This week, researchers at RootstockLabs and Fairgate Labs released a new whitepaper outlining the design of the UNION Bridge, a major advancement in trust-minimized Bitcoin bridging technology.
Since 2018, the core contributors to Rootstock have led the way in setting the standards for building bridges to Bitcoin with the launch of the POWPeg bridge. To this day, POWPeg remains the most unstoppable, uncensorable, and unbreakable Bitcoin bridge in existence.
Building on that legacy, the UNION Bridge has been designed to be a next-generation Bitcoin bridge capable of securing nation-state scale asset pools, bringing millions of BTC into active use at a scale that underpins massive levels of global economic activity.
Dig into the full whitepaper here.
POWPeg: Best-in-class Bitcoin bridging
In operation since 2018, Rootstock’s POWPeg uses Bitcoin’s proof-of-work and hardware security modules (HSMs) to create a secure, decentralized two-way bridge between Bitcoin and the Rootstock sidechain. PowPeg uses a Defence in Depth approach to security. It relies on multiple technologies such as merged mining to ensure that no single entity controls the bridge, setting a high benchmark for Bitcoin bridging.
UNION Bridge: Pushing the boundaries of what’s possible
The UNION Bridge is a whole new bridge design built for the future. Union employs a multi-party variant of BitVMX, a novel optimistic proving system on Bitcoin.
UNION is a practical and scalable solution for Bitcoin interoperability that maintains strong security and minimizes trust assumptions. It is the first complete design of a secure and efficient bridge that utilizes BitVMX to transfer BTC between networks while preserving Bitcoin’s security guarantees.
Following the publication of today’s UNION whitepaper, a team of core contributors will continue their work to bring this bridge to production.
Why This Matters
UNION sets the stage for an additional secure and efficient way to move BTC into Rootstock, the longest-running and leading Bitcoin sidechain. Once bridged into Rootstock, BTC becomes rBTC where it can be used to build, deploy, and interact with smart contracts and decentralized applications secured by the Bitcoin network.
UNION will supercharge the growth of a decentralized financial system built on Bitcoin, allowing millions of BTC to flow in and out of Rootstock in an efficient, secure, and permissionless manner, all without compromising Bitcoin’s core principles.
Combined with Rootstock’s EVM compatibility, its diverse developer tool support including Alchemy and Gelato, integrations with leading multichain applications, and the decentralized governance, grants, and rewards provided by the RootstockCollective DAO, the UNION bridge will ensure that Rootstock remains the home of DeFi on Bitcoin for decades to come.
Supported by RootstockLabs and Fairgate Labs
The development of UNION is underpinned by the work of RootstockLabs and Fairgate Labs Together, these teams are driving the BitVMX proving system forward, focusing on scalability, security, and user-friendliness. Their joint research has already demonstrated the first-of-its-kind SNARK proof verification on Bitcoin mainnet, and the potential for further advancements, such as decentralized oracles and automated bug bounties running directly on Bitcoin.
As they continue to refine BitVMX’s capabilities, UNION stands as a prime example of how the Bitcoin network can be extended into a robust, decentralized ecosystem without compromising its core principles.
Stay in the know
To stay updated about the research and innovations regarding BitVMX, make sure to join the official BitVMX Builders telegram group and join the Rootstock Discord channel to follow and contribute to the project’s progress.
Recommended reading
The first idea of Bitcoin Virtual Machine (BitVM) was brought by Robin Linus in October 2023, and has improved significantly since.
Explore the concept of BitVM and how it led to the discoveries in BitVMX in this series of research articles: