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ucs03-zkgm-1

Overview

ucs03-zkgm-1 is the most advanced and recommended protocol to use for

  • message passing
  • transfers (assets and NFTs)
  • intents
  • storage proofs

It’s the most gas-efficient version and suitable for almost all use cases.

Protocol

There are two main modes for a packet to be transferred using ucs03-zkgm-1. The main mode, which always succeeds for any chain, leverages state lenses to create a recursive connection and a communication channel between two chains.

The packet submission is not routed through any PFM middleware, which avoids re-execution on Union, unlike ucs01-relay-1. The core protocol is significantly more gas efficient over multi-hop-based protocols.

Open Filling

A groundbreaking protocol improvement on IBC and trust-minimized bridging in general, is that ucs03-zkgm-1 allows arbitrary filling of orders by any party.

For packet submissions and transfers, the protocol allows a different filler from the Union IBC contracts. In the case of an alternative filler, the assets are not minted but transferred from the filler’s account. This allows a transfer to be filled before chains have been finalized or client updates processed. Instead, fillers can rely on preconfirmations to reduce the risk of reorgs.

Theoretically, a filler can submit the transfer to the destination side before the transaction is included on the source, given that they protect themselves against double-spend attacks.

The Acknowledgement, which may contain arbitrary payloads, is used to encode information on the filler and repay the filler for the service by unlocking assets from the vault.

Open filling is opt-in for any protocol, allowing for the same optimizations that ucs03-zkgm-1 leverages to increase transfer speeds.

Batching

To minimize the cost of packet verification (which is dominated by membership proofs), packets may be batched. This means that at scale, the gas cost of transfers tends to the erc20 gas cost, which is the theoretical optimum.