StarkWare plans to bring ZK scaling to Bitcoin alongside Ethereum

Blockchain developer StarkWare has announced plans to build a Bitcoin scaling solution in a significant expansion pivot.

StarkWare, which was valued at $8 billion in its last investment round, is the core contributor to Ethereum Layer 2 Starknet. With the new Bitcoin OP_CAT proposal currently being debated in the community, the firm says it's the right time to bring its zero-knowledge scaling technology to Bitcoin.

“Starknet will become the first network to settle simultaneously on Bitcoin and Ethereum, and scale Bitcoin to many thousands of transactions per second. This will happen within six months after the potential Bitcoin upgrade, OP_CAT,” StarkWare CEO and co-founder Eli Ben-Sasson said in a statement shared with The Block.

No extra chain is being created — the plan uses the same Starknet network with the same governance and tokenomics, supporting Bitcoin scaling without requiring a fork, the team clarified. Every dApp could choose where it wants to settle — either or both, Ben-Sasson told The Block.

“StarkWare is often mistaken for being an Ethereum maxi, though actually we are scaling maxis,” Ben-Sasson added. “We’re mass-use maxis. We’re STARK maxis, which means we believe our technology is best suited to scale all blockchains safely and efficiently. At StarkWare, we now have the expertise, experience and team to simultaneously scale both Ethereum and Bitcoin.”

StarkWare also announced the introduction of a $1 million application-based fund for Bitcoin researchers interested in contributing to its plans. Applications will open “within weeks,” Ben-Sasson said, with funds “earmarked for new discoveries which demonstrate risks associated with OP_CAT, or open source and useful proofs of concept.”

Bitcoin scaling discussed internally 'for a long time'

Bitcoin scaling is something that has been discussed internally at StarkWare for a long time, according to the team, with Ben-Sasson giving a talk on STARK scaling at a Bitcoin conference as early as 2013.

StarkWare said Bitcoin wasn’t previously ready for STARKs, but Ethereum was — making it the “obvious first chain to scale.” However, research following Bitcoin’s Taproot upgrade in November 2021 means Bitcoin is now “primed” for scaling, having lifted many of its “restrictive features,” enabling further experimentation and innovation, StarkWare added.

“Bitcoin today is mighty, but still a fraction of what it can be,” Ben-Sasson said in the statement. “I want to see the full works. The STARK cryptography we are proposing can deliver everything Satoshi envisioned, including the cheap everyday micro-payments discussed in the Bitcoin White Paper.”

“I left academia because I’m convinced that crypto can clean up the digital world and finance. It can deliver integrity to money and rebalance power in our society, taking it away from big tech and restoring it to sovereign individuals. It’s a tool to empower humans and grassroots communities. In short, it's a source of good,” Ben-Sasson added. “To me, no such vision is complete without scaling the chain that started this great project. Scale Bitcoin and we unleash blockchain’s power to transform the world.”

Why OP_CAT?

Covenant proposals like OP_CAT are advanced scripting features that allow for specific conditions on how bitcoins can be spent in future transactions. They could enable use cases, including the creation of secure "vaults" that allow reversible transactions, automated recurring payments, time-locked transfers for scenarios like inheritance, and complex financial instruments such as escrows and bonds.

The concept of covenants in Bitcoin has been discussed for several years, dating back to at least 2013, with Check Template Verify (CTV), OP_CHECKSIGFROMSTACK (CSFS) and LNHANCE being other examples.

OP_CAT was originally included as one of the first opcodes in Bitcoin. However, pseudonymous creator Satoshi Nakamoto disabled it alongside several other opcodes in 2010 due to concerns surrounding the potential for creating scripts that could lead to vulnerabilities.

An opcode refers to a command used in the scripting language that makes up part of the Bitcoin protocol. Bitcoin scripts are made up of sequences of opcodes, each of which performs a specific operation.

The proposal , authored by Ethan Heilman and Armin Sabouri, seeks to reintroduce OP_CAT to Bitcoin via a backward-compatible soft fork, without altering other aspects of the script's operational limits.

According to the proposal, the OP_CAT opcode would simplify and expand Bitcoin’s functionalities, including making decentralized protocols more practical and supporting advanced multi-sig setups. Essentially, OP_CAT would significantly increase the power and flexibility of Bitcoin scripting, making it easier to develop more sophisticated applications directly on the Bitcoin blockchain, the authors argue.

The likelihood of any such OP_CAT soft fork is contingent on a combination of technical, security and community consensus considerations. Without broad agreement and a clear demonstration of its safety and utility, OP_CAT's implementation remains uncertain.

However, Ben-Sasson is more optimistic. “It seems clear we are approaching rough consensus with clear consensus among some subsets of the community. When I reflect on the past, it's remarkable how quickly the conversation around scaling has shifted. Not long ago, at Ethereum events, scaling was merely a side topic, and now it's taking center stage,” he told The Block.

StarkWare said OP_CAT would provide a framework on Bitcoin that is just enough to enable STARK scaling. STARKs use zero-knowledge proofs to allow for the verification of large computations without revealing the data involved or requiring extensive computational resources. STARKs provide scalability by enabling the compression of complex transactions into succinct proofs, which can be quickly verified.

The firm added that it was committed to “publicly champion” OP_CAT to demonstrate “the potential it can unlock and the benefits to Bitcoin and to the blockchain community in general.” It said it is working on the solution now so that if OP_CAT is approved, it has “ready-to-roll” practical plans for deploying STARK scaling on Bitcoin.

“We’re supporting OP_CAT because we believe Bitcoin should play a more central role in society and we believe that the OP_CAT Bitcoin soft fork is the safest path for Bitcoin to scale, notably enabling STARK and rollups,” Ben-Sasson said in the statement, while stressing that he is not advocating changing the Bitcoin block size or any other sweeping changes. 

OP_CAT concerns

Not everyone in the Bitcoin community is behind OP_CAT, with some advocating for other covenant proposals, while others are concerned at potential unintended consequences deriving from such an implementation.

Ben-Sasson said he had questions about the proposal too, but that was the point of the $1 million fund and its internal research — to address any challenges and “ensure everything is done safely.”

When asked if StarkWare’s plans were solely reliant on OP_CAT or if there were any other proposals under consideration, Ben-Sasson said, "OP_CAT is the most efficient way of getting there, but not the only way. We're currently exploring alternative solutions to achieve STARK scale without relying on OP_CAT. While I can't delve into details at this moment, these alternatives hold promise and could potentially serve as a viable workaround."

Regarding current Bitcoin scaling solutions, Ben-Sasson said. “There are some great initiatives, several of which we support. But the level of self custody and the ability to scale are not the same. But we want to see a trajectory to the holy grail of blockchain — mass scale so that both of the biggest chains are usable by all, constantly. That’s what differentiates the new proposal.”

StarkWare claims it is already a major supporter of the Bitcoin network, backing Bitcoin projects such as ZeroSync, which is working on the integration of ZK proofs with Bitcoin to enhance scalability. StarkWare said it also recently commissioned the "Validity Rollups on Bitcoin" report by Bitcoin researcher John Light, reassessing the potential for integrating validity rollups with Bitcoin.

“Starknet will deliver far more than the ‘bandwidth’ needed for the original vision of the Bitcoin Whitepaper,” Ben-Sasson said. “Applications for anything and everything will be deployable over Bitcoin, something that is impossible today.”