ZK-proofs are bringing good contracts to Bitcoin — BitcoinOS and Starknet

BitcoinOS and Starknet aren’t ready round for the controversial OP_CAT onerous fork so as to add new performance to Bitcoin, with each tasks devising revolutionary methods to scale Bitcoin utilizing zero-knowledge (ZK) proofs proper now.

The tasks have each demonstrated it’s attainable to confirm ZK-proofs on Bitcoin’s present mainnet — even when Bitcoin’s ultra-simple scripting language makes it troublesome and costly. This might create real Bitcoin L2s that inherit a lot of its safety, and unlock the intriguing risk of making programmable tokens on Bitcoin itself.

Greatest generally known as an Ethereum L2, Starknet needs to make use of the tech to scale Bitcoin to hundreds of transactions per second, up from simply 7 TPS right this moment. “The ecosystem in Starknet could be very, very passionate about additionally increasing to Bitcoin,” co-founder Eli Ben-Sasson tells Journal. 

BitcoinOS, in the meantime, claims it can quickly unveil know-how that unlocks “good contract performance instantly” on Bitcoin’s mainnet itself, moderately than requiring BTC to be despatched to a Bitcoin L2. This might allow nearly $2 trillion of Bitcoin for use natively in DeFi. 

“That’s an entire lot of cash simply sitting there and doing nothing,” says CTO Gadi Man. “We wish to put this cash to work.”

In November, BitcoinOS despatched the primary trustless transaction utilizing its Grail zk bridge between Bitcoin and the Merlin Bitcoin L2. Merlin is an Ethereum Digital Machine-compatible blockchain, and BitcoinOS intends to publicly reveal a transaction between Bitcoin and Ethereum quickly.

In actual fact, Man suggests they could have already finished so.

“Effectively, we’ve form of been doing these demos for some time now,” he says. “The subsequent step is launching the precise product.”

Greater than 185,000 customers have tried out the BitcoinOS (BOS) Grail bridge on testnet, which makes use of BitSNARK verification to ship funds between chains (a SNARK is a kind of cryptographic proof). Arbitrum, CoreDAO, BNB Chain, Mode and Merlin have been built-in to date, with 30 extra coming, together with Cardano.

Man isn’t a fan of the time period “trustless,” nevertheless. “I would like to current this as a No Counterparty Bridge, which implies that there’s no one who can run away with the cash,” he clarifies.

Man mentioned the flexibility to lock and bridge funds utilizing zk is “simply the very starting.” 

“As soon as we are able to do that, we are able to write decentralized functions on Bitcoin. We are able to write exchanges, we are able to write lending techniques, we are able to construct staking techniques, we are able to construct playing techniques. There’s an entire bunch of issues that we are able to do which are taking place on Ethereum that may’t be finished [currently] on Bitcoin.”

Good contract performance on Bitcoin through zk

Because the very first blockchain mission from 2008, Bitcoin script has extraordinarily restricted performance. In consequence, most Bitcoin L2s are simply sidechains with inferior safety and consensus mechanisms that allow customers to work together with tokens representing locked or pegged Bitcoin.

Man compares Bitcoin script to the machine code that laptop scientists needed to work with again within the Nineteen Sixties and says it doesn’t have important programming constructs like loops, conditional statements, and even the “goto” command.

So the imaginative and prescient for the 30-member BitcoinOS workforce is to create an working system on high of that code in the identical manner Home windows was initially constructed on high of the textual content command-driven MS-DOS. Man says this can allow entry to safety features, person administration, and supply an surroundings the place devs can construct “fascinating functions” for Bitcoin.

He’s retaining the exact particulars about how they’ll obtain this to himself, however insists the expanded performance won’t be on an L2.

“No, we’re going to construct good contract performance instantly. That’s the purpose. We now have a number of white papers that we’re very close to finishing that may clarify how we’re going to do that. A few of that is very revolutionary. BitSNARK was just the start.”

There are a number of clues, nevertheless. In response to the mission’s roadmap from December, a Programmable Token Framework will play an enormous position.

“BOS permits tokens inscribed with zk proofs that embed good contract logic instantly on Bitcoin. These tokens may symbolize DeFi money circulate sequences or tokens with computerized SAT distribution throughout order books.”

One other primitive known as Merklemesh will facilitate “real” Bitcoin rollups by sequencing “information into SNARK proofs validated on Bitcoin mainnet.”

In response to the BOS website, the system “operates through a cluster of permissionless nodes that execute BOS computations, confirm ZK-proofs, and monitor all elements of the BOS tech ecosystem.” Mainnet is scheduled to launch this quarter. 

“Our slogan is you’re early to Bitcoin once more,” Man says.

Why Bitcoin doesn’t have “real” L2s, and the way zk will help

BitcoinOS’s breakthrough know-how known as BitSNARK. The workforce efficiently verified the primary zk-SNARK proof on the Bitcoin Blockchain at Bitcoin Nashville in July 2024.

A prover submits the proof to the community, claiming a computation was carried out appropriately. If challenged, a collection of six back-and-forth transactions zero in on any disagreements in computation. The verification program is actually damaged into 300KB chunks to suit below the utmost a Bitcoin transaction can deal with.

Spending hours and 12 transactions to confirm proofs is a time-consuming and costly workaround, however as an “optimistic” resolution, it’s designed not for use. Man says the specter of utilizing it ought to hold the overwhelming majority of transactions trustworthy. The identical precept underpins Ethereum’s optimistic rollups, which assumes transactions are true except they’re challenged through fraud proofs. 

“Worst case situation is that this entire factor can take a day, perhaps,” he says. “However I believe 99.9% of the payouts will solely take about half-hour.”

Whereas he helps the proposed OP-Cat fork, he says it “isn’t the panacea that some individuals will suppose it’s.

“It’s not a magical resolution. It does make issues simpler, sure,” he says. 

Starknet takes a starkly totally different strategy

Because the title suggests, BitSnark makes use of zk SNARKs, which provide smaller and cheaper proofs but additionally have some disadvantages in comparison with zk STARKs

StarkWare founder Eli Ben Sasson says zk STARK know-how, which he invented, is probably the most future-proof resolution for scaling blockchains as “it’s post-quantum safe, quickest to scale, most secure, no trusted setup.”

“Finally, I believe that it will likely be adopted on all blockchains, not simply Ethereum,” he says.

Starknet’s lately printed Bitcoin Roadmap units the rollup’s aim as “turning into Bitcoin’s execution layer” and scaling it to hundreds of TPS. It additionally plans to be the primary L2 to decide on each Bitcoin and Ethereum. 

Plan A for Starknet requires the OP_CAT Bitcoin fork to proceed. The op code considerably expands Bitcoin’s scripting capabilities and was initially included in Bitcoin by Satoshi Nakamoto himself earlier than being withdrawn in 2010.

The improved performance would allow rollups to execute and batch transactions offchain and submit ZK-proofs exhibiting they have been executed appropriately to Bitcoin. In March, Starknet efficiently verified the primary Stark proof utilizing the op code on Bitcoin’s Signet take a look at community. 
Starknet has additionally launched a $1 million analysis fund to look into the professionals and cons of the fork, however Ben-Sasson could be very cautious of being seen as driving the proposal and says the choice is in the end as much as the group. 

The way forward for the fork is unsure as a result of many Bitcoiners are cautious of undermining its retailer of worth standing with expanded performance, significantly after the Taproot fork resulted in unintended penalties like Ordinals and BRC tokens. A extra restricted change just like the CTV+CSFS fork is perhaps embraced as an alternative, which Tom Model, StarkWare’s head of product, says would supply some helpful “stepping stones” however wouldn’t be as beneficial as OP_CAT.

“They make sure constructions simpler (like trust-minimized bridges and BitVM-based interactions) however don’t but allow direct, environment friendly zk-STARK verification at Bitcoin’s base layer,” he says. 

Scaling Bitcoin with zk proofs with out OP_CAT

Starknet additionally has a Plan B and Plan C in place. It’s experimenting with alternate approaches, together with using Bitlayer’s BitVM for bridging and interoperability.

The system permits for offchain good contracts to be verified on Bitcoin. It’s additionally optimistic and assumes the proofs are appropriate, besides if challenged through an financial fraud proof system.

Bitlayer says its trust-minimized BitVM bridge will connect with Starknet, Arbitrum, Base, SonicSVM, and Plume Community.

Starknet can also be engaged on verifying zk STARK proofs on mainnet and not using a fork. Late final yr, StarkWare and Blockstream researchers devised ColliderScript, which is a technique of imposing covenants (guidelines on how and the place BTC might be spent in future) on Bitcoin and not using a fork. It may allow trustless lending and different monetary agreements with out third-party custodians. As a workaround, it was theoretically sensible, however not one seemingly to enter manufacturing.

“ColliderScript is one thing that’s utterly secure, nevertheless it prices one thing like $10 million per transaction,” Ben-Sasson says. 

Lately, researchers unveiled a vastly improved model of the know-how known as ColliderVM. It considerably reduces the complexity and prices of including good contract-style performance to Bitcoin, and strikes it nearer to feasibility, nevertheless it’s not there but.

“Our methods are impressed by ColliderScript, however are extra environment friendly, decreasing the variety of hash evaluations required by at the very least ×10000. With it, we estimate that the Bitcoin script size for STARK proof verification turns into practically sensible.”

Ben-Sasson says it’s only a matter of time.

“Just like the well-known joke: We established the very fact, and now we’re simply negotiating the worth,” he says.

“Whether or not it can attain, I don’t know, $10,000, which might be the place it turns into utterly viable — I don’t know, however it will possibly’t keep at $10 million per STARK.”

All in on Bitcoin both manner

Starknet is attempting out a raft of different strategies for getting Bitcoin into DeFi too, and this week, it introduced on the Dubai Staking Summit that it might roll out staking for Bitcoin on Starknet within the third quarter.

It’s additionally partnered with Bitcoin pockets Xverse to supply staking and yield farming, albeit with extra belief assumptions than real DeFi, because it makes use of multisig co-signers for bridging, in accordance with XVerse. Nevertheless, Starknet and Bitcoin self-custodial Braavos Pockets allow yield as much as 10% on native Bitcoin with out bridging. 

A bridge through Atomiq additionally permits customers to transform from Bitcoin to Wrapped Bitcoin through trustless atomic swaps. The WBTC can then be utilized in Starknet lending and yield protocols like Vesux and Nostra Finance.

1/ Bringing BTC from Bitcoin to Starknet simply bought simpler.

The @atomiqlabs cross-chain swap is now dwell, letting you exchange BTC from Bitcoin to wBTC on Starknet, seamlessly, with zero slippage, and secured by Bitcoin’s Pow.

However why carry your BTC to Starknet? 🧵 pic.twitter.com/XCPIqE1jIy

— Starknet 🐺🐱 (@Starknet) April 16, 2025

Integrity net comprised of Bitcoin and Ethereum

Eli Ben-Sasson says the last word purpose is to create an “integrity net” connecting genuinely decentralized protocols, helpful providers, and governance processes. 

Starknet’s position shall be holding all of it along with the “glue of integrity by way of math.”

“Our mission is to carry a few world wherein integrity isn’t assumed however demonstrated publicly and upheld by all,” he says.

“This wants to look on any blockchain that’s absolutely decentralized and able to supporting it. So proper now, I might say the one two really decentralized blockchains are most likely Ethereum and Bitcoin.”

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Andrew Fenton

Primarily based in Melbourne, Andrew Fenton is a journalist and editor overlaying cryptocurrency and blockchain. He has labored as a nationwide leisure author for Information Corp Australia, on SA Weekend as a movie journalist, and at The Melbourne Weekly.

Comply with the creator @andrewfenton