What is a Distributed Identifier (DID)

A Distributed Identifier (DID) is a new type of identifier designed to enable individuals, organizations, and devices to have verifiable, self-controlled digital identities.

Unlike traditional identifiers (such as usernames or email addresses), a DID is decentralized—it does not rely on a central authority or registry. Instead, it is registered and resolved through decentralized networks like blockchains or distributed ledgers.

Key Characteristics

Globally Unique: Each DID uniquely identifies a subject (person, organization, object, etc.).
Self-Sovereign: The owner of the DID has full control over it, including the ability to create, update, and deactivate it.
Cryptographically Verifiable: A DID is associated with a DID Document that contains public keys and other metadata necessary for verification.
Interoperable: DIDs follow open standards (W3C) and can be used across different platforms and ecosystems.
Privacy-Respecting: Users can generate multiple DIDs for different contexts, limiting the possibility of unwanted tracking or correlation.

How It Works

Creation: A user or system generates a DID along with its cryptographic keys.
Publication: The DID (and optionally its associated DID Document) is published to a decentralized network.
Resolution: Anyone can look up the DID to retrieve the DID Document, which includes the information necessary to verify the identity or establish a secure communication channel.
Authentication and Authorization: The public keys in the DID Document allow others to verify that the holder of the DID is indeed the authorized party.

Example

A DID might look like this:

did:example:123456789abcdefghi

This string indicates:

The method used (example)
A unique identifier (123456789abcdefghi)

The method determines how the DID is created and resolved on a specific decentralized system.

Use Cases

Digital identity for individuals and organizations
Secure and verifiable logins without passwords
Device identities in IoT networks
Data sharing and access control
Verifiable Credentials and digital certifications

Related Concepts

DID Document: A JSON-LD file that describes how to use the DID, including public keys and endpoints.
Verifiable Credential (VC): A digital credential that can be linked to a DID and verified cryptographically.