erc721

title: Non-Fungible Token Convert between evm and cosmos native nft category: IBC/APP requires: 25, 26,721 kind: instantiation author: uptsmart uptsmart@163.com created: 2022-03-04 modified: 2022-03-06

Abstract

EVM and Cosmos are two different blockchain technologies, and conversion between them involves different protocols and bridging mechanisms. In this case, the conversion from EVM to Cosmos native NFT can realize the transfer of NFT issued on the Ethereum blockchain to the Cosmos blockchain for circulation and transactions. This conversion function can help NFT holders transfer their assets from one blockchain to another for better market liquidity and wider usage scenarios.

When performing this conversion, a corresponding bridge protocol or cross-chain interaction protocol needs to be used to establish the connection between the EVM and the Cosmos blockchain. Once this connection is established, NFT holders can transfer their assets between the two blockchains through specific operations. This conversion function can help expand the coverage of the NFT market, promote cross-chain transactions and interoperability, and improve the liquidity and use value of NFT.

Desired Properties

• Preservation of non-fungibility (i.e., only one instance of any token is live across all the IBC-connected blockchains).
• Permissionless token transfers, no need to whitelist connections, modules, or classIds.
• Symmetric (all chains implement the same logic, no in-protocol differentiation of hubs & zones).

Technical Specification

Data Structures

Convert from cosmos NFT to evm ERC721 asset

// MsgConvertNFT defines a Msg to convert a native Cosmos nft to a ERC721 token
message MsgConvertNFT {
  // nft classID to cnvert to ERC721
  string class_id = 1;
  // nftID to cnvert to ERC721
  repeated string cosmos_token_ids = 2;
  // recipient hex address to receive ERC721 token
  string evm_receiver = 3;
  // cosmos bech32 address from the owner of the given Cosmos coins
  string cosmos_sender = 4;
  // ERC721 token contract address registered in a token pair
  string evm_contract_address = 5;
  // ERC721 token id registered in a token pair
  repeated string evm_token_ids = 6;
}

classId is a required field that MUST never be empty, it uniquely identifies the class/collection/contract which the tokens being transferred belong to in the sending chain. In the case of an ERC-1155 compliant smart contract, for example, this could be a string representation of the top 128 bits of the token ID.

cosmos_token_ids array is a required field that MUST have a size greater than zero and hold non-empty entries that uniquely identify tokens (of the given class) that are being transferred. In the case of an ERC-1155 compliant smart contract, for example, a cosmos_token_ids could be a string representation of the bottom 128 bits of the token ID.

evm_receiver recipient hex address to receive ERC721 token.

evm_contract_address ERC721 token contract address registered in a token pair.

evm_token_ids ERC721 token contract address registered in a token pair.

Convert from evm ERC721 to cosmos NFT asset

// MsgConvertERC721 defines a Msg to convert a ERC721 token to a native Cosmos
// nft.
message MsgConvertERC721 {
    // ERC721 token contract address registered in a token pair
    string evm_contract_address = 1;
    // tokenID to convert
    repeated string evm_token_ids = 2;
    // bech32 address to receive native Cosmos coins
    string cosmos_receiver = 3;
    // sender bech32 address from the owner of the given ERC721 tokens
    string cosmos_sender = 4;
    // nft classID to cnvert to ERC721
    string class_id = 5;
    // nftID to cnvert to ERC721
    repeated string cosmos_token_ids = 6;
}

evm_contract_address ERC721 token contract address registered in a token pair.

evm_token_ids ERC721 token contract address registered in a token pair.

cosmos_receiver bech32 address to receive native Cosmos coins.

cosmos_sender sender bech32 address from the owner of the given ERC721 tokens.

classId is a required field that MUST never be empty, it uniquely identifies the class/collection/contract which the tokens being transferred belong to in the sending chain. In the case of an ERC-1155 compliant smart contract, for example, this could be a string representation of the top 128 bits of the token ID.

cosmos_token_ids array is a required field that MUST have a size greater than zero and hold non-empty entries that uniquely identify tokens (of the given class) that are being transferred. In the case of an ERC-1155 compliant smart contract, for example, a cosmos_token_ids could be a string representation of the bottom 128 bits of the token ID.

related SDK

• Implementation of SDK in nodejs can be found in uptick-chain-sdk.js.

technical documentation

• Related technical documentation can be found in NFT Conversion Document.

Backwards Compatibility

Not applicable.

Copyright

All content herein is licensed under Apache 2.0.