/// <summary>
/// Gets the hash block.
/// </summary>
/// <remarks>
/// Performs a single block transform of MD5 for a given set of ABCD inputs
/// <para />
/// 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;
/// </remarks>
/// <param name="input">The input.</param>
/// <param name="abcdValue">The abcd value.</param>
/// <param name="ibStart">The attribute start.</param>
internal static void GetHashBlock(byte[] input, ref ABCDStruct abcdValue, int ibStart)
{
var temp = Converter(input, ibStart);
var a = abcdValue.A;
var b = abcdValue.B;
var c = abcdValue.C;
var 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);
}
internal static byte[] GetHashFinalBlock(byte[] input, int ibStart, int cbSize, ABCDStruct abcd, Int64 len)
{
var working = new byte[64];
var 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 additional 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);
}
var 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);
}