The newly launched ZeroSync Association is bringing zero-knowledge proofs (ZKPs) to Bitcoin (BTC), allowing users to validate the state of the network without the need to download hundreds of gigabytes of blockchain history or trusting a third party.

Based in Zug, Switzerland, the ZeroSync Association is a non-profit entity supported by various community stakeholders, including core contributors Robert Linus, Tino Steffens, Lukas George, and Max Gillett, as well as supporting partners, such as Lightning Labs, among others.

For the first version of its software, ZeroSync is using Cairo, the programming language brought to life by StarkWare, the Israeli-based company developing popular Ethereum layer-2 scaling solutions StarkEx and StarkNet.

“ZeroSync is the first production attempt to radically upgrade the Bitcoin protocol,” StarkWare's ecosystem lead Louis Guthmann told Decrypt. “It would transform the way people think about the system at a fundamental level.”

Commonly referred to as zk-STARKs, StarkWare’s version of ZKPs does not require the potentially vulnerable trusted setup phase, while claiming to be more scalable and efficient than zk-SNARKs—an iteration of ZKP used, for example, by the privacy-focused cryptocurrency Zcash.

StarkWare initially deployed zk-STARKs exclusively on the Ethereum blockchain, and seeing them go live on Bitcoin “is a logical next step,” according to Uri Kolodny, CEO and co-founder at StarkWare Industries.

“This could have a profound effect on how Bitcoin users interact with the network,” Kolodny said in a statement shared with Decrypt.

Faster Bitcoin blockchain sync

To give Bitcoin developers easy access to ZKPs, ZeroSync is developing a software development kit (SDK) that allows them to generate custom validity proofs depending on individual use cases.


A key part of this SDK is ZeroSync’s client which enables fast initial block download (IBD) and the implementation of the first full proof-of-Bitcoin consensus.

Syncing the Bitcoin blockchain can be a painful process as, depending on your internet connection speed, downloading the history of transactions can take days or even weeks, with new blocks added every ten minutes on average.

According to ZeroSync, its client can be used not only to sync a full node much faster but also without needing to make any code changes to the Bitcoin Core software.

The technology can also be applied to compress the transaction history of validation protocols such as Taro, a protocol for issuing stablecoins on Bitcoin’s Lightning Network, or, for example, to enable Bitcoin exchanges and custodial services to provide proof-of-reserves.

“After years of frustration about slow syncing, users will be able to sync with the network much faster, and with less computation. It’s a technological leap akin to the transition from slow dial-up internet to high-speed broadband,” said STARKs co-inventor and StarkWare president Eli Ben-Sasson.

While StarkWare, which funds the initiative along with Geometry Research, plans to keep its focus on Ethereum, for Ben-Sasson personally this development “closes a circle.”

The StarkWare president recalled a Bitcoin conference held in 2013, where he had “the ‘eureka’ moment” recognizing the cryptography he helped to invent could change blockchain.

“But it was clear that the journey needed to start on Ethereum. Now, exactly ten years later, STARKs have proved themselves on Ethereum and are heading to Bitcoin reaching new horizons,” said Ben-Sasson.


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