Bitcoin Bridging: Limitations of Past Approaches and the Potential for the Broader DeFi Space

Bitcoin bridging has long been a technical and philosophical challenge, while other blockchain networks have embraced interoperability with relative ease.

Despite the growing demand for decentralized bridges to facilitate crosschain transactions, Bitcoin has faced unique challenges due to its limited scripting language and strict consensus rules. This has hindered efforts to integrate Bitcoin into the broader decentralized finance (DeFi) ecosystem.

However, recent advances in Bitcoin Virtual Machine (BitVM) protocols aim to address these limitations and open up new possibilities for Bitcoin bridging. In an exclusive interview with Cointelegraph, Sergio Lerner, science specialist at RootstockLabs, discussed these developments and their implications for the DeFi space.

Highlighting the limitations of past approaches to Bitcoin bridging, Lerner explained that Bitcoin's scripting language was not designed to support the complex computations needed for validating crosschain transactions.

“Bitcoin did not have a language expressive enough to support [decentralized bridges],” he said.

This constraint has limited efforts to build fully decentralized and trust-minimized bridges.

While BitVM protocols can introduce disputable computing to verify complex computations on Bitcoin, early versions of these protocols were inefficient, and Lerner noted that some trade-offs must be considered.

“A limitation of every BitVM protocol is that it needs covenants for Bitcoin, and without covenants, they must emulate them with a committee that co-signs a set of transactions,” he said.

This approach introduces trusted parties into the system, as at least one committee member must act honestly to maintain security.

“This limitation does not exist in two-party protocols based on BitVMX, such as payment channels,” Lerner said. “It only arises when the protocol must provide an open service to other unknown parties.”

Lerner also mentioned BitVMX as an alternative method for Bitcoin bridging, which enables participation in broader blockchain applications.

“BitVMX is currently the cheapest and most resource-efficient disputable computing protocol for Bitcoin,” he said, adding that it could be used to build validating bridges for the network.

However, Lerner emphasized the importance of careful testing and deployment to mitigate risks, stating that any team rushing to deploy a BitVM-based system without proper testing “will be playing with users' money.”