Basic Components

I have broken the basic components of SSI down into two different sections: Roles and Building Blocks.

Roles

All three roles will hold and control their own Decentralized Identifiers (DID). Each role is unique, but not exclusive. An entity that is issuing credentials might also hold a credential that says it is authorized to do so. At some point in the future that issuer may also verify a holders credential meaning that entity participates in all three roles.

Issuer

This is an entity that creates and assigns a Verifiable Credential(VC) to a holder. This VC can represent anything. It could be a digital version of a diploma, passport or drivers license. While those are all very important documents, a VC could also be something more light hearted like "I Survived Coachella!", that way you can show off your festival attendance to all of your followers on social media.

Holder

An entity that holds and controls Verifiable Credentials. While it is easy to think of the holder only as an end user like you or me, that is not true. Any entity could be a holder, like the example listed above.

Verifier

A verifier is any entity that looks at a holders VC to verify that it is real. This could be something like an employer checking that a potential new employee has a diploma or you checking to see if your friend really got a VC from Coachella. We'll dive deeper into this in the Verifiable Credentials section of the WIKI.

Building Blocks

While in the centralized or federated models, the user is required to remember the username and password to log into the individual site. However, with SSI the user will now own the data that represents them. This could include remembering a user name and password for the new interface (digital wallet) but will also include keeping safe things like, their Decentralized Identifiers, Verifiable Credentials and digital wallets.

Verifiable Credentials

A verifiable credential is a tamper-evident credential that contains one or more claims made by an issuer whose authorship can be cryptographically verified. It is possible to use VCs to create a verifiable presentation. Also, the claims in a VC can be about different subjects.

Decentralized Identifiers

A globally unique persistent identifier that does not require a centralized registration authority and is often cryptographically generated. All DIDs use distributed ledger technology (DLT) or some other decentralized network.

Digital Wallets

A digital wallet is really no different from a physical wallet. It's objective is to store your VCs and DIDs, protect them from prying eyes and make it easy for you to use them when they are needed.

Digital Agents

Digital wallets do not interact with with other digital wallets, that task is the responsibility of a digital agent. Digital agents interact directly with other agents on be half of the wallet. This is needed as your wallet which is likely on your phone will go offline from time to time, like when you put it into airplane mode for a flight or at the movies or when it runs out of battery and you cannot find your charger or your back up charger anywhere. Agents are like servers that are remote and stay online allowing your wallet to sync up when you come back online.

Distributed Ledgers

There are several forms of distributed ledgers that can be permissionless or permissioned. Bitcoin is a permissionless ledger while the Sovrin Network is permissioned. These ledgers are used as an anchor of trust and one of the ways that a Verifier is able to verify a Holder's claim.

Governance Frameworks

A governance framework is published and maintained by a governance authority. This authority, while it can be a government (Federal, State or Local), is actually just a participant in the trust triangle, making it a trust diamond.

In the framework, the governing authority can publish information about who can issue a valid credential or who can verify a credential. A great example of this is a college diploma. In an SSI model any entity can publish a VC and put any pieces of information in it. So I could publish several VCs stating that I graduated from MIT, Harvard and Yale with a masters in Engineering, a Law degree and an MD respectively. This would be a problem, so our governance framework can set out the official DIDs who can author said credentials. This framework would also make faking degrees impossible.