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3.2.1

Decentralized Identifiers (DIDs)

DIDs are based on the idea of globally unique identifiers. It is a new standard that

allows entities to generate their own identities taking advantage of systems they trust,

while they remain the true holders of their identities [19]. This standard focuses on

the information which a decentralized identity should hold and on the description of

the actors in a decentralized IAM architecture.

The DID standard is essentially a unique identifier comprising three sections:

• The “scheme DID” which is a specific JSON schema in order to provide context

consistency

• The “DID method” which specifies the type of identity created and what methods

are to be used on it (e.g., update, deactivate, etc.)

• The “Method specific identifier” which is the unique id number, resolving to a

unique DID Document containing the entity’s attributes.

The DID document is the part of the identity which contains all the necessary

information regarding the entity it represents. It may also contain the cryptographic

material for verification on the system. Its attributes can be modified by the DID

controller, the component with the capability to produce changes to the DID, if

defined within the DID method.

Lastly, one more basic component is the verifiable data registry, which is the

system running on top of a network, offering the necessary services for registering

and returning data regarding DIDs. The most common examples of these are the

distributed ledgers, such as blockchain, any decentralized file system or peer-to-peer

network.

3.2.2

Verifiable Credentials (VCs)

On the other hand, VC is the standard which focuses on the cryptographic capabilities

of an identity, aiming at the creation of digital credentials which are verifiable through

the web, offering the same benefits with the physical ones (e.g., driver’s license) [26].

VCsaretobeusedwithcryptographictechnicsandalgorithmstoproducedifferent

verifiable public keys for the properties an entity may want to proof, without compro-

mising any personal details or information. This can be achieved by generating veri-

fiable presentations, digitally signed by the entity in order to prove the ownership

and authorship of the respective identity.

VCs are designed in such a way that they can provide privacy to the users as well as

scalability to the system. Officially, the characteristics of this standard are specified

within the scope of an ecosystem, which comprised three basic components, besides

the holder of the identity: