What is Rootstock (RSK)?
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🟢 The simple version
Plain English — no jargon. Start here.
Rootstock (RSK) is an EVM-compatible smart contract sidechain for Bitcoin — secured by Bitcoin miners through merge-mining, using a 2-way peg mechanism where BTC is locked on Bitcoin mainchain and released as RBTC on the Rootstock sidechain, allowing Solidity developers to build applications backed by Bitcoin's mining security.
Bitcoin + EVM: the Rootstock proposition
Rootstock was launched in January 2018 by IOV Labs — one of the earliest attempts to bring Ethereum-style smart contracts to the Bitcoin ecosystem. The fundamental proposition: use Bitcoin's proof-of-work mining to secure an EVM-compatible chain, without requiring any changes to Bitcoin's protocol.
Rootstock is a sidechain — a separate blockchain with its own blocks, transaction history, and state — but connected to Bitcoin via a 2-way peg and secured by Bitcoin miners through merge-mining. Bitcoin miners can simultaneously mine Rootstock blocks at no additional energy cost, giving Rootstock access to a significant fraction of Bitcoin's hashrate for security.
The 2-way peg: BTC ↔ RBTC
RBTC (Smart Bitcoin) is Rootstock's native currency, pegged 1:1 to Bitcoin. To get RBTC, you send BTC to the peg address on Bitcoin mainchain; after a confirmation period, an equivalent amount of RBTC is released on Rootstock. To convert back, you send RBTC to a burn address on Rootstock; after a waiting period, BTC is released on mainchain. The peg ensures RBTC always has the same value as BTC — there is no separate token to speculate on, only wrapped BTC used for gas.
EVM compatibility
Rootstock runs the Ethereum Virtual Machine — Solidity contracts, Hardhat, MetaMask, and standard Ethereum tooling all work on Rootstock with minimal modification. Developers use RBTC instead of ETH for gas. This means the entire Ethereum smart contract ecosystem can deploy on Rootstock, backed by Bitcoin mining security rather than Ethereum's proof-of-stake.
Is it legal in India?
Yes. RBTC is a VDA under Indian law. 30% tax and 1% TDS apply. See India regulation.
🟡 A bit more detail
For when you want to go a little deeper.
Merge-mining on Rootstock
Rootstock uses auxiliary proof-of-work (AuxPoW) merge-mining, identical in mechanism to Syscoin's approach. Bitcoin miners include a Rootstock block header commitment in their Bitcoin coinbase transaction. When the Bitcoin block is mined, the same proof-of-work is submitted to Rootstock. A large fraction of Bitcoin's total hashrate simultaneously mines Rootstock — at times exceeding 50% of Bitcoin's total hashrate, making Rootstock one of the most secured Bitcoin L2s by raw mining power.
Rootstock's DeFi ecosystem includes RSK Swap (Uniswap fork), Sovryn (decentralised lending and trading platform built specifically for BTC), Money on Chain (stablecoin protocol using BTC as collateral), and various other DeFi protocols. Sovryn in particular has attracted users who want to trade and lend BTC without leaving the Bitcoin security model — without wrapping BTC on Ethereum where smart contract risk is higher. Rootstock's long operational history (since 2018) means it has demonstrated real-world resilience.
The Powpeg — trust-minimised peg
Rootstock's 2-way peg uses a system called Powpeg — a multisig managed by "PowPeg functionaries" — hardware security modules (HSMs) that hold the peg keys. The HSMs are configured to only release BTC if they receive a threshold of Rootstock block confirmations and a valid burn transaction on the Rootstock side. The HSMs operate independently of any company — the keys cannot be extracted even by their operators. This hardware-enforced peg is more trust-minimised than a software multisig where keyholders could collude.
Key Rootstock metrics: RBTC in circulation (TVL proxy), merge-mining hashrate percentage (security indicator), DeFi protocol TVL (especially Sovryn), and developer activity. Rootstock competes with Stacks, Liquid Network, and newer Bitcoin L2s. Its EVM compatibility is a major advantage — the largest developer tooling ecosystem already works on Rootstock. Live data: CoinGecko · Rootstock Explorer.
🟣 The full technical picture
For the technically curious.
Rootstock technical architecture
Rootstock runs an EVM node (the RSK Virtual Machine — RVM) that is compatible with the Ethereum Yellow Paper specification. The RVM processes the same opcodes as the EVM but uses Bitcoin-denominated gas (RBTC) and has a faster block time (~30 seconds vs Ethereum's ~12 seconds). Rootstock's block structure includes both the standard transaction set and the merge-mining AuxPoW data. Blocks are produced by merge-mining Bitcoin miners — there is no Rootstock-specific mining hardware required.
Source: Rootstock documentation. dev.rootstock.io · Rootstock whitepaper: rootstock.io/rsk-white-paper-updated.pdf
Gas model and transaction fees
Rootstock uses gas similarly to Ethereum — transactions specify a gas limit and gas price in RBTC. Gas prices on Rootstock are significantly lower than Ethereum mainnet due to lower congestion. The block gas limit is set to accommodate reasonable throughput without exceeding what merge-mining nodes can process. Unlike Ethereum's EIP-1559 fee model, Rootstock uses a simpler fee market model where miners receive the full gas fee. Transaction fees on Rootstock are paid in RBTC (Bitcoin), reinforcing the Bitcoin-native value proposition.
The Powpeg security model: each PowPeg functionary runs a Hardware Security Module (HSM) device that stores the Bitcoin private key for the peg multisig. The HSM firmware is open-source and verifiable. The HSM is programmed to only sign a peg-out transaction (releasing BTC) when it receives: (1) a threshold of block confirmations on Rootstock confirming the RBTC burn transaction, and (2) cryptographic proof that those Rootstock blocks are valid merge-mined blocks from Bitcoin. The HSM checks the merge-mining proof against the current Bitcoin blockchain state. This makes peg-outs trustless with respect to the functionary operators — they cannot steal funds even if compromised, because the HSM hardware enforces the signing conditions independently of software.
Key facts
- Type: Bitcoin sidechain with EVM smart contracts
- Security: Merge-mining with Bitcoin (~50%+ of BTC hashrate)
- Peg: RBTC = BTC 1:1 (Powpeg HSM multisig)
- VM: EVM-compatible (Solidity, Hardhat, MetaMask)
- Block time: ~30 seconds
- Gas token: RBTC (Bitcoin)
- Founded: 2015 (IOV Labs), launched January 2018