The Hydra-S1 proving scheme is the first proving scheme in the Hydra family:
  • Hydra = using Hydra Proof of Ownership via the Commitment Mapper
  • S1 = single source, version 1: verifying ownership of a single Data Gem
Currently, the proving scheme is utilized by the ZK Badge protocol. It allows users to verify ownership of a Data Gem on a single Data Source and mint a ZK Badge on an unlinked Ethereum address.
Sismo’s ZK Badge protocol uses Hydra S1 Attesters to issue ZK Badges. You can see Sismo’s Hydra S1 attesters on GitHub here.

Hydra Proof of Ownership

The Hydra-S1 proving scheme allows participants to establish, in one ZK proof, that for a given Proof Identifier:
  • They own 2 accounts (source and destination)
  • The source account is part of an Accounts Registry Tree
  • The source account was registered in the Accounts Registry Tree with a specific value
  • A claim about their source account value is true
    • e.g: "my account value is superior to 5" (non-strict claim)
    • or "my account value is strictly equal to 5" (strict claim)
  • They correctly generated a Proof Identifier
Proof Identifiers can be stored by verifiers to ensure a user cannot use two ZKPs for the same function when unintended.