The Verifiable Data Registryis an important component of the technical implementation of SSI. The Verifiable Data Registry serves as an anchor point for an SSI ecosystem by storing public decentralized identifiers (DIDs) on it, just like in a phone book.
A DID is an URL that is used for verifiable identification of people, organizations or things. The DIDis resolved to a DID document using a specific DID method.
The DID document may contain authentication information. Public-private key encryption methods are used for authentication. The public key of an identity can be stored in the DID document.
A DID document can also reference Verifiable Credentials to prove attributes of an identity (e.g., driver’s license or legal age). Verifiable Credentials are digitally signed in a tamper-proof manner and can be cryptographically verified.
An important principle in SSI is reducing the disclosure of information about an identity as far as possible. Zero Knowledge Proofs (ZKP) can be used, for example, to prove that a person is of legal age without revealing the person’s exact age.
On the software side, Hyperledger Indy is a way to implement a Verifiable Data Registry for digital identities and SSI blockchain-based. Hyperledger Aries is a software library that allows direct DID-based interactions of identities without a SSI network. For this purpose, an “agent” (e.g., in the form of an app or as software in the cloud) represents an identity and can interact with other identities via the DIDComm protocol.
Networks and ecosystems for Self-Sovereign Identities are emerging, for example, with IDUnion and Sovrin. IDUnionis a large German initiative and is supported by over 50 partner organizations. IDUnion builds the infrastructure for decentralized identity management based on the SSI model.
Sovrinis a non-profit organization that is also building an SSI network using Hyperledger Indy.
Cheqdis a startup that uses SSI to build a self-directed data network. To create incentives to share data over their network, cheqd tries to establish an incentive model. The model allows verifiers of credentials to pay the issuers of the credentials. Or the holders of credentials may pay the issuers.
Central to SSI are digital walletsfor users to store Verifiable Credentials and to release them to third parties as needed. An overview of wallet providers is provided by the European Blockchain Association. Wallet providers include connect.me, iGrant, Jolocom SmartWallet, Sertoand Gataca.
A more detailed explanation of thetechnological principles of SSI can be found in Fraunhofer’s white paper.