@nullius, I wonder if you would provide your opinion on the following simple algo I devised to determine Nfactor (
https://github.com/floodyberry/scrypt-jane) based on previous block hash.
I understand that:
1) This should probably look back to a further level of confirmed block.
2) A vanityaddress could be used to "game the system" by generating a specific char for last position along with the required PoW, though this would require an extra bit of work over non-bad actors.
Apart from that, I would expect a 25% chance overall for each of the 4 options.
unsigned char CBlockHeader::GetNfactor() const
{
std::string spb = hashPrevBlock.ToString();
std::string lasthashchar = spb.substr(block_length,1);
unsigned char Nfactor = 20;
if((spb == "0000000000000000000000000000000000000000000000000000000000000000")){
Nfactor = 4;} // Genesis, all chains.
else if((lasthashchar == "0") || (lasthashchar == "1") || (lasthashchar == "2") || (lasthashchar == "3")){
Nfactor = 18;}
else if((lasthashchar == "4") || (lasthashchar == "5") || (lasthashchar == "6") || (lasthashchar == "7")){
Nfactor = 19;}
else if((lasthashchar == "8") || (lasthashchar == "9") || (lasthashchar == "a") || (lasthashchar == "b")){
Nfactor = 20;}
else if((lasthashchar == "c") || (lasthashchar == "d") || (lasthashchar == "e") || (lasthashchar == "f")){
Nfactor = 21;}
return Nfactor;
}