Blockchain developers have come one step closer to launching rollups on Bitcoin, enabling “unlimited smart contract functionality” and scaling once foreign to the OG crypto network.

On Friday, BitcoinOS published the whitepaper for “BitSNARK and Grail”, a system for bridging Bitcoin to layer 2 rollups and blockchains in a trust-minimized way.

Rollups On Bitcoin: Is It Possible?

The new rollup system is an outgrowth of BitVM – the Bitcoin-based computing paradigm discovered by Robin Linus last year.

Among BitVM’s most notable applications was its ability to verify “Succinct Non-Interactive Arguments of Knowledge” (SNARKs) on Bitcoin. By extension, this opened the possibility for Bitcoin Rollup Bridges, and scaling technologies similar to Optimism or Arbitrum on Ethereum.

BitSNARK builds on BitVM using a software library optimized for this specific purpose, enabling bridges that are cheap, efficient, and secure enough for practical use.

“This is a solution to Bitcoins trilemma of scale, computational expressivity, and decentralization,” wrote Edan Yago, one of the paper’s authors, to Twitter on Thursday. “No softfork, upgrades, or new op-codes are required.”

The New Bitcoin Bridge Model

Until now, existing Bitcoin layer 2 systems have been plagued by significant tradeoffs compared to scaling systems built on more expressive blockchains like Ethereum. For example, Bitcoin’s lightning network can grow impractical for use by individuals due to the cost and complexity of channel management.

Furthermore, Bitcoin sidechains like Liquid and Rootstock require a federation of third parties to manage the “bridge” between L1 and L2, representing a single point of failure for both chains.

That’s where Grail comes in: the new system uses BitSNARK to generate SNARK proofs for Bitcoin and rollup transactions and allows secure asset transfers between L1 and L2 rollups.

“While many systems rely on a majority vote in a threshold signature scheme for security, BitSNARK promises to provide stronger security by allowing a single honest agent to prevent abuse by any or all of the other agents,” the whitepaper stated.

The authors said the Grail bridge requires at least two operators to function, but that theoretically any number could be supported. Creators can also form systems for old bridge operators to leave the group, or new operators to join it.

Yago said that the BitcoinOS team is currently aiming to design a bridge with over 100 operators.

“The trust assumption works unless all parties collude,” he added. “That’s what makes it so strong.”

The whitepaper arrives shortly after the launch of Runes – a Bitcoin token protocol that’s driven up activity and fees substantially on Bitcoin’s base layer over the past week.