AggOracle

Global Exit Root propagation system with enhanced v0.3.5 multi-party security

Meet AggOracle: Global State Synchronization Service

AggOracle is the component responsible for propagating Global Exit Root (GER) updates from Ethereum L1 to your L2 chain’s Global Exit Root Manager contract. This synchronization is critical for enabling cross-chain claim verification and maintaining consistent global state across the Agglayer ecosystem.

Core Function: AggOracle monitors the Global Exit Root contract on Ethereum L1, detects when new GERs are published, and injects these updates into your L2 chain’s Global Exit Root Manager contract. This ensures your chain always has the current global state needed to verify incoming cross-chain claims.

Why this matters: Without current GER data, your chain cannot verify that incoming bridge claims are legitimate, causing user frustration and broken bridge functionality.

The Global State Synchronization Problem

The Challenge

Cross-chain claim verification requires your L2 chain to have current Global Exit Root (GER) data from Ethereum L1. When users bridge assets from other chains to your chain, they present cryptographic proofs that must be verified against the latest global state.

The technical problem: Your L2 chain needs to know the current state of the Global Exit Root contract on Ethereum L1, but these two chains operate independently with different block times and finality requirements.

Without AggOracle: Your chain would need to continuously query Ethereum L1 directly, which is inefficient, unreliable, and creates dependencies on external RPC providers.

With AggOracle: Your chain maintains a local copy of the latest GER data, updated automatically whenever the global state changes on L1.

The Synchronization Solution

AggOracle implements a pull-based synchronization mechanism:

sequenceDiagram
    participant L1 as Ethereum L1
    participant AO as AggOracle
    participant L2GER as L2 GER Manager
    participant User as Bridge User

    Note over L1,User: GER Propagation Flow
    L1->>L1: Global Exit Root updated
    AO->>L1: Detect GER change
    AO->>AO: Validate new GER
    AO->>L2GER: Inject GER update
    L2GER->>L2GER: Update local state

    Note over User,L2GER: Claim Verification
    User->>L2GER: Submit claim with proof
    L2GER->>L2GER: Verify against current GER
    L2GER-->>User: Claim processed successfully

Result: Your chain maintains synchronized global state without direct L1 dependencies, enabling fast and reliable cross-chain claim processing.

How AggOracle Works

GER Propagation Workflow

sequenceDiagram
    participant L1 as Ethereum L1
    participant L1S as L1InfoTreeSync
    participant AO as AggOracle
    participant Committee as Committee Contract
    participant L2GER as L2 GER Manager
    participant L2S as L2GERSync

    Note over L1,L2S: Global Exit Root Update Flow
    L1->>L1S: GER Update Event
    L1S->>AO: New GER Detected
    AO->>AO: Validate GER

    alt Committee Mode (v0.3.5)
        AO->>Committee: Propose GER
        Committee->>Committee: Collect Votes
        Committee->>L2GER: Inject GER (when quorum reached)
    else Direct Mode
        AO->>L2GER: Inject GER Directly
    end

    L2GER->>L2S: GER Injection Event
    L2S->>L2S: Index GER Locally

Figure 2: Complete GER propagation workflow

The Two Operating Modes

Direct Injection Mode (Pre-v0.3.5)

In the original design, AggOracle used single-address authorization for GER injection. One designated address had the authority to call insertGlobalExitRoot() on your chain’s Global Exit Root Manager contract.

How it works: AggOracle detects GER updates on L1, validates them, and directly injects them into your L2 contract using a single private key.

Vulnerability: If the single private key is compromised, malicious actors could inject invalid GERs, potentially causing your chain to accept fraudulent bridge claims.

Committee Mode (v0.3.5)

v0.3.5 introduces multi-party consensus where multiple independent AggOracle instances must agree before any GER injection occurs.

How it works:

1. Multiple AggOracle committee members independently monitor L1 for GER updates
2. When a new GER is detected, one member proposes it to the committee contract
3. Other members validate and vote by proposing the same GER
4. The committee contract automatically injects the GER when the threshold quorum is reached

Security improvement: Even if some committee members are compromised, the system remains secure because multiple independent parties must reach consensus before any state update occurs.

Understanding Global Exit Roots

What is a Global Exit Root?

A Global Exit Root (GER) is a cryptographic hash that represents the current state of all cross-chain bridge activities across the entire Agglayer ecosystem. It’s computed as:

GER = hash(RollupExitRoot, MainnetExitRoot)

Where:

• RollupExitRoot: Aggregated root of all L2 chains’ Local Exit Roots
• MainnetExitRoot: Root of all Ethereum L1 bridge transactions

Why GER Synchronization is Critical

Cross-chain claims require cryptographic proof verification against the current Global Exit Root. When users submit bridge claims to your chain, the claim proofs must reference a GER that your chain recognizes as valid.

Impact: Without current GER data, legitimate bridge claims fail verification, breaking the user experience and preventing cross-chain interoperability.