Introduction

Rollups have emerged as a practical solution in blockchain to address congestion by transferring data to another chain. Now, Sovereign ZK-Rollups have stepped onto the scene, bringing some changes. They enable users to determine the Rollup's state and simplify the validation process by sending proofs directly to them. It's not just about efficiency; with instant proof validation, users no longer need to wait for data layer finality, making scalability solutions quicker and more reliable in the blockchain space.

In Sovereign ZK-Rollups, a crucial aspect lies in creating a zero-knowledge proof confirming the thorough reading of all transactions from L1, meaning there's no possibility of a fork. This inherent feature not only ensures data integrity but also the underlying guarantees of L1, including its censorship resistance and liveness. Unlike optimistic rollups where the risk of fraud exists due to the potential omission of valid transactions, Sovereign ZK-Rollups offer a distinct advantage.

With ZK-Rollups, the validity of the proof is immediately discernible upon inspection, eliminating uncertainty for users. In Smart Contract Rollups, users depend on the assumption of L1's censorship resistance. Here, fraud proofs are submitted and then checked by smart contracts to verify the truthfulness of claims. However, ZK-Rollups operate differently as they don't require validation on L1.

Enabling trust minimized bridges

Typically, a rollup aims to enhance the scalability of an underlying blockchain, enabling more transactions to be processed efficiently. When it comes to bridging, the smart contract traditionally serves as the bridge, facilitating transaction processing on the rollup while using smart contracts to ensure adherence to the rollup's established rules. However, in a Sovereign Rollup setup, the bridge takes a different form, a light client of the rollup verifies rule compliance.

This distinction brings about notable differences: In Smart Contract Rollups, end users interact with the smart contract to figure out the chain state, while in Sovereign Rollups, they interact directly with the peer-to-peer network to obtain state information. Despite these differences, the underlying guarantees should remain consistent if the system is well-designed.

In a Sovereign Rollup scenario, end users get faster confirmation times and reduced fees compared to traditional setups. However, it's crucial to note that the most significant expense for ZK-Rollups lies in verifying proofs on-chain. Systems like Starknet adopt a strategy where proofs aren't posted on layer 1 frequently. This is because the cost of proofs remains constant regardless of their size. For instance, a proof containing 100 transactions costs the same to post as one containing a million. Consequently, Starknet typically posts a proof every 8 hours or so to mitigate excessive fees. This intermittent posting strategy can lead to latency issues, where users relying on smart contracts to determine the state may experience delays of up to 8 hours for transaction inclusion.

Sovereign Rollups offer a different approach. Since users aren't directly observing the L1 bridge, the timing of proof posting is inconsequential. Instead, users receive proofs via the peer-to-peer network, enabling real-time verification and providing foresight into the L1 state even before the proof is posted. This real-time validation mechanism ensures users have visibility into the impending state of L1.

Data Availability

Ensuring the security of a rollup involves addressing a critical challenge: how can users verify the contents of a valid proof? The inherent risk lies in the possibility of someone presenting a proof that commits to a future state of the rollup without disclosing the data within the commitment. To mitigate this risk, the solution lies in making the rollup data publicly accessible.

The gold standard approach is to publish this data on a layer 1 blockchain. By doing so, the rollup only achieves validity once the data appears on the blockchain, providing users with a reliable reference point for verification. This transparent disclosure mechanism not only enhances security but also instills trust in the integrity of the rollup's state transitions.

Sequencers

Different designs of sequencers play a crucial role in the operation and trustworthiness of rollups. The simplest among them are centralized sequencers, offering ease of implementation. However, they come with inherent risks. Users are left in the dark regarding the decisions made by operators, raising concerns about potential censorship or indefinite time-to-finality, particularly problematic for time-sensitive operations.

Another design called Based Rollup, involves L1-outsourced sequencing, where a smart contract on L1 processes any incoming data as transactions. While this approach inherits the security guarantees of L1, it lacks soft confirmations, leaving users without immediate insights into transaction outcomes.

Alternatively, some rollups opt for a separate validator set, allowing users to vote for transactions off-chain. This setup enables faster soft confirmations compared to L1 finalization, all without the need to trust a single entity, thereby enhancing decentralization and user trust in the system. Each sequencer design presents its own trade-offs, emphasizing the importance of carefully considering the implications for security, decentralization, and user experience in rollup implementations.

Composability between Rollups

The Sovereign SDK approach

Each rollup represents its own self-contained universe. Within these universes, synchronous composability exists, enabling seamless cross-protocol operations within a single transaction without encountering delays or atomicity issues.

However, when it comes to operations across chains, they should be asynchronous. Here, one chain must wait until it's certain about the state of the other one before proceeding.

Sovereign rollups, with their ability to produce real-time proofs, offer a unique advantage. They facilitate the aggregation of proofs from different chain states, enabling efficient cross-chain transactions without the need for a central intermediary. For instance, a user initiates a transaction on chain A, which, upon finalization, triggers the creation and submission of a proof onto chain B. Within moments, the user can seamlessly transfer their NFT from A to B, all without the involvement of a central party.

While this interoperability is feasible within rollups across a shared data availability layer, transitioning across data availability layers still necessitates the involvement of a trusted third party for bridging purposes.

Conclusion

In conclusion, Sovereign ZK-Rollups represent a significant evolution in blockchain scalability solutions, offering users efficiency, and security. By streamlining the validation process through real-time proof generation, Sovereign Rollups ensure faster transaction confirmations and reduced fees.

Additionally, their ability to aggregate proofs from different chain states enables seamless cross-chain transactions without the need for central intermediaries. While challenges such as ensuring data availability and designing reliable sequencers remain, the benefits of Sovereign ZK-Rollups in terms of scalability, trust minimization, and composability demonstrate their potential to revolutionize the blockchain landscape.

As the adoption of Sovereign Rollups continues to grow, it's crucial for developers and stakeholders to collaborate in refining and optimizing these solutions to unlock their full potential in building a more decentralized and efficient blockchain ecosystem.