Swim’s Propeller Design

  • Usability: Smart contracts often depend on user transactions to facilitate cross-chain activity. Manually clicking through several approvals and transactions during the bridging process is common.
  • Decentralization: Cross-chain communication involves several intermediary steps, each with a variety of failure scenarios, making designing trustless and safe technology hard
  • Liquidity: Most bridging solutions rely on multiple liquidity pools and output a wrapped asset on the target chain. This leads to liquidity fragmentation.

Swim’s Current Ecosystem

Swim’s Hexapool of stable assets allows users to swap native tokens across Solana, Ethereum, and the Binance Smart Chain.

Swim’s Propeller Design

The Propeller’s design will implement a trustless mechanism that allows for asset bridging with a single click. It’s a high-impact milestone for our protocol.

Setting the Stage for Propeller

In cross-chain asset swaps, three terms are important:

  • Source chain: The user is moving tokens off this chain. Their initial assets become locked on it.
  • Engine: It monitors the network and posts Solana VAA’s (a message emitted by the Swim contract combined with Guardian signatures). The Propeller server is off-chain.
  • Target chain: The user receives funds on this chain. It obtains information from the server during a swap.

Propeller Design Details

The Propeller design allows our protocol to move away from user-prompted transactions. It enables the protocol itself to send smart contract calls. They’re encoded from the source chain, invoked by the engine, and eventually reach the target chain. Swim’s Propeller is the trustless mechanism that cranks through these calls.

Current Swap Process (EVM to Solana)


Propeller Design Swap Process (EVM to Solana)


Propeller’s Immediate Impact

The Propeller design significantly improves usability without sacrificing the decentralization of our cross-chain swapping protocol. We substantiate that claim with these five points:

  • Users are no longer required to manually confirm transactions. Elegantly swap assets with a single confirmation.
  • Users do not need tokens to pay gas on the target chain.
  • Swaps do not require a Solana wallet address for non-Solana transfers (Ethereum to BNB Chain, for example).
  • The process can be performed on mobile devices.
  • Less human interaction means less opportunity for human error.

Thoughts on Propeller’s Future

At Swim, we believe blockchain’s future should be interconnected and we’re building it. While the Propeller design will initially be implemented for cross-chain swaps, it has potential to become a primitive for cross-chain smart contract invocation. A few possibilities for the future:

  • By creating more general Propeller Smart Contracts, the Propeller could seamlessly handle complex interactions such as converting the GST SPL you earned on StepN to ETH on Ethereum to bid on an NFT you’ve been eyeballing
  • The Propeller engine has been designed to eventually become fully decentralized by allowing anyone to run an a Propeller service and be paid in fees, similar to running a validator
  • Offering a multi-chain bridge built into the backend of wallet extensions and dashboards. This would allow users to seamlessly swap cross-chain assets directly in their wallets (MetaMask, Phantom, etc.)

Relayers in the space

Credit to Wormhole’s Relayer which Swim’s Propeller is an extension of: https://github.com/certusone/wormhole/tree/dev.v2/relayer/spy_relayer



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Swim Protocol

Swim Protocol


Please visit our new blog at: http://blog.swim.io/ Swim provides a simple way to transfer tokens across chains via multi-token liquidity pools and Solana's Worm