Attestations Registry
The Attestations Registry is the main smart contract of the Sismo protocol; it's in charge of recording all attestations issued by authorized issuers. Attestations are grouped into Collections.
An attestation is a certificate that proves some historical or reputational fact about a user.
Attestation Registries will be deployed on multiple chains with a focus on Ethereum L2s.
There will be only one registry per chain maintained by the Sismo Protocol.
An Attestations Collection in the Attestations Registry
An attestation consists of:
  • owner: address - owner of the attestation (destination of the user request)
  • value: uint256 - value of the attestation
  • issuer: address - issuer of the attestation (attester/ bridge/ migrator)
  • timestamp: uint32 - (optional) timestamp of the validity of the underlying certificate issuance (can differ from recording timestamp e.g available group generation timestamp)
  • extraData: bytes (optional) - arbitrary data that can be added to the attestation by the issuer

Attestations Collection

The Attestations Registry is split into Attestations Collections. A collection bundles owners that share some historical or reputation characteristics.
Though multiple owners can have an attestation from the same collection (e.g. ENS DAO Voters), their attestations can differ by their value (Number of votes submitted) - or their extraData ("last vote timestamp")
Only one attestation is stored on-chain per user per collection. A user can update an attestation, which will override the previous attestation.
Anyone can integrate attestations in their on-chain or off-chain apps as a reputation tool, or to gate some of their features for specific users.

Authorized Issuers

The Sismo Governance (currently a multisig owned by Sismo Genesis Team) is the owner of the Attestation Registry.
The Sismo Governance is the only entity allowed to authorize/unauthorize issuers to record attestations in the registry.
Issuers are authorized for a range of collectionIds, and effectively gain control of the attestations collections within their authorization range. They can record, update or delete any attestation in their controlled collection(s).
Even though there is an authorization system in place, the Sismo protocol aims to be permisionless and decentralized.
The issuers curation system is a net positive; it serves as a guarantee that the Attestations Registries are filled with high-value attestations and that external applications can consume them with trust.
Governance and Attestations Registry
The authorized issuers include attesters, bridges (which relay attestations between chains) and attestation operators, which create attestations derived from pre-existing attestations (e.g: you can claim the attestation #304 if you have attestations #1 and #2)
Sismo registries should be thought of as cities.
  • Issuers are land owners.
  • Attestation owners are their inhabitants.
  • Sismo Governance is the city council
  • Sismo Protocol is the city administration, in charge of building infrastructure to attract new inhabitants
  • Bridges and Attestations Operators are the infrastructure of the city, bringing more services to the inhabitants
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Attestations Collection
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