Celer & Rubic: Hidden Cross-Chain DNA

Rubic
9 min readOct 10, 2022

Rubic continues its five-week Anniversary NFT giveaway, where every week is dedicated to a particular Rubic cross-chain provider. Rubic and participating projects are making exclusive and rare NFTs for its users — the ones that will be a key to future benefits and profit. You can find the details of this promotion here. Symbiosis and LI.FI have already given out their top-notch NFTs, so don’t miss this week’s NFT batch –- from Rubic and our beloved partner, one of the main cross-chain providers, Celer Network.

What is the Celer Network and the Celer Inter-chain Message Framework? What is cBridge? How is Celer connected with Rubic? Find the answers right in this article!

Celer Network in the Rubic Ecosystem

Celer is one of the oldest Rubic partners and cross-chain providers. Rubic integrated the Celer Inter-chain Message Framework (Celer IM) on the Ethereum, BNB Chain, Polygon, Avalanche, and Fantom networks with its cBridge as a cross-chain provider in May 2022. The integration of the Celer Inter-chain Message Framework enabled cross-chain swapping on https://app.rubic.exchange in the most cost-efficient way, by improving the rates and increasing its maximum trade volumes.

Since that time, Rubic generated more than $3.7M of cross-chain swap volume to Celer.

We’re pleased to have such a partner as part of Rubic’s ecosystem, and are eager to continue on pushing cross-chain Web3 boundaries. We’re facilitating its mass adoption by uniting our best products and producing the ultimate cross-chain solutions, for businesses and individual users.

What is Celer?

Celer is a blockchain interoperability protocol enabling a one-click user experience accessing tokens, DeFi, GameFi, NFTs, governance, and other multiple chains. Developers can build inter-chain-native dApps using the Celer Inter-chain Message SDK to gain access to efficient liquidity utilization, coherent application logic, and shared states. Users of Celer-enabled dApps will enjoy the benefits of a diverse multi-blockchain ecosystem with the simplicity of a single-transaction UX, all from a single chain.

Celer is comprised of 3 main products that keep Celer’s infrastructure running: The Celer State Guardian Network (SGN), Celer cBridge, and Layer2.finance.

  1. The Celer State Guardian Network (SGN) is a Proof-of-Stake (PoS) blockchain built on Tendermint that serves as the message router between different blockchains. Validator nodes have to stake $CELR tokens to join the consensus process of the SGN. The CELR token is the protocol token for the Celer Network, and the $CELR staking process is a crucial part of the economic security of the Celer Inter-chain Message Framework. To use the SGN’s message routing service and to store the multi-signature attestation, users must pay a fee to the SGN for these services. These usage fees are distributed to the CELR stakers and validators for their work in securing the network to the block reward.

The current number of validators totals 21, with the amount of staked $CELR topping up to 2,456,288,850.

2. Celer cBridge is a decentralized and non-custodial asset bridge that supports 130+ tokens across 30+ blockchains and Layer-2 rollups. Built on top of the Celer Inter-chain Message Framework, cBridge has processed ~$10.8B of cross-chain asset transfer volume on 30+ blockchains for more than 211K unique users, and is quickly growing & expanding into more blockchains and Layer-2s.

Currently, cBridge is one of the core Rubic cross-chain providers that facilitate Rubic’s app, as well as Rubic’s Cross-Chain SDK and Widget for integrating projects.

3. Layer2.finance tackles the two largest challenges preventing DeFi from reaching mass adoption: the extraordinarily high transaction fees, and difficulties in navigation & usage. Layer2.finance is a novel solution allowing crypto market participants to access all existing DeFi protocols at a fraction of the cost by acting as a “DeFi Public Transportation System”.

What is the Celer Inter-chain Message Framework?

Celer Interchain Message Framework (IM) fundamentally changes how multi-blockchain dApps are built and used. Instead of deploying multiple isolated copies of smart contracts on different blockchains, developers can now build inter-chain-native dApps with efficient liquidity utilization, coherent application logic, and shared states. Users of Celer IM-enabled dApps will enjoy the benefits of a diverse multi-blockchain ecosystem with the simplicity of a single-transaction UX, without complicated manual interactions across multiple blockchains.

The Celer IM framework is very easy to use and allows a “plug’n’play” upgrade that often requires no modifications with already-deployed code. As an example, Uniswap and SushiSwap can be transformed into a cross-chain DEX with just a simple plug-in. Rubic is one of the examples that has implemented this functionality as well.

How does the Celer Inter-chain Message Framework function?

Celer uses smart contracts that are deployed on each chain paired with the State Guardian Network, a Tendermint-based blockchain, in order to enable seamless multi-blockchain interoperability.

  1. To send a message or invoke a smart contract function cross-chain, a user or a dApp will first send their intention as a message with a structured header and arbitrary binary payload to a Message Bus smart contract on the source chain.
  2. Then the validator, the State Guardian Network, will first reach a consensus on the existence of such a message and concurrently generate a stake-weighed multi-signature attestation.
  3. This attestation is then relayed to the destination via an Executor subscribing to the message.
  4. On the destination chain, the same Message Bus contract exists to check the validity of the message and triggers the corresponding logic associated with the message, either immediately or after a timeout.

PoS and Optimistic-rollup-like Security Models

Inter-chain dApps built on top of Celer can choose two different security models with different tradeoffs on delay.

By default, inter-chain dApps rely on the security of the State Guardian Network by processing messages routed from another chain without delay. The SGN offers L1-blockchain level security just like Cosmos or Polygon, with it being a Proof-of-Stake (PoS) blockchain built on Tendermint with CELR as the staking asset. If a guardian acts maliciously, its staked CELR will be slashed by the consensus protocol. This level of economic security is something that grows with the staked CELR’s value and is simply not available in simple Multi-signature or MPC-based solutions.

Even under the extreme case of 100% of the guardians behaving maliciously, inter-chain dApps can maintain full security with an optimistic-style delay buffer. Instead of instantly processing a message routed by the SGN, an inter-chain dApp can inject a mandatory delay buffer and run an independent watchtower service to double-validate the message on the source chain. If the watchtower service detects any inconsistency, it can prevent the message being processed before the delay expires.

Celer Inter-Chain Message Design Patterns

Let’s take a step-by-step walkthrough of the architecture of Celer IM and common application design patterns.

On Rubic (and in Rubic’s SDK and widget), cross-chain swaps are executed with a single and simple transaction via Celer, and if, let’s say, a user wants to swap their ETH on Arbitrum to BNB on Binance Smart Chain (BSC), the following happens behind the scenes:

  1. ETH -> USDT on the Arbitrum side via DEX
  2. USDT on Arbitrum is bridged to BSC via cBridge as part of the Celer IM framework
  3. An inter-chain message to execute a USDT->BNB swap is sent to BSC via Celer IM
  4. USDT -> BNB swap on BSC-side DEX is triggered by that remote call on SushiSwap

Cross-chain logic execution with accompanying token transfer

For many inter-chain-native applications, the core flow often involves the process of sending funds to one or more chains, and using those bridged funds to do something on the destination chain(s). You can see this exact pattern in the scheme below. With Celer, most of this flow is handled by Celer IM, so developers only need to work with two simple functions in the framework’s application template.

Step 1: User initiates a transaction to dApp.
Step 2: dApp Plug-in sends a message and associated cross-chain fund transfer.
Step 3: State Guardian Network (SGN) routes the message and cross-chain fund transfer.
Step 4: Executor performs cross-chain application logic.

Cross-chain logic execution without fund transfer

Many applications only need to send cross-chain messages or logic execution instructions without fund transfer. In the NFT marketplace for example, if a user participates in an auction that takes place on a different chain, they will only need to lock up their funds without actually transferring them to the destination chain in order to place a bid. It is only after they win the auction that a fund transfer will be required.

The flow for this would just be a simplified version of the first pattern. The dApp Plugin would only need to implement the logic to call sendMessage on the source chain and then implement the executeMessage function on the destination chain’s dApp Plug-in contract (which is, in Rubic’s case, Rubic’s contract).

Celer: Unlimited, Decentralized, Secure

Celer Network (CELR) is an interoperability platform that supports cross-chain asset transfers and generic message passing. While Celer remains one of the best solutions on the market for developers, allowing them to run an unlimited number of secure, decentralized, high-performance blockchains, it also covers the highly-coveted needs of individual users as well, performing and supporting cross-chain swaps between 37 EVM blockchains with over 900,000 transactions.

Celer Network was created with a specific aim — to turn blockchain technology into mainstream through the increased interoperability and Layer-2 infrastructure on top of blockchain platforms such as Ethereum and Polkadot. Celer’s main goal is to enable cross-chain and multi-chain support for dApp developers and allow fast, secure, and cost-efficient transactions while creating a cryptocurrency economy that incentivizes network participants.

Celer unearths the benefits and erases the limits of cross-chain Web3, and compliments Rubic’s infrastructure with one more sustainable, innovative technology. Moving towards the best ever-present user experience, we’re always pleased to partner with the brightest minds in the blockchain space.

You can stay updated on Celer and its community through the following:

Twitter

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Discord

YouTube

About Rubic

Rubic is a One-Click Cross-Chain Aggregator which allows users to swap any of 15,500+ tokens, on and between 19 blockchains and receive the best rates from all leading trading providers. Rubic includes On-Chain & Cross-Chain swaps for Ethereum, BNB Chain, Polygon, Avalanche, Fantom, Arbitrum, Gnosis, Fuse, Celo, Optimism, Moonbeam, OKC, Boba, Tron, Moonriver, Cronos, and Bitcoin; with seamless fiat on-ramps and more!

Rubic provides the tools for crypto projects to become fully interoperable between blockchains, with an easy-to-install widget and a fully-customizable SDK. Rubic is already servicing more than 90 projects! Installation of Rubic’s SDK or Widget unlocks DeFi for any project, with access to over 15,500+ tokens across 19 blockchains, all available right on your website or inside your app.

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Rubic

Rubic's Best Rate Finder tool for crypto swaps aggregates 70+ blockchains, 220+ DEXs and bridges, and 15,500+ crypto assets.