<p>BIP34Height and BIP34Hash are just the historical height and block hash at which BIP34 activated.</p>

<p>They are an optimization. Earlier versions of the code implemented the exact rules from the BIP34, checking whether the transition criteria were satisfied for every block. This was relatively expensive, and as BIP34's activation is a long time ago now, that check has been replaced with a simpler one that just looks at height and hash of the chain at a certain height.</p>

<p>If you create a new chain from scratch, you can just set this to 0/genesis to have BIP34 be active from the start.</p>

CC BY-SA 3.0
2017-06-14T17:02:10.867Z
2017-06-14T17:02:10.867Z
Pieter Wuille
<p>I know this going to be a repeat question, however I am still puzzled with the implementation of the BIP34 especially where it come to its hash.</p>

<p>Referring to the chainparams.cpp at github :</p>

<p><a href="https://github.com/bitcoin/bitcoin/blob/master/src/chainparams.cpp" rel="nofollow noreferrer">https://github.com/bitcoin/bitcoin/blob/master/src/chainparams.cpp</a></p>

<pre><code>static CBlock CreateGenesisBlock(const char* pszTimestamp, const CScript&amp; genesisOutputScript, uint32_t nTime, uint32_t nNonce, uint32_t nBits, int32_t nVersion, const CAmount&amp; genesisReward)
{
    CMutableTransaction txNew;
    txNew.nVersion = 1;
    txNew.vin.resize(1);
    txNew.vout.resize(1);
    txNew.vin[0].scriptSig = CScript() &lt;&lt; 486604799 &lt;&lt; CScriptNum(4) &lt;&lt; std::vector&lt;unsigned char&gt;((const unsigned char*)pszTimestamp, (const unsigned char*)pszTimestamp + strlen(pszTimestamp));
    txNew.vout[0].nValue = genesisReward;
    txNew.vout[0].scriptPubKey = genesisOutputScript;

    CBlock genesis;
    genesis.nTime    = nTime;
    genesis.nBits    = nBits;
    genesis.nNonce   = nNonce;
    genesis.nVersion = nVersion;
    genesis.vtx.push_back(MakeTransactionRef(std::move(txNew)));
    genesis.hashPrevBlock.SetNull();
    genesis.hashMerkleRoot = BlockMerkleRoot(genesis);
    return genesis;
}

/**
 * Build the genesis block. Note that the output of its generation
 * transaction cannot be spent since it did not originally exist in the
 * database.
 *
 * CBlock(hash=000000000019d6, ver=1, hashPrevBlock=00000000000000, hashMerkleRoot=4a5e1e, nTime=1231006505, nBits=1d00ffff, nNonce=2083236893, vtx=1)
 *   CTransaction(hash=4a5e1e, ver=1, vin.size=1, vout.size=1, nLockTime=0)
 *     CTxIn(COutPoint(000000, -1), coinbase 04ffff001d0104455468652054696d65732030332f4a616e2f32303039204368616e63656c6c6f72206f6e206272696e6b206f66207365636f6e64206261696c6f757420666f722062616e6b73)
 *     CTxOut(nValue=50.00000000, scriptPubKey=0x5F1DF16B2B704C8A578D0B)
 *   vMerkleTree: 4a5e1e
 */

static CBlock CreateGenesisBlock(uint32_t nTime, uint32_t nNonce, uint32_t     nBits, int32_t nVersion, const CAmount&amp; genesisReward)
{
    const char* pszTimestamp = "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks";
    const CScript genesisOutputScript = CScript() &lt;&lt; ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f") &lt;&lt; OP_CHECKSIG;
    return CreateGenesisBlock(pszTimestamp, genesisOutputScript, nTime, nNonce, nBits, nVersion, genesisReward);
}

void CChainParams::UpdateVersionBitsParameters(Consensus::DeploymentPos d, int64_t nStartTime, int64_t nTimeout)
{
    consensus.vDeployments[d].nStartTime = nStartTime;
    consensus.vDeployments[d].nTimeout = nTimeout;
}

/**
 * Main network
 */
/**
 * What makes a good checkpoint block?
 * + Is surrounded by blocks with reasonable timestamps
 *   (no blocks before with a timestamp after, none after with
 *    timestamp before)
 * + Contains no strange transactions
 */

class CMainParams : public CChainParams {
public:
    CMainParams() {
    strNetworkID = "main";
    consensus.nSubsidyHalvingInterval = 210000;
    consensus.BIP34Height = 227931;
    consensus.BIP34Hash = uint256S("0x000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8");
    consensus.BIP65Height = 388381; // 000000000000000004c2b624ed5d7756c508d90fd0da2c7c679febfa6c4735f0
    consensus.BIP66Height = 363725; // 00000000000000000379eaa19dce8c9b722d46ae6a57c2f1a988119488b50931
    consensus.powLimit = uint256S("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
    consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
    consensus.nPowTargetSpacing = 10 * 60;
    consensus.fPowAllowMinDifficultyBlocks = false;
    consensus.fPowNoRetargeting = false;
    consensus.nRuleChangeActivationThreshold = 1916; // 95% of 2016
    consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
    consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
    consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 1199145601; // January 1, 2008
    consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = 1230767999; // December 31, 2008

    // Deployment of BIP68, BIP112, and BIP113.
    consensus.vDeployments[Consensus::DEPLOYMENT_CSV].bit = 0;
    consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 1462060800; // May 1st, 2016
    consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 1493596800; // May 1st, 2017

    // Deployment of SegWit (BIP141, BIP143, and BIP147)
    consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].bit = 1;
    consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nStartTime = 1479168000; // November 15th, 2016.
    consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout = 1510704000; // November 15th, 2017.

    // The best chain should have at least this much work.
    consensus.nMinimumChainWork = uint256S("0x0000000000000000000000000000000000000000003f94d1ad391682fe038bf5");

    // By default assume that the signatures in ancestors of this block are valid.
    consensus.defaultAssumeValid = uint256S("0x00000000000000000013176bf8d7dfeab4e1db31dc93bc311b436e82ab226b90"); //453354

    /**
     * The message start string is designed to be unlikely to occur in normal data.
     * The characters are rarely used upper ASCII, not valid as UTF-8, and produce
     * a large 32-bit integer with any alignment.
     */
    pchMessageStart[0] = 0xf9;
    pchMessageStart[1] = 0xbe;
    pchMessageStart[2] = 0xb4;
    pchMessageStart[3] = 0xd9;
    nDefaultPort = 8333;
    nPruneAfterHeight = 100000;

    genesis = CreateGenesisBlock(1231006505, 2083236893, 0x1d00ffff, 1, 50 * COIN);
    consensus.hashGenesisBlock = genesis.GetHash();
    assert(consensus.hashGenesisBlock == uint256S("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"));
    assert(genesis.hashMerkleRoot == uint256S("0x4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"));

    // Note that of those with the service bits flag, most only support a subset of possible options
    vSeeds.push_back(CDNSSeedData("bitcoin.sipa.be", "seed.bitcoin.sipa.be", true)); // Pieter Wuille, only supports x1, x5, x9, and xd
    vSeeds.push_back(CDNSSeedData("bluematt.me", "dnsseed.bluematt.me", true)); // Matt Corallo, only supports x9
    vSeeds.push_back(CDNSSeedData("dashjr.org", "dnsseed.bitcoin.dashjr.org")); // Luke Dashjr
    vSeeds.push_back(CDNSSeedData("bitcoinstats.com", "seed.bitcoinstats.com", true)); // Christian Decker, supports x1 - xf
    vSeeds.push_back(CDNSSeedData("bitcoin.jonasschnelli.ch", "seed.bitcoin.jonasschnelli.ch", true)); // Jonas Schnelli, only supports x1, x5, x9, and xd
    vSeeds.push_back(CDNSSeedData("petertodd.org", "seed.btc.petertodd.org", true)); // Peter Todd, only supports x1, x5, x9, and xd

    base58Prefixes[PUBKEY_ADDRESS] = std::vector&lt;unsigned char&gt;(1,0);
    base58Prefixes[SCRIPT_ADDRESS] = std::vector&lt;unsigned char&gt;(1,5);
    base58Prefixes[SECRET_KEY] =     std::vector&lt;unsigned char&gt;(1,128);
    base58Prefixes[EXT_PUBLIC_KEY] = boost::assign::list_of(0x04)(0x88)(0xB2)(0x1E).convert_to_container&lt;std::vector&lt;unsigned char&gt; &gt;();
    base58Prefixes[EXT_SECRET_KEY] = boost::assign::list_of(0x04)(0x88)(0xAD)(0xE4).convert_to_container&lt;std::vector&lt;unsigned char&gt; &gt;();

    vFixedSeeds = std::vector&lt;SeedSpec6&gt;(pnSeed6_main, pnSeed6_main + ARRAYLEN(pnSeed6_main));

    fDefaultConsistencyChecks = false;
    fRequireStandard = true;
    fMineBlocksOnDemand = false;

    checkpointData = (CCheckpointData) {
        boost::assign::map_list_of
        ( 11111, uint256S("0x0000000069e244f73d78e8fd29ba2fd2ed618bd6fa2ee92559f542fdb26e7c1d"))
        ( 33333, uint256S("0x000000002dd5588a74784eaa7ab0507a18ad16a236e7b1ce69f00d7ddfb5d0a6"))
        ( 74000, uint256S("0x0000000000573993a3c9e41ce34471c079dcf5f52a0e824a81e7f953b8661a20"))
        (105000, uint256S("0x00000000000291ce28027faea320c8d2b054b2e0fe44a773f3eefb151d6bdc97"))
        (134444, uint256S("0x00000000000005b12ffd4cd315cd34ffd4a594f430ac814c91184a0d42d2b0fe"))
        (168000, uint256S("0x000000000000099e61ea72015e79632f216fe6cb33d7899acb35b75c8303b763"))
        (193000, uint256S("0x000000000000059f452a5f7340de6682a977387c17010ff6e6c3bd83ca8b1317"))
        (210000, uint256S("0x000000000000048b95347e83192f69cf0366076336c639f9b7228e9ba171342e"))
        (216116, uint256S("0x00000000000001b4f4b433e81ee46494af945cf96014816a4e2370f11b23df4e"))
        (225430, uint256S("0x00000000000001c108384350f74090433e7fcf79a606b8e797f065b130575932"))
        (250000, uint256S("0x000000000000003887df1f29024b06fc2200b55f8af8f35453d7be294df2d214"))
        (279000, uint256S("0x0000000000000001ae8c72a0b0c301f67e3afca10e819efa9041e458e9bd7e40"))
        (295000, uint256S("0x00000000000000004d9b4ef50f0f9d686fd69db2e03af35a100370c64632a983"))
    };

    chainTxData = ChainTxData{
        // Data as of block 00000000000000000166d612d5595e2b1cd88d71d695fc580af64d8da8658c23 (height 446482).
        1483472411, // * UNIX timestamp of last known number of transactions
        184495391,  // * total number of transactions between genesis and that timestamp
                    //   (the tx=... number in the SetBestChain debug.log lines)
        3.2         // * estimated number of transactions per second after that timestamp
    };
    }
};
</code></pre>

<p>consensus.BIP34Hash = uint256S("0x000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8")</p>

<p>How to you guys manage to generate the hash for BIP34?</p>

<p>On the other hand, referring to BIP34 wiki at:</p>

<p><a href="https://github.com/bitcoin/bips/blob/master/bip-0034.mediawiki" rel="nofollow noreferrer">https://github.com/bitcoin/bips/blob/master/bip-0034.mediawiki</a></p>

<p>Specification:</p>

<pre><code>1.Treat transactions with a version greater than 1 as non-standard (official Satoshi client will not mine or relay them).

2.Add height as the first item in the coinbase transaction's scriptSig, and increase block version to 2. The format of the height is "serialized CScript" -- first byte is number of bytes in the number (will be 0x03 on main net for the next 300 or so years), following bytes are little-endian representation of the number.

3.If 75% of the last 1,000 blocks are version 2 or greater, reject invalid version 2 blocks. (testnet3: 51 of last 100)

4."Point of no return" If 95% of the last 1,000 blocks are version 2 or greater, reject all version 1 blocks. (testnet3: 75 of last 100)
</code></pre>

<p>Can you guys come of with the formula or example? plus, how was the consensus.BIP34Height function and being generated?</p>

<p>Thanks</p>

<bitcoin-core-development><consensus><bip-34>
How to calculate the BIP34Hash?
dragon
# How to calculate the BIP34Hash?

(Asked by: username_0 on 2017-06-07)

I know this going to be a repeat question, however I am still puzzled with the implementation of the BIP34 especially where it come to its hash.

Referring to the chainparams.cpp at github :

<https://github.com/bitcoin/bitcoin/blob/master/src/chainparams.cpp>

```
static CBlock CreateGenesisBlock(const char* pszTimestamp, const CScript& genesisOutputScript, uint32_t nTime, uint32_t nNonce, uint32_t nBits, int32_t nVersion, const CAmount& genesisReward)
{
    CMutableTransaction txNew;
    txNew.nVersion = 1;
    txNew.vin.resize(1);
    txNew.vout.resize(1);
    txNew.vin[0].scriptSig = CScript() << 486604799 << CScriptNum(4) << std::vector<unsigned char>((const unsigned char*)pszTimestamp, (const unsigned char*)pszTimestamp + strlen(pszTimestamp));
    txNew.vout[0].nValue = genesisReward;
    txNew.vout[0].scriptPubKey = genesisOutputScript;

    CBlock genesis;
    genesis.nTime    = nTime;
    genesis.nBits    = nBits;
    genesis.nNonce   = nNonce;
    genesis.nVersion = nVersion;
    genesis.vtx.push_back(MakeTransactionRef(std::move(txNew)));
    genesis.hashPrevBlock.SetNull();
    genesis.hashMerkleRoot = BlockMerkleRoot(genesis);
    return genesis;
}

/**
 * Build the genesis block. Note that the output of its generation
 * transaction cannot be spent since it did not originally exist in the
 * database.
 *
 * CBlock(hash=000000000019d6, ver=1, hashPrevBlock=00000000000000, hashMerkleRoot=4a5e1e, nTime=1231006505, nBits=1d00ffff, nNonce=2083236893, vtx=1)
 *   CTransaction(hash=4a5e1e, ver=1, vin.size=1, vout.size=1, nLockTime=0)
 *     CTxIn(COutPoint(000000, -1), coinbase 04ffff001d0104455468652054696d65732030332f4a616e2f32303039204368616e63656c6c6f72206f6e206272696e6b206f66207365636f6e64206261696c6f757420666f722062616e6b73)
 *     CTxOut(nValue=50.00000000, scriptPubKey=0x5F1DF16B2B704C8A578D0B)
 *   vMerkleTree: 4a5e1e
 */

static CBlock CreateGenesisBlock(uint32_t nTime, uint32_t nNonce, uint32_t     nBits, int32_t nVersion, const CAmount& genesisReward)
{
    const char* pszTimestamp = "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks";
    const CScript genesisOutputScript = CScript() << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f") << OP_CHECKSIG;
    return CreateGenesisBlock(pszTimestamp, genesisOutputScript, nTime, nNonce, nBits, nVersion, genesisReward);
}

void CChainParams::UpdateVersionBitsParameters(Consensus::DeploymentPos d, int64_t nStartTime, int64_t nTimeout)
{
    consensus.vDeployments[d].nStartTime = nStartTime;
    consensus.vDeployments[d].nTimeout = nTimeout;
}

/**
 * Main network
 */
/**
 * What makes a good checkpoint block?
 * + Is surrounded by blocks with reasonable timestamps
 *   (no blocks before with a timestamp after, none after with
 *    timestamp before)
 * + Contains no strange transactions
 */

class CMainParams : public CChainParams {
public:
    CMainParams() {
    strNetworkID = "main";
    consensus.nSubsidyHalvingInterval = 210000;
    consensus.BIP34Height = 227931;
    consensus.BIP34Hash = uint256S("0x000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8");
    consensus.BIP65Height = 388381; // 000000000000000004c2b624ed5d7756c508d90fd0da2c7c679febfa6c4735f0
    consensus.BIP66Height = 363725; // 00000000000000000379eaa19dce8c9b722d46ae6a57c2f1a988119488b50931
    consensus.powLimit = uint256S("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
    consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
    consensus.nPowTargetSpacing = 10 * 60;
    consensus.fPowAllowMinDifficultyBlocks = false;
    consensus.fPowNoRetargeting = false;
    consensus.nRuleChangeActivationThreshold = 1916; // 95% of 2016
    consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
    consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
    consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 1199145601; // January 1, 2008
    consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = 1230767999; // December 31, 2008

    // Deployment of BIP68, BIP112, and BIP113.
    consensus.vDeployments[Consensus::DEPLOYMENT_CSV].bit = 0;
    consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 1462060800; // May 1st, 2016
    consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 1493596800; // May 1st, 2017

    // Deployment of SegWit (BIP141, BIP143, and BIP147)
    consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].bit = 1;
    consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nStartTime = 1479168000; // November 15th, 2016.
    consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout = 1510704000; // November 15th, 2017.

    // The best chain should have at least this much work.
    consensus.nMinimumChainWork = uint256S("0x0000000000000000000000000000000000000000003f94d1ad391682fe038bf5");

    // By default assume that the signatures in ancestors of this block are valid.
    consensus.defaultAssumeValid = uint256S("0x00000000000000000013176bf8d7dfeab4e1db31dc93bc311b436e82ab226b90"); //453354

    /**
     * The message start string is designed to be unlikely to occur in normal data.
     * The characters are rarely used upper ASCII, not valid as UTF-8, and produce
     * a large 32-bit integer with any alignment.
     */
    pchMessageStart[0] = 0xf9;
    pchMessageStart[1] = 0xbe;
    pchMessageStart[2] = 0xb4;
    pchMessageStart[3] = 0xd9;
    nDefaultPort = 8333;
    nPruneAfterHeight = 100000;

    genesis = CreateGenesisBlock(1231006505, 2083236893, 0x1d00ffff, 1, 50 * COIN);
    consensus.hashGenesisBlock = genesis.GetHash();
    assert(consensus.hashGenesisBlock == uint256S("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"));
    assert(genesis.hashMerkleRoot == uint256S("0x4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"));

    // Note that of those with the service bits flag, most only support a subset of possible options
    vSeeds.push_back(CDNSSeedData("bitcoin.sipa.be", "seed.bitcoin.sipa.be", true)); // username_1 username_1, only supports x1, x5, x9, and xd
    vSeeds.push_back(CDNSSeedData("bluematt.me", "dnsseed.bluematt.me", true)); // Matt Corallo, only supports x9
    vSeeds.push_back(CDNSSeedData("dashjr.org", "dnsseed.bitcoin.dashjr.org")); // Luke Dashjr
    vSeeds.push_back(CDNSSeedData("bitcoinstats.com", "seed.bitcoinstats.com", true)); // Christian Decker, supports x1 - xf
    vSeeds.push_back(CDNSSeedData("bitcoin.jonasschnelli.ch", "seed.bitcoin.jonasschnelli.ch", true)); // Jonas Schnelli, only supports x1, x5, x9, and xd
    vSeeds.push_back(CDNSSeedData("petertodd.org", "seed.btc.petertodd.org", true)); // Peter Todd, only supports x1, x5, x9, and xd

    base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,0);
    base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,5);
    base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,128);
    base58Prefixes[EXT_PUBLIC_KEY] = boost::assign::list_of(0x04)(0x88)(0xB2)(0x1E).convert_to_container<std::vector<unsigned char> >();
    base58Prefixes[EXT_SECRET_KEY] = boost::assign::list_of(0x04)(0x88)(0xAD)(0xE4).convert_to_container<std::vector<unsigned char> >();

    vFixedSeeds = std::vector<SeedSpec6>(pnSeed6_main, pnSeed6_main + ARRAYLEN(pnSeed6_main));

    fDefaultConsistencyChecks = false;
    fRequireStandard = true;
    fMineBlocksOnDemand = false;

    checkpointData = (CCheckpointData) {
        boost::assign::map_list_of
        ( 11111, uint256S("0x0000000069e244f73d78e8fd29ba2fd2ed618bd6fa2ee92559f542fdb26e7c1d"))
        ( 33333, uint256S("0x000000002dd5588a74784eaa7ab0507a18ad16a236e7b1ce69f00d7ddfb5d0a6"))
        ( 74000, uint256S("0x0000000000573993a3c9e41ce34471c079dcf5f52a0e824a81e7f953b8661a20"))
        (105000, uint256S("0x00000000000291ce28027faea320c8d2b054b2e0fe44a773f3eefb151d6bdc97"))
        (134444, uint256S("0x00000000000005b12ffd4cd315cd34ffd4a594f430ac814c91184a0d42d2b0fe"))
        (168000, uint256S("0x000000000000099e61ea72015e79632f216fe6cb33d7899acb35b75c8303b763"))
        (193000, uint256S("0x000000000000059f452a5f7340de6682a977387c17010ff6e6c3bd83ca8b1317"))
        (210000, uint256S("0x000000000000048b95347e83192f69cf0366076336c639f9b7228e9ba171342e"))
        (216116, uint256S("0x00000000000001b4f4b433e81ee46494af945cf96014816a4e2370f11b23df4e"))
        (225430, uint256S("0x00000000000001c108384350f74090433e7fcf79a606b8e797f065b130575932"))
        (250000, uint256S("0x000000000000003887df1f29024b06fc2200b55f8af8f35453d7be294df2d214"))
        (279000, uint256S("0x0000000000000001ae8c72a0b0c301f67e3afca10e819efa9041e458e9bd7e40"))
        (295000, uint256S("0x00000000000000004d9b4ef50f0f9d686fd69db2e03af35a100370c64632a983"))
    };

    chainTxData = ChainTxData{
        // Data as of block 00000000000000000166d612d5595e2b1cd88d71d695fc580af64d8da8658c23 (height 446482).
        1483472411, // * UNIX timestamp of last known number of transactions
        184495391,  // * total number of transactions between genesis and that timestamp
                    //   (the tx=... number in the SetBestChain debug.log lines)
        3.2         // * estimated number of transactions per second after that timestamp
    };
    }
};

```

consensus.BIP34Hash = uint256S("0x000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8")

How to you guys manage to generate the hash for BIP34?

On the other hand, referring to BIP34 wiki at:

<https://github.com/bitcoin/bips/blob/master/bip-0034.mediawiki>

Specification:

```
1.Treat transactions with a version greater than 1 as non-standard (official Satoshi client will not mine or relay them).

2.Add height as the first item in the coinbase transaction's scriptSig, and increase block version to 2. The format of the height is "serialized CScript" -- first byte is number of bytes in the number (will be 0x03 on main net for the next 300 or so years), following bytes are little-endian representation of the number.

3.If 75% of the last 1,000 blocks are version 2 or greater, reject invalid version 2 blocks. (testnet3: 51 of last 100)

4."Point of no return" If 95% of the last 1,000 blocks are version 2 or greater, reject all version 1 blocks. (testnet3: 75 of last 100)

```

Can you guys come of with the formula or example? plus, how was the consensus.BIP34Height function and being generated?

Thanks

**Tags:** bitcoin-core-development, consensus, bip-34


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## 1 answers

### Answer by username_1 on 2017-06-14. Score: 4 | Accepted answer

BIP34Height and BIP34Hash are just the historical height and block hash at which BIP34 activated.

They are an optimization. Earlier versions of the code implemented the exact rules from the BIP34, checking whether the transition criteria were satisfied for every block. This was relatively expensive, and as BIP34's activation is a long time ago now, that check has been replaced with a simpler one that just looks at height and hash of the chain at a certain height.

If you create a new chain from scratch, you can just set this to 0/genesis to have BIP34 be active from the start.


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