Zero-Knowledge Proof is Coming to Bitcoin, Overtaking Network State Validation

Bitcoin (BTC) users will soon be able to use zero-knowledge proofs (ZK proofs) to speed up the process of verifying individual blocks and eventually the entire blockchain.

The ZeroSync Association, a Swiss-based non-profit organization, is developing tools that allow users to validate the state of the Bitcoin network without having to download the blockchain or rely on a third party for verification.

ZeroSync was formed to develop and maintain open source software that enables concise ZK proofs on the Bitcoin blockchain. The group uses StarkWare’s proprietary Zero-Knowledge Scalable Transparent Argument of Knowledge (zk-STARK) proof of validity to generate ZK proof for the Bitcoin network.

The tool promises to overhaul the process of verifying the Bitcoin blockchain, which still requires node operators to download a large amount of data to synchronize the correct state of the Bitcoin network.

ZeroSync uses ZK proofs to ultimately generate valid proofs and verify the latest state of the blockchain almost instantly.

ZK proof has been a revelation for the Ethereum ecosystem, with various proof methods powering several layer-2 scaling platforms, including Polygon, Arbitrum, Optimism, and StarkNet.

Related: Polygon’s ‘holy grail’ Ethereum-scaling zkEVM beta hits mainnet

An announcement from the ZeroSync Association highlights the promise of ZK proof for blockchain scalability and privacy by providing “nearly fixed-size” proofs that verify large computations.

The project’s work pioneers the application of ZK proof for the Bitcoin network, with the organization describing Bitcoin’s relative simplicity and the Unspent Transaction Output (UTXO) model as a unique value proposition for using recursive proof.

ZeroSync notes that the ZK-Proof tools do not require consensus changes or additional trust assumptions for the Bitcoin network and its users. The organization is building a software development kit that will allow developers to generate custom proof of validity for specific use cases without requiring deep domain expertise.

ZeroSync is in the process of building a client for fast initial block download as well as implementing the first complete proof of Bitcoin consensus. The client will allow users to sync a full node without making code changes to the Bitcoin core.

ZeroSync uses the Cairo programming language, developed by StarkWare, to create STARK-proven programs for calculations.

ZeroSync’s tool is currently in a prototype state, but has the ability to prove the validity of individual putatively valid blocks, verifying all Bitcoin rules except scripts. The team also has a working in-browser demo proof of STARK proof of Bitcoin blocks.

The ZeroSync Association was originally funded by Geometry and StarkWare, but is establishing a non-profit entity to enable ongoing development and maintenance by stakeholders in the Bitcoin community.

A statement from StarkWare president and co-founder Eli Ben-Sasson, who co-invented zk-STARKS, summarized the scope of ZK proofs coming to the Bitcoin ecosystem:

“After years of frustration with slow synchronization, users will be able to synchronize with the network much faster and with less computation. It’s a technological leap similar to the transition from slow dial-up Internet to high-speed broadband.”

Lightning Labs, the team behind the Bitcoin layer-2 Lightning Network payment system, is a contributing partner to ZeroSync’s project.

The firm intends to use ZeroSync to power compressed transaction history proofs for its Taproot Asset Representation Overlay (Taro) protocol, which aims to power the issuance of digital assets on the Bitcoin blockchain.