Getting Started with Rootstock Development
Learn about Rootstock, how it enables smart contract on Bitcoin, and its compatibility with Ethereum and other platforms.
What is Rootstock?
Rootstock is Bitcoin's financial infrastructure. It is an open-source, EVM-compatible Bitcoin sidechain secured by over 85% of Bitcoin's hash power through merge mining. Businesses, financial institutions, and builders use it to launch Bitcoin-secured lending, payments, yield, and treasury products with Ethereum tooling.
The full technology stack runs on that Bitcoin-secured base: from smart contracts on the Rootstock Virtual Machine to services in the Rootstock Infrastructure Framework (RIF). See The Stack.
Rootstock connects to Bitcoin through merged mining and through a shared unit of account. BTC locks in the PowPeg and issues rBTC 1:1 on Rootstock. Rootstock is also compatible with Ethereum at the virtual machine and JSON-RPC layers, so Solidity tooling and familiar wallets work with little change.
Let's briefly look at each of these areas.
PowPeg
The second point of contact is the PowPeg. This component connects both networks to allow the transfer of bitcoins to Rootstock, thereby allowing developers to interact with smart contracts. They pay gas using rBTC, which is pegged 1:1 with BTC.
To do so, you send bitcoin to a special address, where they are locked in the bitcoin network. Next, in the same address over in the Rootstock network, that same bitcoin is released to the user for use in the Rootstock network. This is called peg-in. You can do the reverse operation called peg-out, by sending your bitcoin to a special address in the Rootstock network, and receiving your bitcoin back in the bitcoin network.
Differences with Rootstock and Ethereum
Rootstock is not 100% compatible with Ethereum: It has differences in the way checksums are calculated, the derivation path it uses, and how gas is calculated.
Checksum differences
- Different Ethereum-compatible networks differentiate themselves using “chain IDs”.
- Each blockchain network has its own unique chain ID.
- Rootstock uses the chain ID when calculating checksums for its addresses, whereas Ethereum does not take this into account.
- Checksums in both networks are represented using capitalisation (uppercase and lowercase letters), so the “same” address will not pass checksum validations on both Rootstock and Ethereum.
Derivation path differences
Remembering or storing private keys for your crypto wallets can be super challenging, even for technical people. This is because these keys are essentially extremely large numbers. So to make things easier, the crypto community has come up with a technique called “HD wallets”, where using a seed phrase (a set of randomly chosen dictionary words), plus a “derivation path”. Rootstock and Ethereum have different derivation paths, therefore, the same seed phrase results in a different set of keys and addresses between Rootstock and Ethereum.
Gas differences
The EVM and RVM are compatible in that they support the same op-codes, and therefore can run the same smart contracts. However, the price of each op-code (measured in units known as gas) is different between EVM and RVM, thus the total gas consumed in various transactions is different. Further to that, gas units are multiplied by gas price to calculate the transaction cost. Since Rootstock’s gas price is denominated in rBTC and Ethereum’s gas price is denominated in Ether, there is another difference between gas prices on Rootstock and Ethereum.
We have identified that the opcodes with significant variations are SLOAD and SSTORE.
Additionally, certain calls (such as DELEGATECALL and STATICCALL) that utilize these opcodes during an internal call will result in differences in the overall gas cost calculation for the transaction.
These discrepancies are primarily due to EIP-2929 that has been implemented in Ethereum but not yet in Rootstock. The team is aware of this difference and intend to implement this in future releases.
Eth Estimate Gas Behaviour on Rootstock
When eth_estimateGas is called, the node simulates the transaction execution without broadcasting it to the network.
The simulation runs through the entire transaction process as if it were being executed, including checking for sufficient balance, contract code execution, etc.
During the simulation, the method calculates the exact amount of gas that would be consumed by the transaction if it were to be executed on the blockchain. The estimated gas amount is returned, helping users set an appropriate gas limit for the actual transaction.
Prior to Arrowhead 6.5.0, there was a difference in Rootstock compared to Ethereum:
- If one of the steps of the simulated transaction fails, the node would return the gas estimation needed for the transaction
- On Ethereum, the node would return an error instead of the gas estimation.
Starting with Arrowhead 6.5.0:
- Rootstock will behave same way as Ethereum's behavior for simulated transaction failures.
- If a simulated transaction step fails, the node will now return an error, mirroring Ethereum's response.
This behavior can be seen in the following example, where a call for eth_estimateGas on a transaction that would be executed from an address without enough balance.
Example:
{
"jsonrpc":"2.0",
"method":"eth_estimateGas",
"params":[
{"from": "0xb60e8dd61c5d32be8058bb8eb970870f07233155",
"to": "0xd46e8dd67c5d32be8058bb8eb970870f07244567",
"gas": "0x76c0",
"gasPrice": "0x9184e72a000",
"value": "0x9184e72a",
"data": "0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675"},
"latest"
],
"id":0
}
Response on Rootstock:
{
"jsonrpc": "2.0",
"id": 0,
"result": "0x5498"
}
Response on Ethereum:
{
"jsonrpc": "2.0",
"id": 0,
"error": {
"code": -32000,
"message": "insufficient funds for transfer"
}
}
EVM Compatible Smart Contracts
If you are familiar with smart contract development or dApp development using solidity, web3, and other compatible technologies; you might be excited to know that the Rootstock Virtual Machine (RVM) is compatible with the Ethereum Virtual machine (EVM). So you can use the same code, tools, and libraries when developing with Rootstock too. Thus, the smart contract/dApp development skills that you’re used to will transfer across quite nicely too!
See supported Solidity and EVM versions in requirements and the EVM Compatibility Explorer.
Tools
-
Hardhat is an Ethereum development environment designed for professionals. It's primarily used in the development of smart contracts for the Ethereum blockchain. Refer to the Hardhat Guides for guides on how to use Hardhat on Rootstock.
-
Metamask is a browser extension cryptocurrency wallet or mobile app, enabling users to interact with the Rootstock blockchain, including sending rBTC, sending Rootstock-based tokens such as RIF, and interacting with smart contracts deployed to the Rootstock network. See how to configure MetaMask to connect to Rootstock.
-
Mocha is a popular JavaScript test framework running on Node.js. See Testing Smart Contracts to see how to use it to test your smart contracts on Rootstock.
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Solidity is the most popular programming language for implementing smart contracts. The bytecode and ABI that the Solidity compiler,
solc, outputs can be used to deploy and interact with smart contracts on Rootstock, thanks to the compatibility between RVM and EVM.
For a comprehensive list of tools, see Dev Tools section.
Ethereum Compatible JSON RPC
The set of remote procedure calls (RPCs) that Rootstock supports is largely the same as the RPCs supported by Ethereum. This is another layer of compatibility, in addition to the virtual machine implementation, which allows the same tools and libraries to be used.
Merged Mining
The bitcoin miners do what is known as merged mining, securing both networks with the same infrastructure and energy consumption.
They create blocks on the bitcoin network every 10 minutes, including transfer of bitcoin from different addresses, and in the process they create new bitcoins. On Rootstock, blocks are created every 30 seconds, to secure the execution of smart contracts. This does not mint any new coins in the process, but does earn a reward from the merged mining. Check out rootstock.io/mine-btc-with-rootstock to learn more about mining.
The time between blocks on each network listed above are approximate values.