BATTLE for Bitcoin: Capital-Efficient Optimistic Bridges with Large Committees
Sergio Demian Lerner, Ariel Futoransky
TL;DR
BATTLE for Bitcoin addresses the challenge of building a DoS-resilient dispute layer for optimistic Bitcoin bridges by adapting a two-phase tournament to Bitcoin’s UTXO model. It leverages FLEX garbled-circuit disputes with on-demand L1 security bonds and a Tournament Chain to serialize tournament openings, enabling $O(\, ext{log}\,C)$ rounds while keeping the honest asserter’s minimum capital constant. Phase 1 eliminates competing asserters via enabler chains and a fixed bracket, then Phase 2 escalates disputes against registered challengers with recycled rewards funding subsequent rounds, achieving scalable, capital-efficient dispute resolution. The design also introduces contestable FLEX components and two practical implementations (dual-proof input and score-carry) to defend against non-canonical assertions, and discusses extensions to disable losing parties and reduce input-publication costs. Overall, BATTLE provides a Bitcoin-native path to DoS-resilient, constant-capital dispute resolution suitable for large, permissionless operator sets.”
Abstract
We present BATTLE for Bitcoin, a DoS-resilient dispute layer that secures optimistic bridges between Bitcoin and rollups or sidechains. Our design adapts the BATTLE tournament protocol to Bitcoin's UTXO model using BitVM-style FLEX components and garbled circuits with on-demand L1 security bonds. Disputes are resolved in logarithmic rounds while recycling rewards, keeping the honest asserter's minimum initial capital constant even under many permissionless challengers. The construction is fully contestable (challengers can supply higher-work counter-proofs) and relies only on standard timelocks and pre-signed transaction DAGs, without new opcodes. For $N$ operators, the protocol requires $O(N^2)$ pre-signed transactions, signatures, and message exchanges, yet remains practical at $N\!\gtrsim\!10^3$, enabling high decentralization.