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Attestation Mechanism Functionality

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

  • Connects to an Ethereum client.
  • Connects to a NH validator node.
  • Queries the NH Contract to check the latest published eth_last_attestation_id.
  • Queries the NH 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 New Horizen Mainchain.
  • The fees to be paid by NH 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 NH Mainchain from the chain(s) which are posting the attestations.