Thread by @ilblackdragon

It’s exciting to see the Rainbow Bridge launch after a year of development! Bridging tokens, assets, and calling contracts are now possible between Ethereum and NEAR.

Read more: near.org/blog/the-rainb…

Check out the frontend for ERC-20 transfer: ethereum.bridgetonear.org

First I want to thank @k06a who came up with the original design, and to congratulate the group that built Rainbow Bridge with this release: @mzavershynskyi, @ExonumAlex, @mfornet94, @chadoh, Evgeny Kapun, Bo Yao, Alex Kouprin and other members of the team.

Additional thanks to folks across the ecosystem for discussions, reviews, and testing. This was a huge team effort for NEAR, and lots of friends from ETH as well.

Some context and a technical deep-dive on why & how we built the Rainbow Bridge: /thread

We have been building @NEARProtocol, starting from 2018, to be usable and developer-friendly, and we believe it will become the hub for the new crypto-powered creator economy.

(Stay tuned for lots of cool things coming on that front in the next few weeks)

But Ethereum is the starting point of majority of crypto economy and the real center of gravity.

We realized we needed to build connectivity to Ethereum to extend its economy with novel applications. We also wanted to contribute back to Ethereum.

We knew that a bridge to Ethereum needed to be fully decentralized and rely only on the security of the chains it connects.

Any additional security requirements would introduce an extra attack vector – we see this as a major flaw of other cross-chain bridge architectures.

This led to building a bridge based on light client verification. Eth’s light client is generally complex for on-chain verification.

@k06a found a way to reuse work from @KyberNetwork around merkleizing the Ethash DAG to fit it into a smart contract

The same problem existed in the other direction: NEAR’s header verification is too expensive for Ethereum, because ETH doesn’t have an Ed25519 precompile. Currently a specialized optimistic rollup approach is used to verify headers.

In the future, this will be addressed by leveraging either secp256k1 crypto. If Eth1 introduces BLS as precompile, it's also possible to use it.

Either way it will bring the cost of returning assets back to Ethereum from NEAR way down.

Stay tuned for updated designs here.

In spirit, the Rainbow Bridge protocol is similar to IBC. It uses consensus-level security to connect two chains and transmit information. Designed for smart contract chains, Rainbow offers more flexibility to program via extendable connectors and provers.

One interesting way to use the Rainbow Bridge would be to read the state of a user’s account on Ethereum inside NEAR’s contract without any transactions on the Ethereum side.

For example, developers can build a DAO on NEAR, which uses ERC-20 balances on Ethereum as weight for the vote, then this DAO can call into Ethereum's smart contracts to act on the voter's decision.

The Rainbow Bridge protocol is also generic. That means swapping the light client verifier of Ethereum for the light client of another consensus, such as Tendermint-based or GRANDPA-based, will allow the bridge to connect to the Cosmos and Polkadot ecosystems.

We hope the community will be excited to experiment with these and other cool use cases with provers and connectors. Since NEAR is such a fast and cheap smart contract chain, other chains may find it easier to connect to NEAR to use ETH assets than to connect to ETH themselves.

We strongly believe that the near future is multichain and that encouraging interop will provide the best experience for developers and users. The Rainbow Bridge and ERC-20 functionality is step one of many for NEAR’s interop roadmap. Try it and let us know what you think.

/end