UPDATED Treasury Proposal - Open Source EVM+Substrate NFT Bridges

Vision for this proposal

The world is being tokenized and assets of all kinds will soon be tokenized and traded as NFTs. We need a standard and infrastructure to migrate and track the ownership of NFTs across universes (blockchains, parachains, video games, private databases...). We believe in Polkadot's vision of an internet of blockchains, and we want to promote the prosperity of the Polkadot ecosystem. Building the infrastructure to migrate NFTs across universes will help make Polkadot into the center of the NFT world.

Web3 Grant for NFT Migration Protocol

With the support of the web3 Foundation, we have been drafting a protocol for NFT migration in which we have separated the concept of bridge and the concept of relay. This is important because in existing bridges, the relay is integrated and exclusive and what people call “bridge” is usually mostly the “relay” part of the migration infrastructure. In our model, the bridge only acts as an escrow and messaging service, whilst relays are responsible for the state transmission. There can be infinite amounts of relays on a given bridge, and the token creators and token owners can choose which relay they trust to perform the migration if their NFT. Thanks to this architecture, there needs to only be one bridge per universe, and only as many endpoints as the number of universes to migrate to. The bridge itself is fully decentralized and trustless, and anyone is free to create a relay with its own trust mechanism to perform migrations using that bridge. Users don’t need to trust the bridge, only the relay which they can choose.

Scope

As the NFT migration standard is almost complete, we now want to start the work on implementing bridges based on that standard, as well as the tools for others to build bridges. We are asking for help from the Treasury to do that.
These bridges will all be open-source, opinionless and work for any kind of NFTs without restrictions. Our plan is to first implement bridges (modules) for EVM<>EVM migration, because they can be operational already (for example to do a Ropsten<>Ethereum Mainnet migration). Once built, any new bridge built (following the standard) in any universe will be able to migrate NFTs to and from any other existing bridges that follow the standard. We will create a Subrastre module for the bridge so that any parachain using it will be able to receive and send NFTs to and from any universe which has a bridge. We will also do an Ink! implementation of the bridge for chains that do not want to use the substrate module, a web interface, documentation and security audit.

The bridge will follow the specifications and standard of the NFT migration protocol. The exact specifications of the bridge are not yet known as this project is an experiment and exact interface may vary from the current version of the standard.

Full Proposal

https://docs.google.com/document/d/1aoLAW6JjX2LzjDlzs_3I99aq2FcKywjdBv444CxCUu4/edit?usp=sharing