do you need to independently create a genesis block for a new altcoin?

Question

So if one was to try to create an altcoin that was a fork of the bitcoin code would he/she have to create a genesis block independently first?

static CBlock CreateGenesisBlock(uint32_t nTime, uint32_t nNonce, uint32_t nBits, int32_t nVersion, const CAmount& genesisReward)
{
    const char* pszTimestamp = "anything you want";
    const CScript genesisOutputScript = CScript() << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f") << OP_CHECKSIG;
    return CreateGenesisBlock(pszTimestamp, genesisOutputScript, nTime, nNonce, nBits, nVersion, genesisReward);
}

Is changing the variable for pszTimestamp in the above function from chainparams.cpp sufficient?

If that's all that's necessary, then what is the purpose of this "gensis block generation script"*?

*From this question.

Answer 1

In old versions of the Bitcoin Core codebase, the genesis block was verified as a normal block. All normal rules had to apply to it, including proof of work and difficulty. This meant that if you would modify the contents of the genesis block arbitrarily, it almost certainly would not validate anymore.

Since the genesis block is actually part of the definition of the chain, there is no real need to verify it. In more recent versions, the genesis block is just valid by fiat. This means that when using such a codebase, no complicated script that "mines" the genesis block is needed anymore to define a new chain.

Answer 2

did u managed to start a new chain? I also try the same but i modiefied a lot iin chainparams.cpp already without success and i also created genesis block extern with a python script but the main code doesnt accept it (assertion failed) so looks like i m missing something hidden in the code ;) set checkpoints to o uint256= "0x" is right no? cheers

Answer 3

i've start to do the same. I think have resolve the problem of the 2 assert in chainparams.cpp (no more error on running myaltcoind file) with this script ( Altcoin Genesis block fails after changing block reward) that hash genesis:

assert(consensus.hashGenesisBlock == uint256S("0x12a765e3...."));
assert(genesis.hashMerkleRoot == uint256S("0x97ded9....."));

BUT i sill have an error when launching myaltcoind file:
ERROR : error : A fatal internal error occured, see debog.log for details Segmentation fault (core dumped)

And the debug.log file don't give a useful problem. here's :

2018-02-26 17:37:41 Coin4coin version v0.15.1.0-unk
2018-02-26 17:37:41 InitParameterInteraction: parameter interaction: -whitelistforcerelay=1 -> setting -whitelistrelay=1
2018-02-26 17:37:41 Assuming ancestors of block 59c9b9d3fec105bdc716d84caa7579503d5b05b73618d0bf2d5fa639f780a011 have valid signatures.
2018-02-26 17:37:41 Setting nMinimumChainWork=00000000000000000000000000000000000000000000002ebcfe2dd9eff82666
2018-02-26 17:37:41 Using the 'standard' SHA256 implementation
2018-02-26 17:37:41 Default data directory /home/prof/.coin4coin
2018-02-26 17:37:41 Using data directory /home/prof/.coin4coin
2018-02-26 17:37:41 Using config file /home/prof/.coin4coin/coin4coin.conf
2018-02-26 17:37:41 Using at most 125 automatic connections (1024 file descriptors available)
2018-02-26 17:37:41 Using 16 MiB out of 32/2 requested for signature cache, able to store 524288 elements
2018-02-26 17:37:41 Using 16 MiB out of 32/2 requested for script execution cache, able to store 524288 elements
2018-02-26 17:37:41 Using 0 threads for script verification
2018-02-26 17:37:41 scheduler thread start
2018-02-26 17:37:41 HTTP: creating work queue of depth 16
2018-02-26 17:37:41 No rpcpassword set - using random cookie authentication
2018-02-26 17:37:41 Generated RPC authentication cookie /home/prof/.coin4coin/.cookie
2018-02-26 17:37:41 HTTP: starting 4 worker threads
2018-02-26 17:37:41 init message: Verifying wallet(s)...
2018-02-26 17:37:41 Using BerkeleyDB version Berkeley DB 4.8.30: (April  9, 2010)
2018-02-26 17:37:41 Using wallet wallet.dat
2018-02-26 17:37:41 CDBEnv::Open: LogDir=/home/prof/.coin4coin/database ErrorFile=/home/prof/.coin4coin/db.log
2018-02-26 17:37:41 Cache configuration:
2018-02-26 17:37:41 * Using 2.0MiB for block index database
2018-02-26 17:37:41 * Using 8.0MiB for chain state database
2018-02-26 17:37:41 * Using 440.0MiB for in-memory UTXO set (plus up to 286.1MiB of unused mempool space)
2018-02-26 17:37:41 init message: Loading block index...
2018-02-26 17:37:41 Opening LevelDB in /home/prof/.coin4coin/blocks/index
2018-02-26 17:37:41 Opened LevelDB successfully
2018-02-26 17:37:41 Using obfuscation key for /home/prof/.coin4coin/blocks/index: 0000000000000000
2018-02-26 17:37:41 LoadBlockIndexDB: last block file = 0
2018-02-26 17:37:41 LoadBlockIndexDB: last block file info: CBlockFileInfo(blocks=0, size=0, heights=0...0, time=1970-01-01...1970-01-01)
2018-02-26 17:37:41 Checking all blk files are present...
2018-02-26 17:37:41 LoadBlockIndexDB: transaction index disabled
2018-02-26 17:37:41 Initializing databases...
2018-02-26 17:37:41 Pre-allocating up to position 0x1000000 in blk00000.dat
2018-02-26 17:37:41 Opening LevelDB in /home/prof/.coin4coin/chainstate
2018-02-26 17:37:41 Opened LevelDB successfully
2018-02-26 17:37:41 Using obfuscation key for /home/prof/.coin4coin/chainstate: 5ede9e4227910002
2018-02-26 17:37:41 init message: Rewinding blocks...
2018-02-26 17:37:41  block index              92ms
2018-02-26 17:37:41 init message: Loading wallet...
2018-02-26 17:37:41 nFileVersion = 150100
2018-02-26 17:37:41 Keys: 2002 plaintext, 0 encrypted, 2002 w/ metadata, 2002 total
2018-02-26 17:37:42  wallet                   55ms
2018-02-26 17:37:42 setKeyPool.size() = 2000
2018-02-26 17:37:42 mapWallet.size() = 0
2018-02-26 17:37:42 mapAddressBook.size() = 1
2018-02-26 17:37:42 ERROR: ReadBlockFromDisk: Errors in block header at CBlockDiskPos(nFile=0, nPos=8)
2018-02-26 17:37:42 *** Failed to read block
2018-02-26 17:37:42 Error: Error: A fatal internal error occurred, see debug.log for details 

Can i have some help please ?