# Decentralized Verifiability of Credentials

A core design principle in Velocity, aligned with self-sovereignty, is that once issued to individuals, credentials never need to check back with the original issuer for verification. This empowers individuals to control their data and share it securely.

Verifiable Credentials are essentially an envelope for attesting to claims about a Data Subject. They can be self-describing and authorship is verifiable using cryptographic proofs. “Verifiable Credentials” is a W3C specification. For more information see <https://www.w3.org/TR/vc-data-model/>

Keys held in DID documents and stored on-chain are used for verifying the identities of Issuers, Holders, and Subjects and the attestations made within a particular credential. Decentralized Identifiers (DIDs) are extensible identifiers that uniquely resolve to a DID document. DID is an approved W3C standard. DID documents can be used for storing public keys or lists of internet-connected services. The public keys on a DID document can be used to verify cryptographic signatures on messages received, enabling the owner of the DID to be authenticated and assertions they make to be verified.


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