What are Ethereum-compatible smart contracts on the Polkadot parachain?
It’s Moonbeam!
What is Moonbeam?
Moonbeam is a developer-oriented blockchain that strives to provide compatibility with the existing Ethereum developer toolchain and network. It does this by providing a full EVM implementation, a Web3-compatible API, and bridges that connect Moonbeam to existing Ethereum networks. This allows developers to deploy existing Solidity smart contracts and DApp frontends to Moonbeam with minimal changes.
Moonbeam will also be a parachain on the Polkadot network. That means it will get shared security from the Polkadot relay chain and will be able to integrate with other chains that are connected to Polkadot (once that functionality is available on Polkadot).
Our Vision for Moonbeam
We believe in a multi-chain future with many chains, and many users and assets on those chains. In this context, we have created Moonbeam: a smart contract platform that provides an Ethereum-compatible environment for building decentralized applications. Moonbeam was designed to serve these new kinds of assets and users that exist across two or more chains.
Existing smart contract platforms are designed to service the users and assets on a single, specific chain. By providing cross-chain smart contract functionality, Moonbeam allows developers to shift existing workloads and logic to Moonbeam and extend the reach of their applications to new users and assets on other chains.
Moonbeam’s cross-chain integration is accomplished by becoming a parachain on the Polkadot network. The Polkadot network provides integration and connectivity between parachains that are connected to the network and to other non-Polkadot-based chains, such as Ethereum and Bitcoin, via bridges.
Who Benefits From Moonbeam
There are three main audiences who can most benefit from Moonbeam’s cross-chain functionality:
Existing Ethereum-Based Projects
Projects that are struggling with cost and scalability challenges on Ethereum can use Moonbeam to:
- Move portions of their existing workloads and state off of Ethereum Layer 1 with minimal required changes.
- Implement a hybrid approach, where applications live on both Ethereum and Moonbeam simultaneously.
- Extend their reach to the Polkadot network and other chains that are connected to Polkadot.
Polkadot Ecosystem Projects
Ecosystem projects that need smart contract functionality can use Moonbeam to:
- Augment their existing parachains and parathreads.
- Add new functionality that is needed but not included on the main Polkadot relay chain. For example, they could create a place where teams can crowdfund their projects, implement lockdrops, and process other, more complex financial transactions than are provided by base Substrate functionality.
- Leverage the mature and extensive Ethereum development toolchain.
Developers of New DApps
Individuals and teams that want to try building on Polkadot can use Moonbeam to:
- Leverage the specialized functionality from Polkadot parachains while reaching users and assets on other chains.
- Compose functionality from Polkadot parachains by using Moonbeam as a lightweight integration layer that aggregates network services before presenting them to end users. Implementing a composed service using pre-built integrations on a smart contract platform will be a lot faster and easier (in many cases) than building a full Substrate runtime and performing the integrations yourself in the runtime.
Key Features and Functionality
Moonbeam achieves these goals with the following key features:
- Decentralized and Permissionless , providing a base requirement for censorship resistance and support for many existing and future DApp use cases.
- Contains a Full EVM Implementation , enabling Solidity-based smart contracts to be migrated with minimal change and with expected execution results.
- Implements the Web3 RPC API so that existing DApp front-ends can be migrated with minimal change required, and so existing Ethereum-based tools, such as Truffle, Remix, and MetaMask, can be used without modification against Moonbeam.
- Compatible with the Substrate Ecosystem Toolset , including block explorers, front-end development libraries, and wallets, allowing developers and users to use the right tool for what they are trying to accomplish.
- Native Cross-Chain Integration via the Polkadot network and via token bridges, which allows for token movement, state visibility, and message passing with Ethereum and other chains.
- On-Chain Governance to allow stakeholders to quickly and forklessly evolve the base protocol according to developer and community needs.
This unique combination of elements fills a strategic market gap, while allowing Moonbeam to address future developer needs as the Polkadot network grows over time. Building your own chain with Substrate is powerful, but also comes with a number of additional responsibilities, such as learning and implementing the chain’s runtime in Rust, creating a token economy, and incentivizing a community of node operators.
For many developers and projects, an Ethereum-compatible smart contract approach will be much simpler and faster to implement. And by building these smart contracts on Moonbeam, developers can still integrate with other chains and get value from Polkadot-based network effects.
Why We’re Building on Polkadot
After extensive research, we decided to build Moonbeam using the Substrate development framework and to deploy Moonbeam as a parachain on the Polkadot network.
Substrate Blockchain Framework
Substrate is a good technical fit for Moonbeam. By building on top of this framework, we can leverage the extensive functionality that Substrate includes out-of-the-box, rather than building it ourselves. This includes peer-to-peer networking, consensus mechanisms, governance functionality, an EVM implementation, and more.
Overall, using Substrate will dramatically reduce the time and implementation effort needed to implement Moonbeam. Substrate allows a great degree of customization, which is necessary in order to achieve our Ethereum compatibility goals. And, by using Rust, we benefit from both safety guarantees and performance gains.
Polkadot Network and Ecosystem
The Polkadot network is also a good fit for Moonbeam. As a parachain on Polkadot, Moonbeam will be able to directly integrate with — and move tokens between — any other parachains and parathreads on the network.
We can also leverage any of the bridges that are independently built to connect non-Polkadot chains to Polkadot, including bridges to Ethereum. Polkadot’s interoperability model uniquely supports Moonbeam’s cross-chain integration goals and is a key enabling technology to support the Moonbeam vision.
But perhaps just as important as the technical criteria above, we are impressed with the people in the Polkadot ecosystem. This includes individuals at Parity, the Web3 Foundation, and other projects in the ecosystem. We have built many valuable relationships and find the people to be both extremely talented and the kind of people we want to be around.
Ethereum Compatibility
Differences Between Moonbeam and Ethereum
While Moonbeam strives to be compatible with Ethereum’s Web3 API and EVM, there are a number of important Moonbeam differences.
First, Moonbeam uses a Proof of Stake-based consensus mechanism, which means that Proof of Work concepts, such as difficulty, uncles, hashrate, etc., generally don’t have meaning within Moonbeam. For APIs that return values related to Ethereum’s Proof of Work, we return default values. Existing Ethereum contracts that rely on Proof of Work internals (e.g., mining pool contracts) will almost certainly not work as expected on Moonbeam.
Another significant difference between Moonbeam and Ethereum is that Moonbeam includes an extensive set of on-chain governance features based on Substrate functionality. These onchain governance modules include functionality to power upgrades to the blockchain itself based on token weighted voting.
What Stays the Same
If you’re moving portions of your existing workloads and state off of Ethereum Layer 1 to Moonbeam, you can expect minimal required changes (aside from the exceptions noted above). Your applications, contracts, and tools will largely remain unchanged.
Cross-Chain Integration Plans
One of the key planned features for Moonbeam is to provide an easy way for developers to use smart contracts to integrate with other chains in the Polkadot ecosystem.
Polkadot defines a low-level integration protocol, called cross-chain message passing (XCMP), that can be used to facilitate communication between parachains within the Polkadot network and share trusted logic between chains on the Polkadot network, called shared protected runtime execution enclaves (SPREE). Parity is in the process of implementing XCMP and is in the design phase of SPREE as of writing this document (July 2020). Post-Polkadot mainnet launch, XCMP and SPREE support will be released as upgrades to the Polkadot relay chain. We plan to implement and support integration scenarios based on these protocols when they are available.
An Analogy: The “Bash of Polkadot”
For us, Polkadot will serve a similar function to something like Linux. Both are developer-oriented platforms that come with libraries to make building applications easier.
Recall the old Unix philosophy, where users build tools that do one job and do it well. This is similar to the specialization that we expect to happen to parachains on Polkadot. On Linux, you can combine and compose these purpose-built tools together to achieve higher order effects using a shell-like bash. We anticipate Moonbeam-based smart contracts will provide an analogous “bash-like” environment, where specialized smart contracts and parachain functionality can be composed to achieve higher order goals.
It may be the case that projects start as one or more Moonbeam smart contracts and migrate over time to be “native applications” — which could be parathreads or parachains in the Polkadot context — if they need more performance or more direct control over their economies.
Integration with Other Polkadot-Based Chains
The initial scenario we are most interested in is to allow for the movement of tokens from other chains into Moonbeam-based tokens, such that they can be used within DeFi and other applications on the platform. Once their work is done, these assets can then move back or out to other chains.
As the integration features of the Polkadot network evolve, we will continue to provide ways for developers to access those integrations from smart contracts and to compose features across chains in Moonbeam smart contracts.
Integration with Ethereum
Connectivity to Ethereum is an important capability needed for Moonbeam to be able to support Ethereum-based projects, particularly in hybrid deployments where projects are simultaneously deployed to Ethereum and Moonbeam. There is at least one project under development, independent of Moonbeam, to build a parachain-based Ethereum bridge. Once this bridge is operational, it will provide a mechanism for moving tokens, state, and messages to and from Ethereum by leveraging Polkadot.
Until there is a parachain-based bridge in production, we plan to provide two solutions for projects that want to integrate Ethereum and Moonbeam:
- A utility that can export state from Ethereum into a binary file, where this binary file can be used to import that state into Moonbeam. Each use of this utility would be a one-time, one-way migration.
- An integrated point-to-point Ethereum bridge directly incorporated into Moonbeam. This bridge would allow for token movement and cross-chain state queries and messages. As the Polkadot ecosystem develops, we expect multiple Ethereum integration options as choices for projects deploying to Moonbeam.
