sha256.cpp

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#include "sha256.hpp"

using namespace cryptoTools;


// =========================== Standard functions of the specification

// Macros are used instead of functions for better performances

#define ROTR(n,x) ( ((x)>>(n)) | ((x)<<(32-(n))) )
#define SHR(n,x)  ((x)>>(n))
#define CH(x,y,z)   ( ((x)&(y)) ^ ((~x)&(z)) )
#define MAJ(x,y,z) ( ((x)&(y)) ^ ((x)&(z)) ^ ((y)&(z)) )
#define BIGSIGMA0(x) ( ROTR(2,(x)) ^ ROTR(13,(x)) ^ ROTR(22,(x)) )
#define BIGSIGMA1(x) ( ROTR(6,(x)) ^ ROTR(11,(x)) ^ ROTR(25,(x)) )
#define SMALLSIGMA0(x) ( ROTR(7,(x)) ^ ROTR(18,(x)) ^ SHR(3,(x)) )
#define SMALLSIGMA1(x) ( ROTR(17,(x)) ^ ROTR(19,(x)) ^ SHR(10,(x)) )


// ================================================= Constants

// The constants to which the internal state must be initialised.
uint32_t init256[8] =
{
        0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
        0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
};


// The constants to use in each step of the main loop of a round.
uint32_t K256[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
};
                                                                           


// ================================================== public functions


void SHA256::preprocess(std::vector<unsigned char> initialMessage)
{
        // padding the initial message by...
        l = initialMessage.size()*8;
        // ... adding 10000000
        initialMessage.push_back(0x80);
        // ... adding the correct amount of zeroes
        unsigned int k = ( (448-(l+8))%512 >= 0) ?  (448-(l+8))%512 :  512+(448-(l+8))%512;
        for (unsigned int i=0; i<k; i+=8)
                initialMessage.push_back(0x00);
        // ... and appending the length of the input.
        initialMessage.push_back((l>>56)%0x100);
        initialMessage.push_back((l>>48)%0x100);
        initialMessage.push_back((l>>40)%0x100);
        initialMessage.push_back((l>>32)%0x100);
        initialMessage.push_back((l>>24)%0x100);
        initialMessage.push_back((l>>16)%0x100);
        initialMessage.push_back((l>>8 )%0x100);
        initialMessage.push_back(l%0x100);
        // Turning the initial byte message into a 32words one
        M.clear();
        for (unsigned int i=0; i<initialMessage.size() ; i+=4)
                M.push_back(  (initialMessage[i]   << 24)
                            | (initialMessage[i+1] << 16)
                            | (initialMessage[i+2] << 8)
                            |  initialMessage[i+3] );
        // initialising the hash values H_i
        for (unsigned int i=0; i<8; i++)
                H[i] = init256[i];
}



void SHA256::round(unsigned int counter)
{
        uint32_t W[64], T1, T2;
        // initializing the working variables
        a = H[0]; b = H[1];
        c = H[2]; d = H[3];
        e = H[4]; f = H[5];
        g = H[6]; h = H[7];
        // loop over the currently processed hash
        for (unsigned int t=0; t<64; t++)
        {
                // preparing the message schedule
                W[t] = (t<=15) ?  M[counter+t] : SMALLSIGMA1(W[t-2]) + W[t-7] + SMALLSIGMA0(W[t-15]) + W[t-16];
                // Re-assigning the temporary variables
                T1 = h + BIGSIGMA1(e) + CH(e,f,g) + K256[t] + W[t];
                T2 = BIGSIGMA0(a) + MAJ(a,b,c) ;
                h = g; g = f; f = e;
                e = d + T1;
                d = c; c = b; b = a;
                a = T1 + T2;
        }
        // computing the ith hash value H[8]
        H[0] += a; H[1] += b;
        H[2] += c; H[3] += d;
        H[4] += e; H[5] += f;
        H[6] += g; H[7] += h;
}


void SHA256::hash(std::vector<unsigned char> initialMessage)
{
        preprocess(initialMessage);
        for (unsigned int counter=0; counter<M.size(); counter+=16)
                round(counter);
}


std::vector<uint8_t> SHA256::getHash()
{
        std::vector<uint8_t> digest;
        for (unsigned int i=0; i<8; i++)
        {
                digest.push_back( (H[i]>>24) % 0x100);
                digest.push_back( (H[i]>>16) % 0x100);
                digest.push_back( (H[i]>>8)  % 0x100);
                digest.push_back(  H[i]      % 0x100);
        }
        return digest;
}


std::string SHA256::getType()
{
        return "SHA-256";
}


uint32_t SHA256::getHashLength()
{
        return 256;
}

#undef ROTR
#undef SHR
#undef CH
#undef MAJ
#undef BIGSIGMA0
#undef BIGSIGMA1
#undef SMALLSIGMA0
#undef SMALLSIGMA1