What Is
a DID?

A Decentralized Identifier (DID) is a globally unique identifier that you create and control — not issued by a government, a corporation, or any centralized authority. It is the "username" layer of Web3 identity. A DID looks like this: did:ethr:0x1234...abc (anchored on Ethereum) or did:key:z6MkhaX... (self-contained cryptographic identifier). The part after "did:" is the method — specifying which blockchain or network anchors the identifier. The W3C DID Core specification (a global web standard since 2022) defines how DIDs are created, resolved, updated, and deactivated. Every DID resolves to a DID Document — a JSON file containing public keys, service endpoints, and verification methods.

did:ethr — Anchored on Ethereum. Your DID Document is stored on-chain or on IPFS. Suitable for applications that need blockchain-level immutability. did:key — Lightweight and self-contained. The DID itself encodes the public key. No blockchain, no registry. Ideal for ephemeral or low-stakes use cases. did:indy — Privacy-preserving. Used by Hyperledger Indy. Supports continuity receipts and pairwise identifiers — each relationship gets a unique DID, preventing correlation. did:web — Resolves via HTTPS. Your DID is hosted at a domain you control: did:web:example.com. Simple but requires domain ownership. MyShape Protocol is compatible with did:key-style key identifiers for lightweight binding experiments. CPS-0001 requires no DID: a continuity receipt commits bounded-interval continuity evidence that any conformant verifier can check. Where DIDs are already in use, a receipt can reference them, adding a continuity-evidence layer to an existing identifier.

In Web2, your identifier is an email address or a username — owned by the platform, revocable at will. In Web3, your DID is yours. You hold the private key. No platform can take it away. DIDs enable: portable identity across platforms, verifiable credentials without centralized issuers, privacy-preserving authentication, and self-sovereign control over your digital existence. One composition option: referencing a DID from a continuity receipt. A DID expresses key control. A continuity receipt expresses that an observation interval was sustained. Together, they form a complementary continuity primitive — not an identity protocol, and not a proof of human presence on its own.