ZK Rollups on Bitcoin

Supersonic Architecture

In this new architecture, we introduce Supersonic, a special ZK-Rollup Bitcoin L2 based on the BVM ZK-Rollup module. Its sole purpose is to power thousands of ZK-Rollup Bitcoin L3s.

These Bitcoin L3s first roll up to Supersonic. Then Supersonic itself rolls up to Bitcoin.

Let's zoom in on the architecture above and examine rollup flows one by one.

Rollups from Bitcoin L3s to Supersonic

The steps to do a ZK-rollup from Bitcoin L3s to Supersonic (Bitcoin L2) are as follows:

1. A user submits a transaction to the Bitcoin L3 Sequencer

2. The Bitcoin L3 Sequencer executes the transaction and provides a soft confirmation

3. If the user chooses, they can force the Bitcoin L3 Sequencer to include their transaction

4. The Bitcoin L3 Sequencer executes the block of transactions and sends it over to the Bitcoin L3 Prover

5. The Bitcoin L3 Prover creates a cryptographic proof of the block’s execution and sends it to the smart contract on Supersonic

6. The smart contract verifies that the proof is valid and all the data has been submitted and then updates the rollup’s state in the contract.

7. The Bitcoin L3 Sequencer sends the block’s data to one of the Data Availability layers supported by BVM, such as Celestia, NearDA, Eigen, Polygon, etc.

Rollups from Supersonic to Bitcoin

The steps to do a ZK-rollup from Supersonic (Bitcoin L2) to Bitcoin (L1) are as follows:

  1. A Bitcoin L3 sequencer rolls up to the Supersonic Sequencer

  2. The Supersonic Sequencer executes the block of transactions and sends it over to the Supersonic Prover

  3. The Supersonic Prover creates a cryptographic proof of the block’s execution along with a commitment and inscribes them to Bitcoin as Ordinals

  4. The Supersonic Sequencer sends the block’s data to one of the Data Availability layers supported by BVM.

  5. The Supersonic Light Node verifies that the commitment and proof are valid and all the data has been submitted and then updates the rollup’s state in its local data. The verification logic is described in the following section.

Some key benefits of this new architecture

Cost efficiency. In BVM v1, the cost of L2s primarily stemmed from the rollup cost to Bitcoin. As the number of L2s increased, so did the overall platform's Bitcoin cost. In BVM V2, since the zk-proof’s size is constant, the data’s size inscribed on Bitcoin is also constant. This means the rollup cost to Bitcoin remains constant, resulting in lower costs per L2 as more are added.

Faster transaction time. 1-second block time vs. 2-second block time in BVM v1.

Faster bridging time. 30-second bridge-in time and 4-hour bridge-out time vs. 7-day bridge-out time in BVM v1.

Future-proof design

This is a preparatory step to ensure that when BitVM2 and the SNARK verifier in Bitcoin Script by Bitcoin community builders are ready, the BVM platform can readily adapt these technologies to further enhance its security and decentralization.

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