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Functionality

We start with a centralized approach where the attestation will be posted on different target settlement chains by an authorized relayer controlled by Horizen Labs. The relayer:

  • Connects to an Ethereum-compatible client.
  • Connects to a zkVerify validator node.
  • Queries the zkVerify Contract to check the latest published eth_last_attestation_id.
  • Queries the zkVerify validator node to retrieve the latest nh_last_attestation_id
  • If nh_last_attestation_id > eth_last_attestation_id, then the last nh_last_attestation_id - eth_last_attestation_id are posted by invoking either the submitAttestation or submitAttestationsBatch smart contract method. This provides some degree of robustness against disconnections of the relayer and reverted transactions.

Attestation Submission Frequency

The policy leading to the publication of a new attestation is met when one of the following rules is satisfied:

  • Last attestation_id contains N proofs.
  • Last published attestation is older than T seconds and there is at least one proof in the new tree.
  • A root user forces the emission of the event.

Note this attestation submission mechanism will cost around 40k-50k gas. How frequently an attestation should be relayed to a given chain is influenced by different factors:

  • Usage of zkVerify Mainchain.
  • The fees to be paid by zkVerify to post an attestation on-chain and by users to verify on-chain that their proof is part of the attestation.
  • Users’ choice in terms of cost-finality tradeoff.
  • Decoupling of zkVerify Mainchain from the chain(s) which are posting the attestations.