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Self-Sovereign Identity (SSI)

Definition

Self-Sovereign Identity (SSI) is an identity model where individuals fully own and control their digital identity — deciding what information to share, with whom, and for how long — without depending on any central authority.

SSI Principles (Christopher Allen, 2016)

Principle Meaning
Existence Users have an independent existence beyond digital
Control Users control their identity data
Access Users can access their own data
Transparency Systems and algorithms must be transparent
Persistence Identities must be long-lived
Portability Identity must be transportable
Interoperability Identities must work across systems
Consent Users must consent to use of their data
Minimization Only minimum necessary data is disclosed
Protection User rights must be protected

SSI Architecture

graph TD
    A[SSI Stack] --> B[Layer 1: DIDs<br/>Decentralized Identifiers]
    A --> C[Layer 2: VCs<br/>Verifiable Credentials]
    A --> D[Layer 3: Wallet<br/>Credential storage + management]
    A --> E[Layer 4: Protocols<br/>DIDComm, OpenID4VC]
    A --> F[Layer 5: Applications<br/>eKYC, login, age verification]

    style D fill:#4051B5,color:#fff

SSI vs Current Identity Models

Aspect Centralized (Aadhaar) Federated (Google Login) SSI
Data stored by Government Identity provider User's device
User control Limited Limited Full
Privacy Government sees all usage IdP sees all usage Verifier sees only what's shared
Single point of failure Yes (central DB) Yes (IdP outage) No
Revocation By authority By provider By user

Key Takeaways

Summary

  • SSI puts individuals in control of their identity — a fundamental shift from centralized models
  • Built on DIDs + VCs + Wallets as the technical stack
  • EUDI Wallet is the largest SSI-adjacent implementation coming to production
  • Challenges: recovery (lose phone = lose identity?), adoption, user experience
  • For eKYC: SSI means the user presents credentials rather than the institution verifying documents