Bitcoin Source Code (5): Changing the block validation rules

Changing the block validation rules in the Core Code of the Bitcoin source code is a significant undertaking that requires a deep understanding of the blockchain’s architecture and design principles. Additionally, any changes to the Core Code could potentially have far-reaching effects on the stability and security of the network. As such, it is essential to thoroughly test any modifications before deploying them in a production environment.

To change the block validation rules, you will need to modify the consensus code in the Core Code section of the Bitcoin source code. This code includes the consensus rules that determine how new blocks are validated and added to the blockchain.

Here is an example of how to change the block validation rules to require a higher difficulty for new blocks:

1. Modify the consensus code in the Core Code section of the Bitcoin source code. Specifically, you will need to modify the GetNextWorkRequired function in the consensus.cpp file. This function is responsible for calculating the difficulty target for new blocks based on the previous block’s difficulty target and the time it took to mine the previous block.

Here is the original code for the GetNextWorkRequired function:

uint32_t GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader* pblock, const Consensus::Params& consensusParams) {
    // Get the last block's difficulty target
    uint32_t nLastBits = pindexLast->nBits;
    
    // Calculate the time between the last block and the previous block
    int64_t nActualTimespan = pindexLast->GetBlockTime() - pindexLast->pprev->GetBlockTime();
    
    // Calculate the ideal timespan
    int64_t nTargetTimespan = consensusParams.nTargetSpacing * (pindexLast->nHeight + 1);
    
    // Adjust the difficulty target based on the actual timespan and the ideal timespan
    int64_t nNewBits = nLastBits;
    nNewBits *= nActualTimespan;
    nNewBits /= nTargetTimespan;
    
    // Limit the difficulty adjustment to a factor of 4x or 0.25x
    if (nNewBits > nLastBits * 4)
        nNewBits = nLastBits * 4;
    if (nNewBits < nLastBits / 4)
        nNewBits = nLastBits / 4;
    
    // Clamp the difficulty target to the maximum value
    if (nNewBits > consensusParams.nPowLimit)
        nNewBits = consensusParams.nPowLimit;
    
    return static_cast<uint32_t>(nNewBits);
}

2. To require a higher difficulty for new blocks, you can modify the nTargetTimespan variable in the GetNextWorkRequired function. This variable determines the ideal time between blocks and is currently set to 10 minutes (600 seconds) multiplied by the block height. To require a higher difficulty, you can increase the nTargetTimespan variable to a higher value, such as 15 minutes (900 seconds) multiplied by the block height.

Here is the modified code for the GetNextWorkRequired function:

uint32_t GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader* pblock, const Consensus::Params& consensusParams) {
    // Get the last block's difficulty target
    uint32_t nLastBits = pindexLast->nBits;
    
    // Calculate the time between the last block and the previous block
    int64_t nActualTimespan = pindexLast->GetBlockTime() - pindexLast->pprev->GetBlockTime;

// Calculate the ideal timespan
int64_t nTargetTimespan = consensusParams.nTargetSpacing * (pindexLast->nHeight + 1) * 1.5; // require 1.5x higher difficulty

// Adjust the difficulty target based on the actual timespan and the ideal timespan
int64_t nNewBits = nLastBits;
nNewBits *= nActualTimespan;
nNewBits /= nTargetTimespan;

// Limit the difficulty adjustment to a factor of 4x or 0.25x
if (nNewBits > nLastBits * 4)
    nNewBits = nLastBits * 4;
if (nNewBits < nLastBits / 4)
    nNewBits = nLastBits / 4;

// Clamp the difficulty target to the maximum value
if (nNewBits > consensusParams.nPowLimit)
    nNewBits = consensusParams.nPowLimit;

return static_cast<uint32_t>(nNewBits);
}

In this modified code, we have increased the nTargetTimespan variable to 15 minutes multiplied by the block height and multiplied it by 1.5 to require 1.5x higher difficulty for new blocks.

3. Once you have modified the GetNextWorkRequired function, you will need to recompile the Core Code to apply the changes. You can do this using the standard compilation process for your platform.

4. After recompiling the Core Code, you will need to deploy the modified version of the Bitcoin software on your network. It is essential to thoroughly test the modified software to ensure that it works correctly and does not introduce any security vulnerabilities or other issues.

By following these steps, you can modify the block validation rules in the Core Code of the Bitcoin source code to require a higher difficulty for new blocks. It is important to note that any modifications made to the Core Code must be thoroughly tested and reviewed before being deployed in a production environment. The Bitcoin community has established a rigorous review process for proposed changes to the Core Code, which involves a peer-review process and extensive testing to ensure that the changes do not introduce any security vulnerabilities or other issues.