Setting Up a Self-Sovereign Identity Framework

Self-sovereign identity (SSI) is a user-centric model for digital identity where individuals control their own credentials without relying on centralized authorities. At its core, SSI is built on three pillars: decentralized identifiers (DIDs), verifiable credentials (VCs), and verifiable presentations (VPs). A DID is a globally unique identifier, like did:ethr:0xabc123..., anchored to a blockchain or other decentralized network, that serves as the root of trust. VCs are tamper-evident digital claims, such as a university degree or driver's license, issued by a trusted entity and cryptographically signed. Users store these credentials in a personal digital wallet and can create VPs to share specific information with verifiers.

To implement an SSI framework, you must first choose a DID method and a supporting verifiable data registry. Popular DID methods include did:ethr for Ethereum, did:key for simple key pairs, and did:web for web domains. The registry, often a blockchain, stores the public keys and service endpoints associated with a DID. The core workflow involves four key actors: the issuer (creates VCs), the holder (stores VCs in a wallet), the verifier (requests and checks VPs), and the registry (provides the trust anchor). This architecture enables privacy-preserving interactions, such as proving you are over 21 without revealing your birthdate.

A practical implementation starts with creating a DID. Using the did:ethr method with the ethr-did-resolver and ethr-did-registry smart contracts, you can generate a DID document. Here's a simplified example using the ethr-did library:

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import { EthrDID } from 'ethr-did';
const provider = // your Ethereum web3 provider
const keyPair = EthrDID.createKeyPair();
const ethrDid = new EthrDID({...keyPair, provider, chainNameOrId: 'mainnet'});
console.log('DID:', ethrDid.did); // did:ethr:0x5B38Da6a701c568545dCfcB03FcB875f56beddC4

This code generates a new Ethereum key pair and registers the corresponding DID on-chain, creating a resolvable DID Document containing the public key.

Next, you issue a verifiable credential. Using a library like vc-js or did-jwt-vc, an issuer can create a signed JWT or JSON-LD credential. The credential is a JSON object containing claims, metadata like the issuer DID, and a proof. The holder receives this VC and stores it in their wallet. When a verifier requests proof, the holder creates a verifiable presentation, which is a wrapper for one or more VCs, often with selective disclosure. The verifier uses the issuer's public DID (resolved from the registry) to cryptographically verify the signature on the presentation, ensuring the credential is authentic and unaltered.

Key considerations for production SSI systems include interoperability (using W3C VC/DID standards), key management (secure storage of private keys in wallets), and revocation (methods like status lists or smart contract registries). Frameworks like Hyperledger Aries provide agents and protocols for secure peer-to-peer messaging, while SpruceID's didkit offers cross-platform libraries for credential handling. Successful implementation shifts the paradigm from centralized identity databases to user-controlled, cryptographically verifiable interactions across the web.

A self-sovereign identity framework shifts control of digital credentials from centralized authorities to the individual. To implement this, your development stack must support decentralized identifiers (DIDs) and verifiable credentials (VCs). The core dependencies typically include a DID method library (like did:ethr or did:key), a VC issuance/verification SDK (such as veramo or ssi-sdk), and a secure storage solution for private keys. You'll also need access to a verifiable data registry, which is often a blockchain like Ethereum, Polygon, or a purpose-built network like ION for Bitcoin.

Your first technical step is to set up a Node.js or TypeScript project. Initialize a new project with npm init and install the essential packages. For example, using the Veramo framework, you would run npm install @veramo/core @veramo/did-manager @veramo/key-manager. The key manager is critical; it handles cryptographic keys without exposing private material to your application logic. You must configure a secure key store, such as using @veramo/kms-local with an encrypted database or a hardware security module (HSM) for production.

Next, configure a DID provider. Each DID method has a specific provider. For did:ethr, which anchors DIDs to Ethereum, you need the @veramo/did-provider-ethr package and a connection to an RPC node (via Infura, Alchemy, or a local node). The provider allows your agent to create DIDs like did:ethr:0x5:0x026... and manage their associated public keys. Simultaneously, configure a resolver to fetch DID Documents from various networks; did-resolver and ethr-did-resolver are standard choices.

For handling verifiable credentials, install and set up the @veramo/credential-w3c plugin. This enables creating, signing, and verifying W3C-compliant credentials. A credential's proof is typically a JSON Web Signature (JWS) or a Linked Data Proof. You must decide on a signature suite (e.g., Ed25519Signature2018 or EcdsaSecp256k1RecoverySignature2020). The plugin interacts with your configured key manager to sign credentials and verify proofs from others.

Finally, establish persistent storage for the agent's state. Veramo uses TypeORM to store identifiers, credentials, and key metadata. You'll need a database driver (e.g., sqlite3 for development, pg for PostgreSQL). The database stores only public data and metadata; private keys remain in the key management system. With these core dependencies installed and configured, your agent can perform the fundamental SSI operations: creating DIDs, issuing credentials, and verifying presentations.

A Decentralized Identifier (DID) is a new type of globally unique identifier that an individual, organization, or device creates, owns, and controls. Unlike traditional identifiers (like an email address or government ID), a DID is not issued by a central authority. Instead, it is anchored to a verifiable data registry, most commonly a public blockchain like Ethereum, Polygon, or Sovrin. This architecture ensures that no single entity can unilaterally revoke or censor your identity, returning control to the user.

Each DID resolves to a DID Document (DID Doc), a JSON-LD file that contains the cryptographic material and service endpoints necessary for interactions. The DID Doc typically includes public keys for authentication and signing, along with pointers to services like Verifiable Credential issuance or encrypted communication channels. The resolution process—turning a DID string into its corresponding DID Doc—is standardized by the W3C, allowing for interoperability across different networks and systems.

Creating a DID is a cryptographic operation, not a transactional one. For a did:ethr method on Ethereum, you generate an Ethereum key pair. The DID is derived from the public key (e.g., did:ethr:0x5B38Da6a701c568545dCfcB03FcB875f56beddC4). The corresponding private key signs updates to the DID Doc, which are recorded on-chain. Other popular methods include did:key for simple, offline identifiers and did:web for identifiers resolvable via HTTPS, each with different trade-offs in decentralization and complexity.

Managing a DID involves updating its DID Document to rotate keys, add new service endpoints, or delegate authority. For blockchain-anchored DIDs, this requires submitting a signed transaction. It's critical to implement secure key management practices from the start. Using a hardware wallet for the root key and deriving session keys for daily use is a recommended pattern. Lost keys on a blockchain-based DID can render the identifier permanently unusable, as there is no central recovery service.

The primary use case for DIDs is to serve as the subject identifier for Verifiable Credentials (VCs). When you receive a VC (like a digital driver's license), it is cryptographically bound to your DID. To present proof, you generate a Verifiable Presentation signed with your DID's private key, allowing the verifier to check the credential's validity and your control over the DID without contacting the issuer. This creates a trust model based on cryptographic proof rather than API calls to centralized databases.

When setting up your framework, choose a DID method that aligns with your requirements for decentralization, transaction cost, and ecosystem support. For broad Ethereum Virtual Machine (EVM) compatibility, did:ethr is robust. For testing or non-blockchain applications, did:key or did:web are simpler. Libraries like Spruce ID's didkit, Microsoft's ION SDK for Bitcoin, or Veramo provide multi-method support, abstracting the underlying complexity and letting you focus on building your identity application.

Credential issuance is the process where a trusted entity, known as the issuer, creates a digitally signed attestation about a subject (the holder). The core technical standard for this is the W3C Verifiable Credentials Data Model. A credential is a JSON-LD document containing claims (e.g., "degreeType": "Bachelor of Science"), metadata (issuer DID, issuance date), and a cryptographic proof, typically a digital signature. This proof binds the data to the issuer's Decentralized Identifier (DID), making the credential tamper-evident and verifiable by any third party.

To issue a credential, you must first establish your issuer identity on a supported blockchain or DID method. For example, using the did:ethr method on Ethereum, you would create a DID document controlled by a private key. A common library for this is Veramo. The issuance flow involves: 1) The holder presents a DID and a verifiable presentation request; 2) The issuer's backend constructs the credential JSON; 3) The issuer signs the credential using their private key (e.g., with ES256K or EdDSA); 4) The signed credential is delivered to the holder, often as a JWT or a JSON-LD Proof.

Here is a simplified code example using Veramo's createVerifiableCredential method:

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const credential = await agent.createVerifiableCredential({
  credential: {
    issuer: { id: 'did:ethr:0x123...' },
    credentialSubject: {
      id: 'did:ethr:0x456...', // Holder's DID
      alumniOf: 'Example University',
      degree: 'Computer Science'
    }
  },
  proofFormat: 'jwt',
  save: false
});

This generates a signed JWT string containing the credential. The holder can store this in their digital wallet.

Critical design considerations include selecting appropriate credential schemas for interoperability. Public schemas can be registered on platforms like the Schema.org-aligned vc.revocation registry or custom JSON schemas. You must also plan for credential status (revocation). Options include maintaining a revocation list (e.g., a StatusList2021) or using smart contracts for on-chain status checks. The choice impacts verification complexity and user privacy.

Finally, the issuer must expose a well-known endpoint or API for credential verification. This provides the public keys associated with the issuer's DID, allowing verifiers to cryptographically check the signature's validity. The entire system's trust is rooted in this verifiable link between the issuer's public DID and the signed credential, enabling portable, user-controlled credentials that can be presented across different platforms without relying on the original issuer's live API.

The core principle of self-sovereign identity (SSI) is user-centric data control. Therefore, the storage of Verifiable Credentials (VCs) must not rely on a central database controlled by the issuer or a third party. Instead, credentials are stored in a digital wallet under the user's sole control. This wallet can be a mobile app, a browser extension, or a hardware device. The storage system must protect against data loss (via secure backups) and unauthorized access (via strong encryption and biometric locks).

For technical implementation, the W3C Verifiable Credentials Data Model is the standard. A VC is a JSON-LD document containing claims (the actual data), metadata (issuer, issuance date), and a cryptographic proof (like a digital signature). The wallet stores these signed JSON objects. When presenting a credential, the user's wallet does not send the raw VC. Instead, it creates a Verifiable Presentation, which is a new signed package that can contain selective disclosures, revealing only the necessary attributes to the verifier.

A critical design choice is between local-only storage and cloud-synced storage. Local storage (on-device) offers maximum privacy but risks permanent loss if the device is damaged. Cloud-synced storage, using encrypted personal data vaults (like those specified by the Solid Protocol), provides backup and cross-device access. Here, the user's private keys never leave their device; only the encrypted ciphertext is synced. The Decentralized Identifiers (DIDs) and DIDComm protocols are used to establish secure, encrypted communication channels for transmitting presentations between wallets.

Developers can use SDKs from SSI platforms to implement this. For example, using Trinsic's ecosystem, you would use their SDK to create a wallet, store credentials, and generate presentations. A simplified code snippet for storing a credential might look like:

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// After receiving a credential offer from an issuer
const credential = await wallet.getCredentialOffer(offerId);
await wallet.insertCredential(credential);
console.log('Credential stored locally with ID:', credential.id);

The SDK handles the underlying encryption and storage details, allowing you to focus on the user experience.

Security considerations are paramount. The wallet must implement key derivation from a user-owned seed phrase (BIP-39) to generate deterministic keys for signing. Credentials should be encrypted at rest using algorithms like AES-256-GCM. For high-value credentials, integration with hardware security modules (HSMs) or secure enclaves provides an extra layer of protection for private key operations, ensuring keys are never exposed in application memory.

Finally, the design must account for credential lifecycle management. Users need to be able to easily view, organize, revoke consent for presentations, and delete credentials. The architecture should also support credential renewal and status checks (e.g., querying a revocation registry) without compromising privacy. By decentralizing storage and placing cryptographic control in the user's hands, this design fulfills the core promise of SSI: true ownership of digital identity.

A Verifiable Presentation (VP) is a wrapper that contains one or more Verifiable Credentials (VCs) and is cryptographically signed by the holder. Its primary function is to enable selective disclosure. The holder, not the issuer, controls what information from their credentials is shared. The presentation protocol defines the data model and proof mechanism for this operation. Common standards include the W3C's Verifiable Presentations Data Model and the JWT-based presentation format used by many decentralized identity wallets.

Building a presentation involves several key components. First, you need the presentation object itself, which includes metadata like its unique id, type (e.g., VerifiablePresentation), the holder (the presenter's DID), and the verifiableCredential array. Crucially, you must generate a proof. For a JWT presentation, this is a signed JWT where the payload is the presentation object. For a Linked Data Proof, you would create a proof object with a type like Ed25519Signature2020 and a verificationMethod pointing to the holder's public key.

Here is a simplified example of a JWT Verifiable Presentation payload before signing:

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{
  "vp": {
    "@context": ["https://www.w3.org/2018/credentials/v1"],
    "type": ["VerifiablePresentation"],
    "verifiableCredential": ["eyJ0eXAiOiJKV1QiLCJhbGciOiJFUzI1Nk..."],
    "holder": "did:key:z6MkhaXgBZDvotDkL5257faiztiGiC2QtKLGpbnnEGta2doK"
  },
  "iss": "did:key:z6MkhaXgBZDvotDkL5257faiztiGiC2QtKLGpbnnEGta2doK",
  "nbf": 1685633524,
  "jti": "urn:uuid:3978344f-8596-4c3a-a978-8fcaba3903c5"
}

The verifiableCredential field contains the signed JWT string of the credential(s) being presented. The entire structure is then signed by the holder to produce the final VP JWT.

For advanced use cases, you can implement Selective Disclosure methods. With JWT, this often means using SD-JWT (Selective Disclosure JWT) or similar schemes where disclosed claims are hashed. With JSON-LD and BBS+ signatures, you can create derived proofs that allow the holder to cryptographically prove only specific attributes from a credential without revealing the entire document. This is a core privacy-enhancing feature of SSI.

The verifier's role is to: 1) Verify the presentation's signature using the holder's DID document, 2) Verify the signature and status of each embedded credential using the issuer's DID, and 3) Validate that the disclosed claims satisfy their policy. This completes the trust triangle, establishing that the claims are authentic (from a known issuer), tamper-proof, and presented by the rightful holder.

When implementing, consider interoperability. Use established libraries like did-jwt-vc (JavaScript), ssi-sdk (Go), or aries-cloudagent-python. Test your presentations against the W3C VC Test Suite and ensure your holder's wallet can correctly generate the proof type you require. The presentation is the user-facing culmination of the SSI flow, so its security and usability are paramount.

A Self-Sovereign Identity (SSI) framework allows individuals to own and control their digital identity without relying on centralized authorities. At its core, SSI is built on three key components: Decentralized Identifiers (DIDs), Verifiable Credentials (VCs), and Verifiable Presentations (VPs). A DID is a unique, cryptographically verifiable identifier (e.g., did:ethr:0x123...) stored on a blockchain or other decentralized network. VCs are digital, tamper-evident credentials issued by trusted entities, while VPs are the data packages a user shares to prove specific claims. This architecture shifts control from centralized databases to the individual's wallet.

The foundation of any SSI system is secure key management. A user's DID is associated with a public/private key pair. The private key, which must be kept secret, is used to sign credentials and presentations, proving ownership. For Ethereum-based DIDs using the did:ethr method, keys are typically managed by a standard Ethereum wallet like MetaMask. The critical challenge is ensuring this private key is both secure and recoverable. Simple device storage is insufficient for a long-term identity; robust strategies like social recovery, multi-signature wallets, or hardware security modules (HSMs) are essential to prevent permanent loss.

Implementing a basic SSI flow involves several steps. First, a user generates a DID, often derived from their blockchain wallet address. Using the DIDKit library by SpruceID or Veramo framework, a developer can create and resolve DIDs programmatically. For example, creating a did:ethr DID in Veramo involves specifying the Ethereum provider and network. The user then requests a Verifiable Credential, like a proof of age, from an issuer. The issuer signs the credential with their own DID, and the user stores it in their digital wallet. The credential's cryptographic proof is verified against the issuer's DID on the blockchain.

When a service requests proof (e.g., "Are you over 18?"), the user creates a Verifiable Presentation. This presentation contains only the necessary credential data and is signed with the user's private key. The verifier can check the signatures on both the presentation and the embedded credential without contacting the original issuer, enabling privacy-preserving verification. Standards from the World Wide Web Consortium (W3C) ensure interoperability between different SSI systems. Code examples for these interactions are available in the Veramo documentation and SpruceID tutorials.

For recovery, social recovery guardians or multi-signature schemes are the most user-friendly solutions. In a social recovery setup, a user designifies trusted individuals or devices as guardians. If the primary key is lost, a majority of guardians can authorize a reset to a new key. Protocols like Ethereum's ERC-4337 (Account Abstraction) enable smart contract wallets with built-in social recovery logic. Alternatively, using a hardware wallet as a secure element for key generation and signing significantly reduces the risk of compromise, though it requires a physical backup seed phrase stored offline.

Developers building SSI applications must prioritize privacy by design. Use zero-knowledge proofs (ZKPs) via circuits (e.g., with Circom) to allow users to prove statements like "I am over 18" without revealing their birth date. Be mindful of DID method selection—did:ethr for Ethereum ecosystems, did:key for simple scenarios, or did:web for web-based identities. The ultimate goal is to create systems where users have portable, private, and persistent control over their identity data, moving beyond the vulnerabilities of centralized logins and certificate authorities.

A self-sovereign identity (SSI) framework allows users to control their digital identifiers and verifiable credentials without relying on centralized authorities. To be effective, an SSI system must achieve interoperability—the ability for different systems and vendors to exchange and verify credentials seamlessly. This requires strict adherence to open standards, primarily the W3C Verifiable Credentials Data Model v2.0 and the Decentralized Identifiers (DIDs) v1.0 specification. Conformance testing ensures your implementation correctly follows these standards, preventing vendor lock-in and enabling global usability.

The foundation of technical interoperability is the DID document. This JSON-LD document describes the cryptographic keys, services, and protocols associated with a DID. When setting up your framework, you must correctly resolve DIDs to their documents. For example, a did:key identifier resolves locally, while did:ethr or did:web require network calls. Your DID resolver must handle multiple methods. Conformance testing involves verifying that your resolver correctly parses the publicKeyJwk, verificationMethod, and service endpoints as defined in the DID Core specification.

For credential issuance and verification, you must implement the W3C Verifiable Credentials (VC) data model. A VC is a JSON object with specific mandatory fields: @context, id, type, issuer, issuanceDate, credentialSubject, and proof. The proof contains the cryptographic signature, typically using EdDSA with Ed25519 or ES256K. Conformance testing validates the structure, signature scheme, and data integrity of your VCs. Tools like the W3C VC Test Suite can automate this validation against the official test vectors.

Presentation Exchange is a critical protocol for interoperability, defined by the Decentralized Identity Foundation (DIF). It standardizes how a verifier (relying party) requests credentials from a holder (user). The request is a Presentation Definition, a JSON object specifying the required credential types, constraints, and fields. The holder responds with a Presentation Submission. Testing this flow ensures your wallet can understand requests from any compliant verifier and that your verifier can process submissions from any compliant wallet, enabling cross-ecosystem trust.

To operationalize conformance testing, integrate continuous testing into your development pipeline. Use the DIF Conformance Test Suite for Interoperability or the Sphereon SSI-SDK test suites. These suites provide a battery of tests for DID resolution, VC issuance, and presentation exchange. For example, you can run a test to confirm your agent correctly handles a credential status check via a StatusList2021 entry. Automated testing catches deviations from the spec early, ensuring your framework remains compatible as standards evolve.

Finally, consider governance frameworks and trust registries. Interoperability isn't just technical; it's also about agreed-upon business rules and accredited issuers. The Trust over IP (ToIP) model provides a layered architecture for this. Implement a verifiable data registry (like a blockchain) for DIDs and use a governance framework to define which issuers are trusted for specific credential types. Conformance testing at this level involves auditing your system against the rules in the chosen governance framework, completing the end-to-end setup of a production-ready SSI framework.

To solidify your understanding, integrate the SSI framework into a practical use case. A common starting point is building a decentralized application (dApp) for credential verification. For example, create a simple web app that allows users to present a VerifiableCredential proving they are over 18. Your backend, using the did:key resolver and verification library, would check the credential's cryptographic proof and the issuer's DID status on the ledger. This moves the theory into a working prototype that demonstrates user-controlled data flow.

For production systems, consider these critical next steps: Upgrade to a public DID method like did:ion or did:ethr for persistent, resolvable identities on a blockchain. Implement selective disclosure using technologies like BBS+ signatures to reveal only specific credential attributes. Explore revocation registries such as the W3C Status List 2021 to manage credential status without compromising privacy. Audit your code and key management practices, as the security of the user's privateKey is paramount in SSI systems.

The ecosystem offers powerful tools for advanced implementations. Explore AnonCreds for advanced zero-knowledge proof capabilities or OID4VP (OpenID for Verifiable Presentations) for standardized authentication flows. Frameworks like Trinsic, Veramo, and Serto provide SDKs that abstract much of the complexity. Continue your learning through the W3C Verifiable Credentials Data Model specification and the Decentralized Identity Foundation's working groups. By building on these standards and tools, you contribute to a more interoperable and user-centric digital identity layer for the web.