As Bitcoin interoperability advances, a persistent challenge remains: building secure, scalable bridges without locking up vast amounts of idle capital.

Most existing optimistic bridges require large, permanent security bonds, creating high financial overhead and excluding smaller participants from operating.

FLEX (Fraud proofs with Lightweight Escrows for eXits) introduces a breakthrough approach to this problem.

Built using garbled circuits and compatible with the BitVM and BitVMX ecosystems, FLEX enables on-demand security bonds that are only activated when a dispute arises. This reduces costs without compromising security.

Instead of operators locking funds indefinitely, FLEX’s design allows them to post bonds dynamically, ensuring they are only at risk when their behavior is actually contested.

The result is a bridge architecture that is more capital-efficient, decentralized, and resilient to denial-of-service attacks, while maintaining compatibility with Bitcoin’s existing consensus rules: no soft-forks or opcode changes required.

Beyond bridging, the FLEX model offers a general framework for dispute resolution in payment channels, rollups, and smart contract execution over Bitcoin.

Read the full paper 🔗here