public static byte[] GetHash(byte[] input)
{
if (null == input)
throw new System.ArgumentNullException("input", "Unable to calculate hash over null input data");
//Intitial values defined in RFC 1321
ABCDStruct abcd = new ABCDStruct();
abcd.A = 0x67452301;
abcd.B = 0xefcdab89;
abcd.C = 0x98badcfe;
abcd.D = 0x10325476;
//We pass in the input array by block, the final block of data must be handled specialy for padding & length embeding
int startIndex = 0;
while (startIndex <= input.Length - 64)
{
MD5Core.GetHashBlock(input, ref abcd, startIndex);
startIndex += 64;
}
// The final data block.
return MD5Core.GetHashFinalBlock(input, startIndex, input.Length - startIndex, abcd, (Int64)input.Length * 8);
}
internal static byte[] GetHashFinalBlock(byte[] input, int ibStart, int cbSize, ABCDStruct ABCD, Int64 len)
{
byte[] working = new byte[64];
byte[] length = BitConverter.GetBytes(len);
//Padding is a single bit 1, followed by the number of 0s required to make size congruent to 448 modulo 512. Step 1 of RFC 1321
//The CLR ensures that our buffer is 0-assigned, we don't need to explicitly set it. This is why it ends up being quicker to just
//use a temporary array rather then doing in-place assignment (5% for small inputs)
Array.Copy(input, ibStart, working, 0, cbSize);
working[cbSize] = 0x80;
//We have enough room to store the length in this chunk
if (cbSize < 56)
{
Array.Copy(length, 0, working, 56, 8);
GetHashBlock(working, ref ABCD, 0);
}
else //We need an aditional chunk to store the length
{
GetHashBlock(working, ref ABCD, 0);
//Create an entirely new chunk due to the 0-assigned trick mentioned above, to avoid an extra function call clearing the array
working = new byte[64];
Array.Copy(length, 0, working, 56, 8);
GetHashBlock(working, ref ABCD, 0);
}
byte[] output = new byte[16];
Array.Copy(BitConverter.GetBytes(ABCD.A), 0, output, 0, 4);
Array.Copy(BitConverter.GetBytes(ABCD.B), 0, output, 4, 4);
Array.Copy(BitConverter.GetBytes(ABCD.C), 0, output, 8, 4);
Array.Copy(BitConverter.GetBytes(ABCD.D), 0, output, 12, 4);
return output;
}
// Performs a single block transform of MD5 for a given set of ABCD inputs
/* If implementing your own hashing framework, be sure to set the initial ABCD correctly according to RFC 1321:
// A = 0x67452301;
// B = 0xefcdab89;
// C = 0x98badcfe;
// D = 0x10325476;
*/
internal static void GetHashBlock(byte[] input, ref ABCDStruct ABCDValue, int ibStart)
{
uint[] temp = Converter(input, ibStart);
uint a = ABCDValue.A;
uint b = ABCDValue.B;
uint c = ABCDValue.C;
uint d = ABCDValue.D;
a = r1(a, b, c, d, temp[0], 7, 0xd76aa478);
d = r1(d, a, b, c, temp[1], 12, 0xe8c7b756);
c = r1(c, d, a, b, temp[2], 17, 0x242070db);
b = r1(b, c, d, a, temp[3], 22, 0xc1bdceee);
a = r1(a, b, c, d, temp[4], 7, 0xf57c0faf);
d = r1(d, a, b, c, temp[5], 12, 0x4787c62a);
c = r1(c, d, a, b, temp[6], 17, 0xa8304613);
b = r1(b, c, d, a, temp[7], 22, 0xfd469501);
a = r1(a, b, c, d, temp[8], 7, 0x698098d8);
d = r1(d, a, b, c, temp[9], 12, 0x8b44f7af);
c = r1(c, d, a, b, temp[10], 17, 0xffff5bb1);
b = r1(b, c, d, a, temp[11], 22, 0x895cd7be);
a = r1(a, b, c, d, temp[12], 7, 0x6b901122);
d = r1(d, a, b, c, temp[13], 12, 0xfd987193);
c = r1(c, d, a, b, temp[14], 17, 0xa679438e);
b = r1(b, c, d, a, temp[15], 22, 0x49b40821);
a = r2(a, b, c, d, temp[1], 5, 0xf61e2562);
d = r2(d, a, b, c, temp[6], 9, 0xc040b340);
c = r2(c, d, a, b, temp[11], 14, 0x265e5a51);
b = r2(b, c, d, a, temp[0], 20, 0xe9b6c7aa);
a = r2(a, b, c, d, temp[5], 5, 0xd62f105d);
d = r2(d, a, b, c, temp[10], 9, 0x02441453);
c = r2(c, d, a, b, temp[15], 14, 0xd8a1e681);
b = r2(b, c, d, a, temp[4], 20, 0xe7d3fbc8);
a = r2(a, b, c, d, temp[9], 5, 0x21e1cde6);
d = r2(d, a, b, c, temp[14], 9, 0xc33707d6);
c = r2(c, d, a, b, temp[3], 14, 0xf4d50d87);
b = r2(b, c, d, a, temp[8], 20, 0x455a14ed);
a = r2(a, b, c, d, temp[13], 5, 0xa9e3e905);
d = r2(d, a, b, c, temp[2], 9, 0xfcefa3f8);
c = r2(c, d, a, b, temp[7], 14, 0x676f02d9);
b = r2(b, c, d, a, temp[12], 20, 0x8d2a4c8a);
a = r3(a, b, c, d, temp[5], 4, 0xfffa3942);
d = r3(d, a, b, c, temp[8], 11, 0x8771f681);
c = r3(c, d, a, b, temp[11], 16, 0x6d9d6122);
b = r3(b, c, d, a, temp[14], 23, 0xfde5380c);
a = r3(a, b, c, d, temp[1], 4, 0xa4beea44);
d = r3(d, a, b, c, temp[4], 11, 0x4bdecfa9);
c = r3(c, d, a, b, temp[7], 16, 0xf6bb4b60);
b = r3(b, c, d, a, temp[10], 23, 0xbebfbc70);
a = r3(a, b, c, d, temp[13], 4, 0x289b7ec6);
d = r3(d, a, b, c, temp[0], 11, 0xeaa127fa);
c = r3(c, d, a, b, temp[3], 16, 0xd4ef3085);
b = r3(b, c, d, a, temp[6], 23, 0x04881d05);
a = r3(a, b, c, d, temp[9], 4, 0xd9d4d039);
d = r3(d, a, b, c, temp[12], 11, 0xe6db99e5);
c = r3(c, d, a, b, temp[15], 16, 0x1fa27cf8);
b = r3(b, c, d, a, temp[2], 23, 0xc4ac5665);
a = r4(a, b, c, d, temp[0], 6, 0xf4292244);
d = r4(d, a, b, c, temp[7], 10, 0x432aff97);
c = r4(c, d, a, b, temp[14], 15, 0xab9423a7);
b = r4(b, c, d, a, temp[5], 21, 0xfc93a039);
a = r4(a, b, c, d, temp[12], 6, 0x655b59c3);
d = r4(d, a, b, c, temp[3], 10, 0x8f0ccc92);
c = r4(c, d, a, b, temp[10], 15, 0xffeff47d);
b = r4(b, c, d, a, temp[1], 21, 0x85845dd1);
a = r4(a, b, c, d, temp[8], 6, 0x6fa87e4f);
d = r4(d, a, b, c, temp[15], 10, 0xfe2ce6e0);
c = r4(c, d, a, b, temp[6], 15, 0xa3014314);
b = r4(b, c, d, a, temp[13], 21, 0x4e0811a1);
a = r4(a, b, c, d, temp[4], 6, 0xf7537e82);
d = r4(d, a, b, c, temp[11], 10, 0xbd3af235);
c = r4(c, d, a, b, temp[2], 15, 0x2ad7d2bb);
b = r4(b, c, d, a, temp[9], 21, 0xeb86d391);
ABCDValue.A = unchecked(a + ABCDValue.A);
ABCDValue.B = unchecked(b + ABCDValue.B);
ABCDValue.C = unchecked(c + ABCDValue.C);
ABCDValue.D = unchecked(d + ABCDValue.D);
return;
}