Bitcoin startup Chainway has taken a significant stride in the space with its introduction of the first Ethereum Virtual Machine (EVM) transaction on bitcoin. This is part of Chainway’s continued efforts to implement ZK rollups on bitcoin, a move that may offer enhanced scalability and privacy features to bitcoin.

Chainway’s recent demonstration serves as a proof of concept, illustrating how their future ZK rollup is intended to function when integrated with bitcoin. This integration seeks to combine the flexibility and programmability commonly associated with EVM and the robust security infrastructure inherent to bitcoin.

Diving deeper into the mechanics, rollups work by grouping transactions occurring off-chain, batching them, and then publishing this consolidated batch onto the bitcoin blockchain. This process significantly optimizes computational efficiency while still benefiting from the foundational security of the bitcoin network.

The inclusion of the zero-knowledge or ‘ZK’ variant in rollups introduces a layer of cryptographic privacy. Zero-knowledge proofs enable one to confirm the veracity of a transaction without having to disclose its specific details. With ZK proofs embedded, the system not only maintains transactional privacy but also ensures mathematical certainty, rooted directly into bitcoin infrastructure.

The foundation of Chainway’s approach is a synthesis of zero-knowledge proofs with the Ordinals protocol. Chainway’s rollup is designed to publish L2 state proofs and represent a consolidated set of transactions. Through a meticulous process, Chainway’s ZK circuit will scan each bitcoin block, extract prior state proofs for verification, and incorporate user-driven transaction envelopes into the current batch.

A noteworthy aspect of Chainway’s initiative is its execution layer, powered by the EVM –– a feature familiar to those acquainted with the Ethereum ecosystem. The team at Chainway has successfully embedded the EVM into a ZK-STARK-based virtual machine, resulting in the creation of the zkEVM. This new architecture is designed to produce zero-knowledge proofs for the rollup’s state transitions, ensuring both transactional transparency and privacy. Furthermore, Chainway’s rollup is developed to be fully compatible with EVM, suggesting that tools and utilities familiar in the Ethereum ecosystem such as Metamask could be integrated seamlessly.

Comparing Chainway’s rollup with existing EVM sidechains provides clear distinctions. Notably, Chainway’s rollup operates without the dependency on a separate network of nodes. It’s built directly on bitcoin’s infrastructure. In contrast, current sidechains don’t leave an actual imprint on bitcoin, and as such, their transactions cannot be validated by simply examining the bitcoin blockchain.

Chainway’s efforts to integrate Ethereum’s EVM with bitcoin’s infrastructure represent a thoughtful and considered approach to enhancing bitcoin’s potential functionalities. By aiming to merge the flexibility of Ethereum with the security of bitcoin, Chainway’s potential implementation of ZK rollups on bitcoin could signal a new phase in the space.

While a soft fork would be necessary to unlock the full capabilities of a ZK rollup on bitcoin –– i.e. a real trustless peg mechanism between the rollup and on-chain bitcoin –– this approach seems to strike a good balance between the ideal and what is possible without any changes to bitcoin. Indeed, this advancement could already be quite useful for trustless Ordinals-based tokens such as BRC-20s.

​ The first Ethereum Virtual Machine transaction on bitcoin has been achieved, the latest milestone towards the launch of a BTC-based ZK rollup.