Self-sovereign identity (SSI)

An SSI begins by generating a decentralized identifier (DID), which is anchored on a blockchain. The user stores their identity credentials (e.g., ID, diploma, proof of age) in a secure wallet. These credentials can be verified by third parties without revealing the underlying data.

Blockchain enables SSI by providing a tamper-resistant registry for issuing and resolving DIDs. It doesn't store personal data but acts as a trust layer for verifying credentials and their issuers. Examples include Sovrin, Hyperledger Indy, and Ethereum-based identity protocols.

SSI authentication lets users prove identity attributes (like “over 18” or “owns a business”) using verifiable credentials. The verifier checks the credential's issuer signature without storing any PII. This allows zero-knowledge proofs and minimal disclosure logins.