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Celer cBridge: A High-Speed, Low-Cost Value Transfer Network for a Layer-1 and Layer-2 Connected Future

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Users can transfer value within or between any Ethereum Layer-2 system, Ethereum main chain, and other Layer-1 or Layer-2 through Celer cBridge.

Original title: "Celer cBridge: A High-Speed and Low-Cost Value Transfer Network for a Layer-1 and Layer-2 Connected Future"

< blockquote style="text-align: left;">Original source: Celer

Figure 1 Celer cBridge architecture diagram

We are proud to launch Celer cBridge, a high-speed and low-cost Cross-chain payment network. Users can transfer value within or between any Ethereum Layer-2 system, Ethereum main chain, and other Layer-1 or Layer-2 through the network.

Celer cBridge use cases include

- Fast and low-cost payments between Layer-2 of Ethereum without going through Layer-1. These Layer-2 networks include Optimistic Rollups (such as Optimism, Arbitrum, and Celer Rollup), PoS sidechains (such as Matic and SKALE);

- in Layer-1 Fast asset transfer between Layer-2 and Layer-2 without long delay;

- Realize the main chain without going through the main chain A two-way bridge between Layer-2 and another main chain;

- Seamless connection with Celer state channel network for cross-chain routing.

Why is cBridge important?

We are moving towards a multi-chain era. More and more distributed applications and digital assets are deployed in various weakly coupled systems. These systems have different trade-offs between safety, throughput, latency, ease of development, and modularity. They include different Layer-1s (e.g. Ethereum, Cosmos, Polkadot), shards of these Layer-1s, and different Layer-2 scaling solutions (e.g. Optimistic Rollup, ZK Rollup, and sidechains).

Even if the operations and transactions within the respective systems are relatively smooth, cross-chain transactions or asset transfers are often expensive and slow. Taking rollup as an example, it usually takes several days to transfer assets out of the rollup main chain contract, and the payment transfer between different rollups is more time-consuming and laborious.

In order to allow funds to flow efficiently between different systems without long delays or trust-based custodians, a Parallel chains and a common value network that flattens different layer systems are particularly important.

cBridge Demo: https://www.youtube.com/watch?v=wX75Z-4MEoM&feature=emb_rel_pause

cBridge is such a universal value network. As shown in Figure 1, a customer on Arbitrum can pay to a customer on Polkadot through the multi-hop cBridge and Celer state channel network, passing through the Arbitrum cBridge, to multiple state channel nodes on the Ethereum main network, and finally to the Polkadot node. This process only requires millisecond-level delay and extremely low cost.

To further compare the performance improvement, we can see that it takes half a month to do the above operation without cBridge, Latency up to a million times that of cBridge. In terms of cost, cBridge has the low cost of state channels instead of transaction fees. Its fees are related to the total amount transferred and its liquidity funds. This will reduce the cost of small asset transfers hundreds of times. Obviously, cBridge plays an extremely important role in the unified high-speed asset transfer of users within and between different networks.

How does cBridge work?

As shown in Figure 1, we implement cBridge by extending the Celer state channel, enhancing the existing protocol so that it can run on multiple chains simultaneously. For example, A in Figure 1 can exist in Optimism rollup, Arbitrum rollup, Celer rollup, and Ethereum mainnet at the same time. Node A connects all customers who want to bridge funds between the four chains, and also provides liquidity for asset bridging between Layer-2 and Layer-1. These multi-dwelling nodes (such as A) can be connected to different state channel main networks, and the connections between these multi-dwelling nodes constitute the "backbone network" of this cross-chain network.

Figure 2 Celer cross Simplified example of chain payment

Figure 2 shows a multi-hop chain-1 node A to chain-3 node D Example of chain payment. These different chains can be any EVM compatible platform, such as Aritrum/Optimism rollup, side chains, eth2 shards, or other layer-1 main chains. Intermediate nodes (B and C) provide state channel liquidity and payment forwarding services to end customers (A and D). In the above example, B runs one node each on chain-1 and chain-2 at the same time, and C runs one node each on chain-2 and chain-3 at the same time.

If all nodes cooperate honestly, the cross-chain payment will be settled quickly and instantly. If any node along the way does not cooperate or do evil, other nodes can force settlement in the CelerPay contract on the chain, thus ensuring the fund security of all honest nodes. Our online architecture document details the CelerPay contract and payment protocol on a single chain. In order to realize cross-chain payment on a multi-chain platform, we need to deploy contracts on each chain, add a chain-id identifier to the payment address, and add a payment conversion protocol when crossing chains. In the example above, payAD, payAD*, and payAD** have the same sending and receiving addresses, payment value, hash lock, and different local tokens and contract addresses. Intermediate nodes B and C are responsible for payment conversion when crossing chains.

How is cBridge different?

cBridge is a Celer-based state channel product that has been battle-tested in game applications with millions of users. Other solutions include some cross-chain bridging contracts, and other Layer-2 bridging systems (such as Vector implemented by our partner Connext). The following table compares the characteristics of these systems.

How to use cBridge?

Celer state channel network has added the function of state channel cross-chain payment. To test this function, you need to deploy the CelerPay contract on each EVM test chain, or deploy the corresponding contract or plug-in on a non-EVM compatible chain (such as the Celer Substrate module on Polkadot). In addition, the cBridge operator needs to start a node on each chain, and use the command line tool we provide to write the information configuration (example) required for cross-chain payment into the corresponding node database. The local end-to-end test in the code can be used as an example to some extent to demonstrate the fast state channel payment across the three chains (Figure 2).

Celer cBridge is ready for immediate production without any CelerPay contract changes. With the further popularization of Layer-2, we will provide a friendly web interface to the majority of users in the future.