Newly Formed ZeroSync Association Brings Zero-Knowledge Proofs to Bitcoin

Three German computer scientists have created a Swiss non-profit called the ZeroSync Association to help scale Bitcoin using zero-knowledge proofs (zk-proofs), a cryptographic technique that has exploded in popularity on rival chain Ethereum.

Zero-knowledge proof uses cryptography to prove the validity of information without revealing the information itself. Using a zk-proof to validate the Bitcoin blockchain means nodes can sync almost instantly instead of taking hours (and sometimes days) to download the chain’s current 500GB of data.

ZeroSync has already produced a working prototype that allows users to validate the state (who owns what right now) and transaction history of the Bitcoin blockchain without downloading the entire chain or relying on a third party.

The prototype can verify Bitcoin consensus rules, but not transaction signatures. It’s also a bit clunky and still needs to be optimized for speed and security, so it’s not ready for prime time yet, but the main thing is – it works.

“It’s very much in the prototype stage,” ZeroSync co-founder Robin Linus told CoinDesk. “But the big vision is that you download that one megabyte of evidence and it’s just as good as if you’d downloaded the 500 gigabytes.”

Light clients or simple payment verification (SPV) nodes have always existed on the Bitcoin blockchain. In fact, Satoshi Nakamoto mentioned the concept in his original whitepaper. They are critical for small devices such as cell phones that cannot download the entire blockchain.

“It is possible to verify payments without running a full network node,” Satoshi wrote. “Verification is reliable as long as honest nodes control the network, but is more vulnerable if the network is overpowered by an attacker.”

ZeroSync goes a step further by verifying transactions via cryptographic proof instead of just relying on honest nodes as suggested by Satoshi.

“You don’t have to trust, that’s the whole point,” Linus said. “The evidence proves it to you, it is the great invention.”

A fully functional zk-secure mechanism can be used to enable a wide range of applications beyond flagship node synchronization. ZeroSync has created a developer toolkit to enable applications such as proof-of-reserves on exchanges and transaction history compression on second-layer protocols such as Lightning Labs’ Taro.

Linus and co-founder Lukas George teamed up last July to work on implementing a full chain proof of the Bitcoin blockchain after George’s bachelor’s thesis on implementing a proof of Bitcoin’s headers caught the attention of Geometry Research.

The team then added Tino Steffens to the mix; all three co-founders have a background in computer science.

Linus lived in Santa Teresa, a remote beach town on the Nicoya Peninsula in Costa Rica that has one ATM with a curfew at 10 p.m. It drove Linus crazy and forced him to investigate alternative payment methods. He Stumbled On Bitcoin, Befriended The Well-Respected “Bitcoin Wizard” Ruben Somsen (who coined the term “ZeroSync”) and the rest as they say is history.

“From there, I started learning more and more about cryptography,” Linus said. “I developed some skills over time, and then Ruben recommended me to Geometry Research. They offered me the opportunity to build STARK proof of Bitcoin, and that’s also how I got in touch with Lucas.”