sha256.cpp

#include <iostream>

uint32_t rotateInt(uint32_t inputWord, int numberOfBitsToRotate) 
{
    int bitWidth = sizeof(inputWord) * 8;
    // Rotating 32 bits on a 32-bit integer is the same as rotating 0 bits;
    //   33 bits -> 1 bit; etc.
    numberOfBitsToRotate = numberOfBitsToRotate % bitWidth;

    uint32_t tempWord = inputWord;

    // Rotate input to the right
    inputWord = inputWord >> numberOfBitsToRotate;

    // Build mask for carried over bits
    tempWord = tempWord << (bitWidth - numberOfBitsToRotate);

    return inputWord | tempWord;
}

int Ch(int x, int y, int z)
{
    return ((x & y) ^ (~x & z));
}

int Maj(int x, int y, int z)
{
    return ((x & y) ^ (x & z) ^ (y & z));
}

int Sig0f(int x)
{
    return(rotateInt(x, 2) ^ rotateInt(x, 13) ^ rotateInt(x, 22));
}

int Sig1f(int x)
{
    return(rotateInt(x, 6) ^ rotateInt(x, 11) ^ rotateInt(x,25));
}

uint32_t sig0(uint32_t x)
{
    return(rotateInt(x, 7) ^ rotateInt(x, 18) ^ (x >> 3));
}

uint32_t sig1(uint32_t x)
{
    return(rotateInt(x, 17) ^ rotateInt(x, 19) ^ (x >> 10));
}

void hash(uint32_t *input, int bitlength, uint32_t *outputlocation)
{
    uint32_t H_0[8] = { 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19 };

    uint32_t K[64] = {0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
    0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
    0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
    0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
    0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
    0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2};

    int wordlength = bitlength / 32 + 1;
    int k = (512 * 512 - bitlength - 1) % 512;
    uint32_t message[10000] = {};

    for(int i = 0; i < wordlength; i++)
        message[i] = input[i];

    if(bitlength % 32 != 0)
        message[bitlength / 32] = message[bitlength / 32] | (1 << (32 - 1 - bitlength % 32));
    else
        message[bitlength / 32] = 1 << 31;
    
    uint32_t rounds;

    // Assuming our data isn't bigger than 2^32 bits long... which it won't be for a block hash.
    if(wordlength % 16 == 0 || wordlength % 16 == 15)
    {
        message[wordlength + 15 + 16 - wordlength % 16] = bitlength;
        rounds = wordlength / 16 + 2;
    }
    else
    {
        message[wordlength + 15 - wordlength % 16] = bitlength;
        rounds = wordlength / 16 + 1;
    }
        
    uint32_t M[32][16];

    for(int i = 0; i < 16; i++)
        for(int j = 0; j <= rounds; j++)
            M[j][i] = message[i + j * 16];
    
    uint32_t H[32][8];

    for(int i = 0; i < 8; i++)
        H[0][i] = H_0[i];

    // Here our hash function rounds actually start.
    for(int i = 1; i <= rounds; i++)
    {
        uint32_t a = H[i-1][0];
        uint32_t b = H[i-1][1];
        uint32_t c = H[i-1][2];
        uint32_t d = H[i-1][3];
        uint32_t e = H[i-1][4];
        uint32_t f = H[i-1][5];
        uint32_t g = H[i-1][6];
        uint32_t h = H[i-1][7];

        uint32_t W[64];

        for(int j = 0; j < 64; j++)
        {
            uint32_t ch = Ch(e, f, g);
            uint32_t maj = Maj(a, b, c);
            uint32_t Sig0 = Sig0f(a);
            uint32_t Sig1 = Sig1f(e);

            if(j < 16)
                W[j] = M[i-1][j];
            else
                W[j] = sig1(W[j-2]) + W[j-7] + sig0(W[j-15]) + W[j-16];
            
            uint32_t T1 = h + Sig1 + ch + K[j] + W[j];
            uint32_t T2 = Sig0 + maj;
            h = g;
            g = f;
            f = e;
            e = d + T1;
            d = c;
            c = b;
            b = a;
            a = T1 + T2;
        }

        H[i][0] = a + H[i-1][0];
        H[i][1] = b + H[i-1][1];
        H[i][2] = c + H[i-1][2];
        H[i][3] = d + H[i-1][3];
        H[i][4] = e + H[i-1][4];
        H[i][5] = f + H[i-1][5];
        H[i][6] = g + H[i-1][6];
        H[i][7] = h + H[i-1][7];
    }

    for(int i = 0; i < 8; i++)
        outputlocation[i] = H[rounds][i];
}