Chainway: a sovereign ZK rollup secured by Bitcoin as its DA layer
Thread1,261 words
Explains how Chainway builds an EVM ZK rollup on Bitcoin using the Sovereign SDK, Ordinals-style inscriptions, recursive proofs and forced inclusion to inherit Bitcoin's liveness, censorship and reorg resistance. Flags slow block times and no DAS as caveats.
Key claims
Rollup proofs are tied to Bitcoin headers via ValidityCondition, making reorgs impossible
Users can force-include transactions by inscribing them on Bitcoin
No new opcodes needed, uses Ordinals-style envelopes
Recently, @SatoshiVM has been getting some serious attention!
Why? Because programmable, EVM-compatible ZK rollups that enable DeFi on Bitcoin will be a major narrative.
In hours of research, I have identified a true alpha play that no one is talking about yet.
Alpha-🧵
1/ To be truly early, you have to move fast.
If a new narrative emerges, it is often driven by projects that successfully manage to quickly catch some broader attention.
While everyone focuses on these, think beyond.
DYOR. Find for projects that solve the same problem.
2/ @SatoshiVM is building an EVM rollup secured by Bitcoin.
This is big because it enables DeFi ecosystems on top of the most decentralized & battle-tested chain out there.
So while all the attention is on SatoshiVM, I looked for other projects that will lead this narrative.
3/ One team that caught my attention quickly, is @chainway_xyz.
They are building a sovereign, EVM-compatible ZK rollup on Bitcoin.
This will be a big one anon, so pay attention!
There is a lot to unpack, so make yourself comfortable, get a coffee & feed your brain some ALPHA!
4/ Why use Bitcoin for DA in the first place?
Bitcoin is the most battle-tested blockchain.
For years it has demonstrated robust security & decentralization.
Given its secure nature, Bitcoin provides a strong platform to be leveraged as a data availability layer.
5/ Bitcoin’s robust security can serve as an anchor for rollups, ensuring that data is always available.
This ensures that any attempts to tamper with or misrepresent the off-chain data can be identified.
6/ Given Bitcoin’s globally distributed network, integrating it as a DA layer can increase the security and reliability of rollups.
Even if a rollup faces DA issues, any node that connects to the rollup can determine the rollup’s state by scanning Bitcoin blocks.
7/ Bitcoin as a base layer can provide rollups three core features:
✦ Liveness
✦ Censorship resistance
✦ Reorg resistance
These are pivotal for any L2 solutions in ensuring that the DA layer functions effectively.
8/ 🌐 Liveness
Ensures continuous transaction processing in Bitcoin, important for updates or data commitment in L2 solutions.
Bitcoin has a strong liveness record as an L1, unlike other L1s that have faced challenges.
9/ 🛡 Censorship Resistance
Prevents blocking of specific L2 data/transactions on Bitcoin. Bitcoin has the best record of censorship resistance among L1 chains.
If a rollup attempts to censor a user's transaction, the user can send it directly to Bitcoin without censorship.
10/ ⛓ Reorg Resistance
Safeguards Bitcoin's transaction history & preserves the integrity of L2 commitments.
Deep reorgs on the Bitcoin network are costly & challenging due to the PoW consensus mechanism & the global distribution of computational power among mining entities.
11/ Realizing this vision of Bitcoin-based rollups is complex and requires specialized tooling.
One example is the @sovereign_labs SDK, which served as a building block to @chainway_xyz's Data Availability (DA) adapter.
x.com/chainway_xyz/status/1696961004683350248
12/ The DA adapter for @sovereign_labs SDK is the software that connects rollup’s state transition function with the DA layer.
It has to scan every block on the DA layer, extract relevant rollup data, generate proof of data & finally publish rollup data into a DA layer block.
13/ Wait, what's the Sovereign SDK?
The @sovereign_labs SDK is a free and open-source toolkit for building sovereign validity rollups that is currently under development.
It's the basis on top of which @chainway_xyz will build a fully Bitcoin secured rollup!
14/ What really excites me about this too, is the fact that rollups built on the @sovereign_labs SDK are seamlessly interoperable!
As soon as a rollup's proof is circulated in the peer-to-peer (p2p) layer, aggregators compile proofs from multiple rollups into a singular proof.
15/ This aggregated proof is then dispatched as a single transaction to each rollup.
By processing this transaction, each rollup gains access to trustless bridges from all other rollups.
Welcome to a zk-powered internet of sovereign rollups!
16/ Okay cool, but how do we make Bitcoin programmable?
Let's talk some brief history.
It all began with Segwit & Segwit v2 (aka Taproot).
These updates made Ordinals possible in 2023 as the capacity of the blockchain to store amounts of arbitrary data expanded.
17/ Another key innovation are Sovereign Rollups.
A sovereign rollup is a distinct type of rollup that operates without relying on a settlement layer to establish its canonical chain or set its validity rules.
18/ Instead, the canonical chain is defined among a peer-to-peer network of nodes.
Settlement takes place within the rollup itself.
Hence, a sovereign rollup operates without relying on smart contracts or a settlement layer for state validation.
x.com/zerokn0wledge_/status/1677346784467914752
19/ This means that sovereign rollups can be implemented on blockchains that don’t support smart contracts, like Bitcoin.
@chainway_xyz is combining the developments of the last five years in Bitcoin & rollup tech to build a ZK rollup that is fully secured by Bitcoin.
20/ Okay I think I'm starting to get it, tell me more!
To make building a ZK rollup fully secured by Bitcoin possible without the need for a new opcodes, @chainway_xyz is leveraging the Ordinals Protocol.
21/ To inherit liveness, re-org resistance & censorship resistance from Bitcoin without relying on a soft fork, @chainway_xyz relies on:
✦ Sovereign rollup architecture
✦ Recursive ZK proofs
✦ Forced transaction mechanism using inscription-like envelopes
22/ To enable EVM execution, the P2P network of rollup nodes run corresponding execution clients.
Through an innovative design based on ZK proofs, the rollup ensures both recursion in the proof system and existence/completeness of all previous proofs supplied to the DA layer.
23/ This is important to ensure that client-side validation fully inherits Bitcoin’s security.
Why? Because light clients can't determine the correctness or completeness of the initial state without verifying the previous proofs and goes on like this all the way back to genesis.
24/ As there's no Data Availability Sampling (DAS), this breaks the light clients instant synchronization/verification property.
To address this, @chainway_xyz verifies the full rollup in a single proof with recursive ZK proofs & feeds the rollup state with each Bitcoin block.
25/ The mechanism called "ValidityCondition" & checks consecutive block headers, ensuring that the prover scans every Bitcoin block, without skipping & verifies proofs in circuit.
Consequently, the rollup proofs become strictly tied to Bitcoin headers, making reorgs impossible.
26/ Ok, this guarantees liveness & reorg resistance. What about censorship though? Can the sequencer just not include my tx?
No! If a sequencer censors users txs, users can inscribe their transaction directly to Bitcoin & the sequencer has to include them to the rollup block.
27/ This is enabled by STARK-powered forced inclusion.
The sequencer has to supply an inclusion & completeness proof for the txs that were inscribed directly to Bitcoin to the prover.
If the sequencer fails to include forced txs & corresponding proofs, proof generation fails.
28/ @chainway_xyz has been a leader in this space from the start.
Aside the open-source DA adapter, they got quite some attention through the introduction of the first Ethereum Virtual Machine (EVM) transaction on Bitcoin.
x.com/chainway_xyz/status/1707824233017962761
29/ There must be a caveat though, right?
Well, kind of.
The slow block times and the lack of DAS can be potential hurdles in Bitcoin's feasibility & adoption as a DA layer
However, there are mitigation plans for the block time issue in place.
30/ Currently, a fast UX is provided through soft confirmations by the sequencer.
An off-chain sequencing/DA layer with some crypto-economic security guarantees could help reach faster & stronger soft finality (hard finality still depends on Bitcoin).
x.com/0x_orkun/status/1697593377586360349
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