As a solution of rToken proposed by StaFi, rToken protocol is an extensible cross-chain communication protocol between StaFi chain and other foreign chains such like Polkadot, Cosmos, Solana, etc. rToken protocol mainly consists two parts, one is smart contract on StaFi chain and the other is cross-chain bridge, StaFi chain is based on substrate and the smart contract’s programming language is Rust while cross-chain bridge is written in Go.