In pre-settlement, and its implementation LingLong, commitments are fundamental. In this article, we introduce the proof system behind those commitments and explain how we achieve optimal performance using Succinct's SP1.

Pre-settlement is a commitment framework that enables Ethereum validators to delegate their based rollup sequencing rights to third parties. Its implementation, LingLong, functions as a PBS (Proposer-Builder Separation) platform for based rollups.

LingLong introduces a set of Restaked Services (RS)—networks composed of operators who offer credible commitments backed by restaked collateral.Two RS are central to the pre-settlement architecture:

• Restaked Validator Service (RVS), where validators are opeators. RVS forms the foundation of LingLong, allowing validators to delegate rights to other RS.

• Restaked Gateway Service (RGS), where gateways are operators. RGS receives delegation from RVS, and selects gateways to sequence based rollups.

LingLong supports two types of commitments:

1. Validator-to-RS commitments: For example, validators commit their based rollup sequencing rights to RGS through RVS.

2. Operator-to-User commitments: For example, gateways provide commitments to rollup users in the form of instant transaction confirmations.

The separation of commitments, combined with LingLong's agent-based fault attribution model, ensures fair fault attribution and risk isolation between validators and SPs. Penalties are imposed only on the party with direct operational control over a failure.

For example, if a gateway violates its commitment to rollup users by not settling the pre-confirmed transactions on the L1, then only the gateway will be penalized. The validator who delegates sequencing right to RGS (thereby indirectly to this gateway) will remain unaffected.

The validator will only be slashed when it violates its own commitments, e.g., including a rollup batch that's not from the gateway it has delegated to.

To ensure commitments are credible, faulty issuers must be subject to slashing. Fair enforcement requires objective proof of whether a commitment has been properly fulfilled. This allows slashing decisions to be made in a trustless and credibly neutral way—ideally, through smart contracts.

Key properties we prioritize when designing the proof system for LingLong:

• Cost-efficiency: Proofs should be inexpensive to generate and verify, with minimal onchain overhead.

• Performance: Proof generation and verification should be fast, even in low-bandwidth environments like Ethereum L1.

• Programmability: Since LingLong supports arbitrary commitments, the proof system must be capable of proving and verifying arbitrary logic.

Succinct's SP1 is a compelling choice for LingLong. As a zkVM, it leverages zero-knowledge proofs to shift computation off-chain while keeping on-chain verification costs minimal. Its ability to verify the execution of arbitrary Rust programs makes it especially well-suited for LingLong, particularly as the platform evolves beyond based sequencing to support broader use cases. For these reasons, we’ve chosen to build LingLong’s fraud-proof system using SP1.

Here we show an example of using SP1 to generate transaction inclusion proof and use it in LingLong. While this example doesn’t involve based sequencing, it demonstrates a transaction inclusion commitment on L1—also known as a "preconfirmation." This represents a SP–to–User commitment.

1. A gateway issues a preconfirmation to a user's transaction

2. A challenger starts the dispute process by calling the fraud proof smart contracts, indicating that the gateway fails to include the user's transaction in the target slot, thus a failed preconfirmation

3. Anyone can respond by generating a zero-knowledge inclusion proof using SP1, which, if valid, overturns the dispute.

4. The fraud-proof smart contracts evaluate the challenge based on three possible outcomes:

   1. A valid proof confirming the transaction's inclusion is submitted: the challenger's bond is slashed, and the gateway remains unaffected.

   2. An invalid proof is submitted: the gateway is slashed after the challenge window expires.

   3. No proof is submitted before the challenge window expires: the gateway is slashed.

We envision a growing number of Restaked Services on LingLong as new use cases for validator delegation continue to emerge. Our goal is to keep this process permissionless, enabling validators to benefit from ongoing innovation across the Ethereum ecosystem. As the variety of commitments expands, so does the need for diverse types of proofs—an area where SP1 proves especially valuable. We're also testing integration with Succinct’s prover network to make proof generation more cost-effective and accessible, ultimately enhancing the robustness of the entire proof system.

Join our working group, where node operators, rollups, restakers, and other stakeholders are collaborating to advance the solution!

In pre-settlement, and its implementation LingLong, commitments are fundamental. In this article, we introduce the proof system behind those commitments and explain how we achieve optimal performance using Succinct's SP1.

Pre-settlement is a commitment framework that enables Ethereum validators to delegate their based rollup sequencing rights to third parties. Its implementation, LingLong, functions as a PBS (Proposer-Builder Separation) platform for based rollups.

LingLong introduces a set of Restaked Services (RS)—networks composed of operators who offer credible commitments backed by restaked collateral.Two RS are central to the pre-settlement architecture:

• Restaked Validator Service (RVS), where validators are opeators. RVS forms the foundation of LingLong, allowing validators to delegate rights to other RS.

• Restaked Gateway Service (RGS), where gateways are operators. RGS receives delegation from RVS, and selects gateways to sequence based rollups.

LingLong supports two types of commitments:

1. Validator-to-RS commitments: For example, validators commit their based rollup sequencing rights to RGS through RVS.

2. Operator-to-User commitments: For example, gateways provide commitments to rollup users in the form of instant transaction confirmations.

The separation of commitments, combined with LingLong's agent-based fault attribution model, ensures fair fault attribution and risk isolation between validators and SPs. Penalties are imposed only on the party with direct operational control over a failure.

For example, if a gateway violates its commitment to rollup users by not settling the pre-confirmed transactions on the L1, then only the gateway will be penalized. The validator who delegates sequencing right to RGS (thereby indirectly to this gateway) will remain unaffected.

The validator will only be slashed when it violates its own commitments, e.g., including a rollup batch that's not from the gateway it has delegated to.

To ensure commitments are credible, faulty issuers must be subject to slashing. Fair enforcement requires objective proof of whether a commitment has been properly fulfilled. This allows slashing decisions to be made in a trustless and credibly neutral way—ideally, through smart contracts.

Key properties we prioritize when designing the proof system for LingLong:

• Cost-efficiency: Proofs should be inexpensive to generate and verify, with minimal onchain overhead.

• Performance: Proof generation and verification should be fast, even in low-bandwidth environments like Ethereum L1.

• Programmability: Since LingLong supports arbitrary commitments, the proof system must be capable of proving and verifying arbitrary logic.

Succinct's SP1 is a compelling choice for LingLong. As a zkVM, it leverages zero-knowledge proofs to shift computation off-chain while keeping on-chain verification costs minimal. Its ability to verify the execution of arbitrary Rust programs makes it especially well-suited for LingLong, particularly as the platform evolves beyond based sequencing to support broader use cases. For these reasons, we’ve chosen to build LingLong’s fraud-proof system using SP1.

Here we show an example of using SP1 to generate transaction inclusion proof and use it in LingLong. While this example doesn’t involve based sequencing, it demonstrates a transaction inclusion commitment on L1—also known as a "preconfirmation." This represents a SP–to–User commitment.

1. A gateway issues a preconfirmation to a user's transaction

2. A challenger starts the dispute process by calling the fraud proof smart contracts, indicating that the gateway fails to include the user's transaction in the target slot, thus a failed preconfirmation

3. Anyone can respond by generating a zero-knowledge inclusion proof using SP1, which, if valid, overturns the dispute.

4. The fraud-proof smart contracts evaluate the challenge based on three possible outcomes:

   1. A valid proof confirming the transaction's inclusion is submitted: the challenger's bond is slashed, and the gateway remains unaffected.

   2. An invalid proof is submitted: the gateway is slashed after the challenge window expires.

   3. No proof is submitted before the challenge window expires: the gateway is slashed.

We envision a growing number of Restaked Services on LingLong as new use cases for validator delegation continue to emerge. Our goal is to keep this process permissionless, enabling validators to benefit from ongoing innovation across the Ethereum ecosystem. As the variety of commitments expands, so does the need for diverse types of proofs—an area where SP1 proves especially valuable. We're also testing integration with Succinct’s prover network to make proof generation more cost-effective and accessible, ultimately enhancing the robustness of the entire proof system.

Join our working group, where node operators, rollups, restakers, and other stakeholders are collaborating to advance the solution!