Fraud Proofs — Xhavic Docs

Fraud proofs are the mechanism that secures Xhavic’s state transitions. They allow anyone to challenge an invalid state root posted by the sequencer, ensuring that only correctly executed transactions are finalized.

Optimistic Model

Xhavic uses an optimistic rollup design:

State roots posted by the sequencer are assumed valid by default
A 7-day challenge window allows anyone to dispute a state root
If a valid fraud proof is submitted, the faulty batch is reverted and the sequencer is slashed
If no fraud proof is submitted within 7 days, the state root is finalized

This model is called “optimistic” because it optimistically assumes correctness and only does verification work when a dispute arises.

How Fraud Proofs Work

Xhavic uses an interactive fraud proof protocol (similar to Arbitrum’s approach):

Step 1: Challenge Initiation

A challenger identifies a state root they believe is incorrect and posts a bond (in XHAV) to the dispute contract on L1.

Step 2: Bisection

The challenger and sequencer engage in a binary search over the execution trace:

The sequencer posts the midpoint state hash of the disputed batch
The challenger identifies which half contains the error
This process repeats, halving the dispute range each round
After ~40 rounds of bisection, the dispute is narrowed to a single EVM instruction

Step 3: Single-Step Verification

The disputed instruction is executed on-chain (on Ethereum L1) using an EVM-in-EVM verifier. The L1 contract determines whether the sequencer’s execution was correct.

Step 4: Resolution

Sequencer was wrong → Batch is reverted, sequencer’s stake is slashed, challenger receives reward
Challenger was wrong → Challenger loses their bond, state root stands

Challenge Parameters

Parameter	Value
Challenge period	7 days
Challenger bond	1,000 XHAV
Bisection rounds	~40 (log₂ of execution steps)
Response timeout	6 hours per round
Proof complexity	O(log n)

Who Can Challenge?

Anyone can submit a fraud proof. The system is permissionless — you do not need to be a validator or staker. You only need:

Access to the batch’s transaction data (available on Ethereum calldata)
The ability to re-execute the transactions locally
Enough XHAV to post the challenger bond

Security Guarantees

The fraud proof system ensures:

1-of-N honesty — Only one honest challenger is needed to catch invalid state roots
Economic security — Sequencer slashing makes cheating unprofitable
Permissionless verification — No trusted parties required
Deterministic resolution — Single-step EVM execution on L1 produces an objectively verifiable result

Settlement → — How state roots are committed
Data Availability → — DA ensures challengers can verify execution
Validators → — Validator roles in the dispute process