Blockchain developers have released a whitepaper for BitVM2, presenting new updates to Bitcoin sidechain technology and introducing a new bridge design.

The developers of Bitcoin (BTC) scaling solution BitVM have unveiled its second version, bringing permissionless challenging features and reducing the complexity and number of on-chain transactions required to resolve disputes.

In an Aug. 15 announcement on X, Alexei Zamyatin, a co-founder of Build on Bitcoin, a hybrid layer-2 powered by Bitcoin and Ethereum, said the updated version aims to enhance the security of BitVM by allowing anyone to challenge transactions within the system, minimizing the on-chain footprint to just three transactions for dispute resolution.

BitVM2’s whitepaper reads that the construction mechanism “requires no consensus changes” to the Bitcoin network, enabling the design of an “entirely new class of applications” on the blockchain.

“To guarantee liveness, we only require one active rational operator (while the others can be malicious). Any user can act as challenger, facilitating permissionless verification of the protocol.”

BitVM2 whitepaper

BitVM’s Bridge design — which is touted as “the most secure BTC bridge to date” — employs a 1-of-n security model, allowing anyone to challenge and prevent unauthorized transactions, contrasting with the traditional t-of-n multisig approach that relies on the assumption of an honest majority.

Solving scalability challenges

Authored by Robin Linus, Zamyatin, Lukas Aumayr, Andrea Pelosi, Zeta Avirikioti, and Matteo Maffei, the whitepaper notes that nearly all existing Bitcoin bridges rely on multi- or threshold signature schemes, where a group of t-of-n signers is entrusted with safeguarding Bitcoin.

Although some bridges employ economic security through collateralization, the authors say these designs “face scalability challenges due to high capital requirements and have thus achieved limited adoption in practice.”

First unveiled in October 2023, BitVM aims to redefine Bitcoin by enabling smart contract-like functionalities without transforming it into Ethereum. The project has spurred initiatives like Bitlayer, aimed at advancing layer-2 solutions on the Bitcoin network.