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How Rootstock Calculates Secured Hashrate

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Rootstock is secured by Bitcoin miners who merge mine both chains with the same proof of work. The share of Bitcoin's hashpower that does this is measurable. Every participating miner leaves a tag inside the Bitcoin block they mine, so you can count the tagged blocks and scale Bitcoin's total hashrate by that share.

The Rootstock Explorer publishes the result. This page explains each step of the calculation, so anyone can independently verify the published numbers or re-derive them from raw chain data. One framing matters before the math: the metric measures participation, not security directly. It says how much hashpower takes part in merge mining, not what attacking Rootstock would cost.

The published metrics

The Explorer API serves the metrics at GET /api/v3/stats. It exposes four hashrate related fields.

Field	Meaning	Unit
hashrate	Rootstock network hashrate, reported by a Rootstock node	hashes per second, as a string
bitcoinHashrate	Estimated total Bitcoin network hashrate	hashes per second, as a string
mergeMiningPercentage	Share of recent Bitcoin blocks that carry the Rootstock merge-mining tag	ratio between 0 and 1, as a string
rootstockSecuredHashrate	Bitcoin hashpower actively securing Rootstock	hashes per second, as a string

A response looks like this.

{
  "data": {
    "activeAccounts": 112242,
    "hashrate": "608900501771594900000",
    "bitcoinHashrate": "909038172416238900000",
    "rootstockSecuredHashrate": "565421743242900595800",
    "mergeMiningPercentage": "0.622000",
    "circulatingSupply": "1662.234700019254340177",
    "totalSupply": 21000000
  }
}

The two hashrate values are strings because a network hashrate is a 21-digit number, far past the range where a JSON number stays exact. mergeMiningPercentage travels as a string for the same reason, carrying six fixed decimals. The hashrates parse cleanly with JavaScript's built-in BigInt or ethers' BigNumber; the percentage carries decimals, so use an arbitrary-precision decimal library such as bignumber.js or decimal.js.

Step 1: Find the merge-mining tag in a Bitcoin coinbase

Every Bitcoin block starts with a coinbase transaction, which mints the block reward and pays the miner. A merge-mining pool writes a commitment to the Rootstock block it secured into that transaction. The commitment starts with the ASCII string RSKBLOCK:, which is 0x52534b424c4f434b3a in hex, followed by 32 bytes holding the Rootstock block's merged-mining hash.

The merged mining implementation guide documents the exact wire format that pools produce. For measurement you only need to answer one question: do those nine tag bytes appear anywhere in the coinbase?

Bitcoin block 955,501 answers yes. Its coinbase carries an OP_RETURN output holding this script.

6a 29 52534b424c4f434b3a 410ac1c4b7fb2330ffa2b6434afb44429b702189371c4158d102fe13008922b6

Each piece has a job.

• 6a is the OP_RETURN opcode, which marks the output as data rather than spendable value.
• 29 pushes the next 41 bytes.
• 52534b424c4f434b3a is the RSKBLOCK: tag.
• The final 32 bytes are the merged-mining hash of the Rootstock block that this Bitcoin block secured.

Nine tag bytes plus 32 hash bytes make 41, which matches the push opcode. The block is merge mined, and it records a commitment to a specific Rootstock block.

Those 32 bytes are a Rootstock block header hash computed for merged mining, not the block's canonical hash, and eth_getBlockByHash looks blocks up by their canonical hash only. Passing the merged-mining value returns null. The field travels in the other direction: request a block by number or canonical hash and read hashForMergedMining from the response, as the reproduction section below does. Rootstock nodes use it during consensus to verify that the proof of work in this Bitcoin block belongs to that Rootstock block.

Two properties of this check matter for correctness. First, classification depends on tag presence alone. The calculation never looks at Rootstock transactions, so a chain of custody back to Rootstock's own state is not required. Second, the scan covers both places the tag can live. Pools normally use an OP_RETURN output, but the coinbase input script is also valid, and checking only one location undercounts.

Step 2: Count tagged blocks across a window

One block tells you nothing about the network. The Explorer walks back from the Bitcoin tip over the latest 1,000 blocks, roughly seven days, and classifies each one.

mergeMiningPercentage = mergeMinedBlocks / bitcoinBlocksSampled

A 1,000 block window balances two errors. A short window swings wildly when a single large pool pauses for an afternoon. A long window averages in hashpower that stopped merge mining weeks ago. Seven days smooths out pool-level noise while still describing the network as it is today.

The sample size is also the denominator, not a hardcoded 1,000. If some blocks cannot be fetched, the ratio uses the blocks that were actually classified, so a partial sample never reads as a drop in participation.

Step 3: Estimate the total Bitcoin hashrate

Nobody can measure Bitcoin's hashrate directly, because miners do not report how many hashes they tried. It is inferred from two values the network does publish: how hard the mining puzzle is, and how fast blocks arrive.

bitcoinHashrate ≈ difficulty × 2^32 / 600

At difficulty 1 a miner needs about 2^32, or 4.29 billion, attempts to find a block. Scaling by the real difficulty and spreading the work over Bitcoin's 600 second target block time gives hashes per second. Using block 955,501's difficulty of about 1.249 × 10^14, that formula returns roughly 894 EH/s, where one EH/s is 10^18 hashes per second.

That formula is background rather than implementation: it shows what a hashrate estimate means, but it assumes a perfect 600 second block time, which the network never delivers exactly. The Explorer intentionally reads the current network hashrate estimate that a Bitcoin data provider publishes instead, for two reasons. The provider derives its figure from the pace blocks actually arrived at, so it tracks reality more closely when blocks run fast or slow. And a published figure can be re-checked by anyone against the same public source. Read at the same moment, the formula and the provider land within a few percent of each other.

Step 4: Scale the Bitcoin hashrate by the share

The headline metric is a product of the previous two steps.

rootstockSecuredHashrate = bitcoinHashrate × mergeMiningPercentage

The Explorer API's example response in the published metrics shows this product already computed: multiplying bitcoinHashrate (909 EH/s) by mergeMiningPercentage (0.622) gives the 565 EH/s published as rootstockSecuredHashrate. That is close to two thirds of Bitcoin's hashpower protecting a second chain, at no extra energy cost.

The share moves in large steps rather than drifting. Merge mining is a setting that a pool enables once in its poolserver, so a participating pool tags nearly every block it finds and a non-participating pool tags none. Measured over 600 recent blocks, AntPool, F2Pool, ViaBTC, SECPOOL and Luxor tagged 100% of their blocks, while Foundry USA tagged 0% of its 161 blocks. One large pool changing its configuration moves the published metric by several percentage points.

That per-pool split is also a useful check on an independent implementation. Results should be close to all or nothing for each pool, apart from a pool that changed its configuration partway through the window. A detector reporting middling rates for every pool is probably scanning only one of the two tag locations.

How the Explorer produces and serves the numbers

The calculation runs on a schedule rather than on request. A daily job in the Explorer indexer samples the window, computes the three values, and stores one snapshot per day keyed by date. The /api/v3/stats endpoint reads the most recent snapshot, so a request never triggers a walk over 1,000 Bitcoin blocks and response times stay flat.

The daily cadence is deliberate. The metric summarises a seven day window, so it barely moves within a single day, and a faster refresh would repeat a 1,000 block walk to produce the same numbers. One date-keyed row per day also builds a clean historical series for charts, and a re-run on the same day updates that row in place instead of duplicating it.

Three behaviours follow from that design, and they matter if you consume the endpoint.

• The Bitcoin metrics are up to a day old. They describe a seven day window, so they move slowly and a daily refresh is enough resolution.
• The three fields are null until the first snapshot exists. Handle that case rather than assuming a number is always present.
• A snapshot only gets written when the job could classify at least 90% of the window. If a data provider degrades, the job fails and leaves the previous snapshot in place, so the endpoint keeps serving the last good reading instead of a value skewed by missing blocks.

Reproduce the calculation yourself

Four checks take you from the published numbers back to raw chain data.

1. Read the published metrics

Start from the endpoint itself.

curl -s https://be.explorer.rootstock.io/api/v3/stats | jq '.data'

2. Check one Bitcoin block for the tag

The check needs the block's coinbase transaction, and there are two ways to fetch it. The main path uses a Bitcoin RPC provider; a public REST API also works if you have no provider at hand.

With a Bitcoin RPC provider

Any endpoint that speaks the standard Bitcoin JSON-RPC interface works: a hosted provider of your choice or your own node. Replace the placeholder URL with your provider's endpoint.

RPC="https://your-bitcoin-rpc-provider.example/YOUR_API_KEY"

HASH=$(curl -s -X POST "$RPC" -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"getblockhash","params":[955501]}' | jq -r '.result')
TXID=$(curl -s -X POST "$RPC" -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"getblock","params":["'"$HASH"'"]}' | jq -r '.result.tx[0]')
curl -s -X POST "$RPC" -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"getrawtransaction","params":["'"$TXID"'", true, "'"$HASH"'"]}' \
  | jq -r '.result.vin[].coinbase, .result.vout[].scriptPubKey.hex' \
  | grep -i 52534b424c4f434b3a

The three calls resolve the height to a block hash, take the block's first transaction, which is always the coinbase, and decode it. Passing the block hash as the third getrawtransaction argument lets the node locate the transaction without a full transaction index, so the command works on any provider. The jq filter prints the coinbase input script and every output script, and grep keeps the ones carrying the tag.

With a public REST API

The same check runs against a public Esplora compatible API such as mempool.space, with no key required.

HASH=$(curl -s https://mempool.space/api/block-height/955501)
curl -s "https://mempool.space/api/block/$HASH/txs/0" \
  | jq -r '.[0].vin[].scriptsig, .[0].vout[].scriptpubkey' \
  | grep -i 52534b424c4f434b3a

Both paths print the same single line of hex, the OP_RETURN script shown in step 1 without the spacing.

6a2952534b424c4f434b3a410ac1c4b7fb2330ffa2b6434afb44429b702189371c4158d102fe13008922b6

3. Audit the share across a window

Repeat the check across a range of recent heights and divide the number of matches by the number of blocks you checked. Pace your requests: public APIs rate-limit bulk access and hosted provider plans meter request volume; the Explorer's own job waits 250 ms between blocks.

4. Close the loop from the Rootstock side

The diagram in step 1 shows that the payload's last four bytes are a block number, and 0x008922b6 is 8,987,318. Ask a Rootstock node for that block.

curl -s -X POST https://public-node.rsk.co -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"eth_getBlockByNumber","params":["0x8922b6",false]}' \
  | jq -r '.result.hashForMergedMining'

It returns 0x410ac1c4...8922b6, the exact 32 bytes sitting in the Bitcoin coinbase. The same response carries bitcoinMergedMiningHeader, the 80 byte Bitcoin block header whose proof of work seals this Rootstock block. Hash that header twice with SHA-256, reverse the byte order (explorers display block hashes big-endian), and you get Bitcoin block 955,501's hash, which closes the loop: one unit of work, committed on both chains, checkable in both directions.

Reading the numbers

The figures on this page were measured over Bitcoin blocks 958,563 to 959,562, and the single-block walkthrough uses block 955,501. Difficulty, hashrate, and the merge-mining share all drift, so treat every number here as a worked example rather than the current state of the network. Read the endpoint for live values.

Details worth knowing

A few properties of this metric are easy to misread.

• The tag is a commitment, not a full proof. Its presence shows that a miner claimed a Rootstock block. Verifying the claim means checking the merkle proof that links the two blocks, which Rootstock nodes do during consensus. For a participation share, the tag is the correct lightweight signal.
• Testnet reads zero, and that is accurate. Almost no miners embed the tag on Bitcoin testnet, so mergeMiningPercentage there is legitimately 0 and rootstockSecuredHashrate follows it to 0. The bitcoinHashrate value stays non-zero, because testnet still has real hashpower behind it.
• The share is not a security guarantee on its own. It measures how much hashpower participates. The merged mining reference covers the growth phases and the additional protections against double-spend attacks.
• Precision is limited by the inputs. The Bitcoin hashrate is an estimate read to a few significant digits, so the secured hashrate inherits that precision. Comparing two readings to the last digit is not meaningful.