While the Blockchain Transmission Protocol (BTP) might be the ICON network’s most cutting edge interoperability solution, it’s also very much a “work in progress.”

To jump start interoperability, ICON released ICON Bridge, an “early iteration” of BTP. ICON Bridge uses much of the same technology as BTP, albeit in a permissioned, centralized way.

With other blockchain bridges subject to recent high profile attacks, ICON is taking care to ensure the solution’s security.

The ICON Bridge will have the same level of safety as other centralized bridges once the audit finishes in Q4 2022,” says ICON senior manager Cyrus Vorwald.

We take additional precautions when compared to other bridges by limiting individual transaction size and banning anomalous wallet addresses in the event of a breach. We also plan to limit TVL and scale up over time.”

What is ICON Bridge?

As we’ve explained earlier, BTP’s most innovative feature is its reliance on so-called “light clients,” represented by the BTP Message Verifier Contract. Light clients are essentially mini copies of the source blockchains. These mini-blockchains enable smart contracts to verify cross-chain transactions in a completely trustless manner, which is to say, without the need for human intervention.

However, given how blockchains are constantly changing as new blocks are produced, light clients need constant updating, incurring prohibitively high gas fees.

While ICON and its chief technology partner ICONLOOP work to resolve the fee conundrum, ICON released the interim bridging solution ICON Bridge.

ICON Bridge works in a very similar way as BTP, with the key difference being that verification occurs off-chain, with the ICON Foundation serving as the sole relay operator passing messages and verifying transactions between chains.

Tokens get locked up on the source chain and minted as a wrapped version on the destination chain,” says Cyrus. “The centralized relay picks up cross chain messages, verifies them, and executes them.”

Like BTP, ICON Bridge enables cross-chain transfers, it’s compatible with all blockchains, is eligible for ICON’s 200 million ICX incentive program, and boasts extensible messaging capability.

All it really lacks in a trustless structure.

The release of ICON Bridge mirrors the development of the ICON network itself, with the ICON Foundation serving as the network’s sole validator prior to the transition to full decentralization in 2019.

Interoperability in action

People are free to use ICON Bridge, with the caveat that the audit is still ongoing — use it at your own risk.

The solution currently supports cross-chain transfers between ICON and Binance Smart Chain (BNB Smart Chain).

Pre-audit status aside, ICON Bridge has already notched a couple of impressive use cases.

The collaborative DeFi game Wonder Game put ICON Bridge to use during its historic presale, allowing users to mint NFTs on the Harmony blockchain with ICX.

Cyrus notes a number of other current and near-future use cases:

  • ICON’s decentralized exchange Balanced uses ICON Bridge for overcollateralization of BTCB (i.e., bitcoin from BNB Smart Chain). Work is currently ongoing on creating a custom interface for ICON Bridge for Balanced’s Trade page.
  • Craft Network, ICON’s premier NFT marketplace, is expanding to enable cross-chain NFTs using ICON Bridge. Potential use cases include cross-chain NFT purchases and creating a cross-chain launchpad.
  • The ICON Bridge team is talking with P-Rep team Staky to possibly adopt ICON Bridge for Everest Bridge, a liquidity onboarding solution for SNOW, ICON’s parachain for Polkadot’s canary network Kusama.

Cyrus notes, however, that ICON Bridge will eventually morph into BTP as the latter comes into being, reflecting the former’s interim status.

The ICON Bridge will transition to BTP over time as its specifications get released and development resources free up,” he says. “We are beginning to add the xcall  (Arbitrary Call Service) specification to the BSC and ICON service handlers next month.”

Open source wisdom at work

If you’re a developer who wants to implement ICON Bridge into your project, Cyrus recommends you go to ICON Bridge’s Github, where there is extensive documentation to help you get started.

The project is in active development and assists any project’s questions in getting started directly on the Github issue and discussion boards,” he says.

ICON Bridge is an open source project, and as such, it benefits from public support.

The Icon Bridge repository is open source and we value the open source community,” says Cyrus. “Please post any comments, questions, or concerns directly on Github and be sure to star the repository on Github if you want to support the project.”