After inspecting bitcoin's hashing section, I discovered this in hash.cpp
unsigned int MurmurHash3(unsigned int nHashSeed, const std::vector<unsigned char>& vDataToHash)
{
// The following is MurmurHash3 (x86_32), see http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
uint32_t h1 = nHashSeed;
const uint32_t c1 = 0xcc9e2d51;
const uint32_t c2 = 0x1b873593;
const int nblocks = vDataToHash.size() / 4;
//----------
// body
const uint32_t * blocks = (const uint32_t *)(&vDataToHash[0] + nblocks*4);
for(int i = -nblocks; i; i++)
{
uint32_t k1 = blocks[i];
k1 *= c1;
k1 = ROTL32(k1,15);
k1 *= c2;
h1 ^= k1;
h1 = ROTL32(h1,13);
h1 = h1*5+0xe6546b64;
}
//----------
// tail
const uint8_t * tail = (const uint8_t*)(&vDataToHash[0] + nblocks*4);
uint32_t k1 = 0;
switch(vDataToHash.size() & 3)
{
case 3: k1 ^= tail[2] << 16;
case 2: k1 ^= tail[1] << 8;
case 1: k1 ^= tail[0];
k1 *= c1; k1 = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
};
//----------
// finalization
h1 ^= vDataToHash.size();
h1 ^= h1 >> 16;
h1 *= 0x85ebca6b;
h1 ^= h1 >> 13;
h1 *= 0xc2b2ae35;
h1 ^= h1 >> 16;
return h1;
}
What/why is there murmurhash in the middle of bitcoin?
What does it do, excatly, and why have I never heard of this anywhere? I'm not very proficient with cryptography, so a detailed explanation would be great
Thanks,
