At the beginning of this year, x.com/weikengchen”>Weikeng Chen and his partners in the venture firm L2 Iterative They decided to turn their attention to the burgeoning bitcoin ecosystem. Chen, a Chinese native, had noticed the growing interest in bitcoin development from several major players in the mining space who began backing different projects in the Ordinal and Layer 2 space.
“I never realized bitcoin had a development community,” he says, half joking.
Fast forward to last week, an open source initiative led by himself, with sponsorship from an infrastructure company Starkwarehas achieved the bitcoin-Wildlife-Sanctuary”>first implementation from a zero-knowledge verifier using a bitcoin script.
In an industry where significant breakthroughs are few and far between, those involved in the project are excited about the significance of this milestone. Zero-knowledge proofs, they argue, are the key to unlocking bitcoin’s programmability and expanding its use globally.
Behind this achievement lies the extraordinary journey of an outsider who got into bitcoin development just six months ago and has now coded arguably its most advanced piece of software. I interviewed Weikeng Chen to dig deeper into his motivations, his collaboration with Starkware around OP_CAT and STARKs, and his perspectives on this new era of bitcoin development.
Starting from scratch
Chen, a PhD graduate from the University of California at Berkeley with a specialization in cryptography, explained that he began looking for an opportunity to contribute his technical skills to the industry to better position his company to potential investors and businesses. Despite his extensive engineering background, he quickly realized that resources were scarce and the learning curve was steep. “A lot of the material out there is outdated and doesn’t reflect the current state of development.” His affinity for zero-knowledge technology eventually led him to bitcoin“>investigation focus on bitcoin's ability to perform the computations necessary to verify zero-knowledge proofs.
Like one rabbit hole leading to another, Robin Linus' His work on the new computing paradigm BitVM caught his attention. Interested in the potential of using fraud proofs to implement bitcoin-compatible zero-knowledge systems, he began poking around in the white paper and noticed some issues with some of the concepts involved in the system. “I sent a message to Robin asking him some questions about BitVM. My understanding of BitVM from that white paper was really flawed. I remember Robin’s first reaction was to ask me who told me this,” he recalls with a laugh. This interaction sparked a brief but productive collaboration between Chen, Linus, and other researchers as they iterated on the original idea and looked for ways to optimize it.
“It became obvious to me that this method could be used to verify zero-knowledge proofs, so my work quickly turned to implementing a SNARK verifier.”
A verifier is a cryptographic tool that enables the verification of zero-knowledge proofs on the bitcoin network.
The OP_CAT opportunity
Around the same time, a team at zero-knowledge industry giant Starkware was paying close attention to the emerging activity coming out of the bitcoin community. For some, it was long overdue. Starkware founder Eli Ben-Sasson was arguably the first to first person to discuss Zero-knowledge technology in the context of cryptocurrencies at an early bitcoin conference. Nearly a decade later, Starkware's research and ZK-STARK technology serve as the foundation for a growing number of applications in the space.
“In 2013, when I suggested using proofs of validity to scale bitcoin, I hoped that Satoshi would still be around and would make it happen faster. Thanks to cryptography visionaries like Weikeng Chen and bitcoin OP_CAT researchers like Andrew Poelstra and Ethan Heilman, my 11-year dream now seems within reach,” Ben-Sasson said.
Last month, the company announced that it was beginning to implement numerous initiatives focused on bridging the technological gap between bitcoin and zero-knowledge proofs. A $1,000,000 grant was offered for research and exploration of the potential of the OP_CAT soft fork proposal.
The announcement was marked by a remarkable amount of enthusiasm, leaving some wondering what was driving this optimism. Until recently, the prospects of zero-knowledge technology in bitcoin had mostly been an afterthought – another OP code that might never see the light of day. Indeed, the difficulty of achieving consensus on minor changes to the bitcoin codebase made it seem unlikely that anything more complex would ever happen.
According to conversations with Starkware contributors, it was around May when they heard about Weikeng’s progress on BitVM and the mood changed dramatically. Apparently, the developer had already set his sights on the company’s Circle STARKs technology. In an article published a couple of months ago, Chen had already identified the latter as a “bitcoin-compatible test system.”
After some back-and-forth, both sides agreed to come together and launch a joint effort dedicated to an open-source implementation of a STARK verifier using the OP_CAT primitive. “I knew it could be done. We just needed to put all the pieces together,” Chen suggests.bitcoin-Wildlife-Sanctuary”>bitcoin Wildlife Sanctuary” born.
Two months later, the project seems to have reached its goal thanks to the collaboration of other developers such as Pingzhou Yuan, another of BitVM's first contributors. Late last Friday morning, Chen joined the project's Telegram group to break the news to the other participants: “I think I've finished the job!”
Following the success of local testing, the developer released a series of transactions to the bitcoin Signet testnet that would run the entire script. To optimize on-chain usage, the STARK testnet, based on Starkware's open source Creature The implementation is divided into concurrent transactions chained together by an OP_CAT-based pact.
At 6:29 am on July 12, 2024, the final transaction was confirmed on the Signet network, signaling what proponents believe could be the beginning of a new era of development in bitcoin.
“It was a massive effort and took a significant amount of time,” Chen said. “We started with nothing. There is no information about ZK proofs in bitcoin. There is no information about the mathematical operations to follow. We had to build the entire stack, which ultimately led to the implementation of the STARK verifier.”
Inspiring a new path of development
While the results are worth celebrating, Chen insists the work is not done. When asked if he was optimistic about his work to create the foundation for new scaling protocols like bitcoin rollups, the developer was quick to temper expectations.
“The idea works in broad terms, but the proof of concept is not ready for production. Validity tests also take up a lot of block space, which could prove costly in the future.”
Starkware’s contributors acknowledge the challenges ahead, but are confident that the project’s success represents “a monumental leap forward” toward bitcoin scaling solutions that can leverage its ZK rollup technology.
One thing is certain: the collaboration is likely to further strengthen the case for a potential OP_CAT soft fork. To put together the verifier implementation, Chen says he had to develop a reliable framework for CAT-using conventions that can serve to highlight the versatility of the proposed script improvement. He believes other developers in the ecosystem can play around with his code and come to the same conclusion he did regarding its benefits.
“I don’t think there are many risks once we have developed best practices. There are not many places where this can go wrong. We now have a clear demonstration that OP_CAT can be adapted to various convention projects in a safe way.”
When asked about his intention to contribute to a future activation process, the developer readily admitted that he is not yet sufficiently familiar with the entire dynamics surrounding bitcoin open source development. He intends to share his progress with the members of the development mailing list next and hopes that others will be able to contribute to the review and provide feedback on his work.
Reflecting on his experience so far, Chen immediately points to the importance of creating a fertile environment for new developers entering the ecosystem. He believes that many talented developers are missing out on the opportunity to develop bitcoin due to a lack of a cohesive vision.
“There is no clear sense of direction at the moment, leaving contributors perplexed about their ability to influence the future. Hopefully, the emergence of new tools and primitives can improve this situation so that Bitcoiners can dream again.”
