d << 9) | (d >> 23);
	c += (b ^ a ^ d) + nt_buffer[7] + SQRT_3; c = (c << 11) | (c >> 21);
	b += (a ^ d ^ c) + nt_buffer[15] + SQRT_3; b = (b << 15) | (b >> 17);

	output[0] = a + INIT_A;
	output[1] = b + INIT_B;
	output[2] = c + INIT_C;
	output[3] = d + INIT_D;

	//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	// Convert the hash to hex (for being readable)
	//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	for (i = 0; i < 4; i++)
	{
		int j = 0;
		uint n = output[i];
		//iterate the bytes of the integer
		for (; j < 4; j++)
		{
			uint convert = n % 256;
			hex_format[i * 8 + j * 2 + 1] = itoa16[convert % 16];
			convert = convert / 16;
			hex_format[i * 8 + j * 2 + 0] = itoa16[convert % 16];
			n = n / 256;
		}
	}

	return string.Join(string.Empty, hex_format);
}