Setting Up a Verifiable Credential System for Learning Engagement

A Verifiable Credential (VC) system provides a standardized, cryptographically secure way to represent digital claims, such as course completions or skill badges, in a machine-verifiable format. Unlike traditional certificates, VCs are owned by the learner, stored in a digital wallet, and can be shared selectively without relying on a central issuing authority for verification. This guide explains how to implement such a system using open standards like the W3C Verifiable Credentials Data Model and decentralized identifiers (DIDs).

The core architecture involves three primary roles: the Issuer (e.g., an educational platform), the Holder (the learner), and the Verifier (e.g., an employer or another platform). The issuer signs a credential with their private key, the holder stores it securely, and any verifier can cryptographically check the credential's authenticity and integrity without contacting the issuer directly. This creates a trust model based on cryptography rather than centralized databases.

For developers, building this requires selecting a signature suite (like Ed25519Signature2020 or JSON Web Signatures), a method for resolving issuer DIDs, and a protocol for credential presentation. We'll use practical examples with libraries such as did-jwt-vc or vc-js to demonstrate issuing a credential in JSON-LD format, which structures data for both humans and machines.

A key advantage for learning engagement is the ability to create portable and interoperable achievement records. A learner can aggregate credentials from multiple sources—online courses, workshop participation, project contributions—into a single, verifiable Learning Passport. This enables new models for recognition, such as unlocking advanced course content or qualifying for token-gated communities based on proven skills.

This guide provides the technical foundation. Subsequent sections will detail the steps: setting up an issuer backend, creating a holder wallet application, and building a verifier service. We'll implement a complete flow for a credential like "Completed Advanced Solidity Course" using the Ethereum blockchain for DID resolution and credential status checks to ensure the credential has not been revoked.

A verifiable credential (VC) system for learning engagement allows you to issue tamper-proof, learner-owned digital records of achievements, skills, or completions. This guide focuses on implementing a system using the W3C Verifiable Credentials Data Model and Decentralized Identifiers (DIDs). You should be familiar with core Web3 concepts like public-key cryptography, digital signatures, and the difference between on-chain and off-chain data storage. For a practical implementation, we'll reference the did:key method and the Ed25519 signature suite, as they are widely supported and don't require a blockchain for issuance.

You will need a development environment with Node.js (v18 or later) and a package manager like npm or yarn installed. We'll use the @digitalbazaar/ed25519-verification-key-2020 and @digitalbazaar/ed25519-signature-2020 libraries for cryptographic operations, and @digitalbazaar/vc for handling the credential lifecycle. Start by initializing a new project and installing these dependencies: npm install @digitalbazaar/ed25519-verification-key-2020 @digitalbazaar/ed25519-signature-2020 @digitalbazaar/vc. Ensure you have a basic understanding of JSON-LD contexts, as they define the vocabulary for your credentials.

The core entities in this system are the Issuer (the learning platform), the Holder (the learner), and the Verifier (an employer or another platform). The Issuer creates a DID and corresponding key pair to sign credentials. The Holder receives and stores the credential in a digital wallet. The Verifier can cryptographically check the credential's authenticity and issuer without contacting the original platform. This guide will walk you through generating a DID document, creating a credential schema, issuing a signed credential, and performing a verification check using sample code.

W3C Verifiable Credentials (VCs) are a standard for creating tamper-evident digital credentials that can be cryptographically verified. In a learning context, they allow institutions to issue credentials—like course certificates, skill badges, or degree attestations—as JSON-LD documents signed with a private key. The learner holds these credentials in their digital wallet, a secure software application, and can present them to any verifier, such as a potential employer or another educational platform, without needing to contact the original issuer. This model shifts control from centralized databases to the individual, enabling self-sovereign identity for education.

The foundation of a VC system is the Decentralized Identifier (DID), a new type of globally unique identifier. Unlike an email address controlled by a provider, a DID is controlled by its subject (the learner) and resolves to a DID Document containing public keys and service endpoints. For example, a learner's DID might be did:key:z6MkhaXgBZDvotDkL5257faiztiGiC2QtKLGpbnnEGta2doK. This document, often stored on a blockchain or other decentralized network, allows any party to fetch the public keys needed to verify a credential's signature without relying on a central authority.

To set up a basic system, you need three roles: an issuer (the learning platform), a holder (the learner), and a verifier (an employer). The issuer creates a VC by signing a JSON structure containing claims (e.g., "achievement": "Advanced Solidity") with their private key and embedding the learner's DID as the credential subject. The holder stores this signed VC in their wallet. When applying for a job, the holder creates a Verifiable Presentation—a wrapper that may contain one or more VCs—and selectively discloses it to the verifier, who uses the issuer's public DID to cryptographically verify the signatures and authenticity.

For developers, implementing issuance involves using libraries like did-jwt-vc (JavaScript) or vc-js. A minimal issuance snippet in JavaScript might look like this:

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const vc = await createVerifiableCredential({
  issuer: 'did:ethr:0x123...',
  subject: 'did:key:z6Mk...',
  claims: { 'courseCompleted': 'Blockchain Fundamentals' },
  signer: issuerSignerFunction
});

The resulting VC is a portable JSON file the learner can export or share via a QR code. The verifier's system would use a similar library's verifyCredential() function, fetching the issuer's public key from their DID Document on the blockchain to check the signature.

Key considerations for a production system include revocation methods like status lists or smart contracts, choosing a DID method (e.g., did:ethr for Ethereum, did:web for HTTPS), and ensuring privacy through techniques like zero-knowledge proofs for selective disclosure. For learning engagement, this architecture enables interoperable skill passports, allowing learners to build a verifiable, lifelong record of achievements across different platforms, moving beyond locked-in institutional transcripts.

The issuer backend is the core component that creates, signs, and manages the lifecycle of Verifiable Credentials. For this tutorial, we'll build a simple Express.js server using the did-jwt-vc and ethr-did libraries to create Ethereum-based Decentralized Identifiers (DIDs) and sign JWTs as VCs. Start by initializing a new Node.js project and installing the required dependencies: npm init -y followed by npm install express did-jwt-vc ethr-did ethers@5 cors.

The server needs a secure identity to sign credentials. We'll use ethr-did to create an issuer DID from an Ethereum private key. Store this key securely using environment variables (e.g., in a .env file). The DID document, anchored to the Ethereum blockchain, provides the public key needed for verification. Initialize the issuer in your index.js: const issuer = new EthrDID({ identifier: '0xYourAddress', privateKey: process.env.ISSUER_PRIVATE_KEY, chainNameOrId: 'sepolia' }).

Define the VC schema for learning engagement. A Verifiable Credential is a JSON object containing claims, metadata, and a proof. A basic schema for a "Course Completion" credential includes the learner's DID, the course ID, a completion timestamp, and a score. The structure must comply with the W3C Verifiable Credentials Data Model. Use createVerifiableCredentialJwt from did-jwt-vc to package this data into a signed JWT, which becomes the portable, tamper-evident credential.

Create an Express endpoint, POST /api/issue-credential, that accepts a learner's DID and course details. The endpoint logic will: 1) validate the request, 2) construct the VC payload with a unique ID and issuance date, 3) sign it using the issuer's DID, and 4) return the JWT VC to the learner. Implement proper error handling and input validation. For production, add rate limiting and authentication to this endpoint.

To enable verification, expose a second endpoint, GET /api/.well-known/did.json, that serves the issuer's DID document. This public document, resolvable via the DID, contains the public key necessary for any verifier (like a blockchain smart contract or another service) to cryptographically verify the signatures on your issued credentials without interacting with your backend directly.

Finally, test the complete flow. Run the server with node index.js. Use a tool like curl or Postman to request a credential for a test learner DID, then verify the returned JWT using a library like did-jwt-vc's verifyCredential function. The next step will involve creating a smart contract verifier that can check these credentials on-chain.

A credential schema is the formal blueprint for your verifiable credentials. It defines the data model, specifying the properties (like courseId, completionDate, finalGrade), their data types (string, integer, dateTime), and whether they are required or optional. This standardization is critical for interoperability, ensuring that any verifier (like an employer's system) can understand and process the credential's contents without prior negotiation with the issuer. Schemas are typically published to a decentralized registry, such as a blockchain or an IPFS (InterPlanetary File System) hash, creating a permanent, tamper-evident reference.

For learning credentials, your schema must balance detail with privacy. Essential properties often include: issuer (your institution's DID), recipient (the learner's DID), achievement (e.g., "Advanced Solidity Developer"), issuedDate, and credentialSubject.id. You can extend this with learning-specific fields like courseModule, skillsDemonstrated (an array), or assessmentScore. Avoid including Personally Identifiable Information (PII) like full names or emails directly in the schema data; instead, link to it via the decentralized identifier (DID). This approach separates the credential's claim from the holder's private data.

Here is a simplified example of a JSON schema definition for a course completion credential, using the JsonSchemaValidator format common in the W3C Verifiable Credentials ecosystem:

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{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "credentialSubject": {
      "type": "object",
      "properties": {
        "id": { "type": "string", "format": "uri" },
        "achievement": { "type": "string" },
        "completionDate": { "type": "string", "format": "date-time" },
        "skillBadges": { "type": "array", "items": { "type": "string" } }
      },
      "required": ["id", "achievement", "completionDate"]
    }
  }
}

This schema ensures every issued credential contains a subject ID, an achievement title, and a completion timestamp, with an optional array for specific skills.

After defining your schema, you must publish it to a persistent, verifiable location. The most common method is to upload the schema JSON file to IPFS, which returns a Content Identifier (CID). This CID becomes the schema's unique, immutable address (e.g., ipfs://QmXample...). You then anchor this reference—often just the CID—on a blockchain like Ethereum or Polygon by recording it in a smart contract registry, such as those provided by the Veramo framework or Ethereum Attestation Service (EAS). This creates a public, timestamped proof of the schema's existence at a point in time, which issuers reference when creating credentials.

Designing for future-proofing is essential. Consider using versioning in your schema ID (e.g., your-schema-v1.0) to allow for non-breaking updates. Also, leverage selective disclosure capabilities from the start. This means structuring data so a learner can cryptographically prove a specific claim ("scored above 90%") from the credential without revealing all other data (like other grades or the exact date). Technologies like BBS+ signatures (used in AnonCreds) or zero-knowledge proofs (ZKPs) enable this, but the schema must support the necessary predicate logic.

Finally, document your schema publicly. Provide a human-readable description of each field, its purpose, and possible values. This documentation, alongside the on-chain reference, completes the design phase. It transforms your credential from a simple data packet into a robust, interoperable, and privacy-preserving asset that can be understood and trusted across the Web3 ecosystem, forming the foundation for the next step: configuring the issuance logic.

The core of a user-centric credential system is the wallet integration. Users need a secure, self-sovereign place to store their credentials, which is where blockchain wallets come in. For this guide, we'll use MetaMask as the example wallet, but the principles apply to any wallet supporting the Ethereum Provider API (window.ethereum). The first task is to detect the wallet in the user's browser and request a connection to your dApp. This establishes a secure communication channel and retrieves the user's public address, which acts as their primary decentralized identifier (DID).

Once connected, you can initiate the credential issuance process. The typical flow involves your backend server (from Step 2) signing a structured data payload. This payload, or Verifiable Credential (VC), contains the credential's metadata (like issuer, issuanceDate, credentialSubject.id). You then present this signed data to the user's wallet via a transaction-like request. For Ethereum, this is often done using the eth_signTypedData_v4 method, which prompts the user to sign the credential data, thereby cryptographically binding it to their wallet address and creating a Verifiable Presentation.

After the user signs, the credential is stored locally in their wallet. To enable users to share it, you must also implement a verification interface. This is a page or component where a verifier (e.g., another dApp or platform) can request to see a credential. Your dApp should listen for verification requests, often via WalletConnect or deep links, retrieve the signed credential from the user's wallet (requiring another user signature for consent), and validate its cryptographic proofs against the issuer's public key on-chain or in a registry.

For a concrete code example, here is a simplified connection and signing flow using ethers.js:

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// 1. Connect to MetaMask
const provider = new ethers.BrowserProvider(window.ethereum);
const signer = await provider.getSigner();
const userAddress = await signer.getAddress();

// 2. Prepare credential data for signing (EIP-712 typed data)
const domain = { name: "LearningCredential", version: "1", chainId: 1 };
const types = { Credential: [{ name: "learner", type: "address" }, { name: "courseId", type: "string" }] };
const value = { learner: userAddress, courseId: "web3-101" };

// 3. Request user's signature
const signature = await signer.signTypedData(domain, types, value);
// Send `signature` and `value` to your backend for issuance.

Key considerations for production include gasless transactions for a smoother UX—using meta-transaction relayers or signature-based off-chain checks. You must also decide on the credential format; while the example uses a simple EIP-712 structure, you may adopt W3C Verifiable Credentials data model with JSON-LD, which requires more complex parsing. Furthermore, always provide clear user prompts explaining what they are signing and why, as signing opaque data is a major security concern for less experienced users.

Finally, remember that wallet integration is not a one-time event. You should manage connection state persistence, handle network changes, and listen for account switches (accountsChanged event). A robust implementation allows users to seamlessly view their earned credentials within your dApp, share them with other applications, and build a portable, user-owned learning transcript that is not locked into any single platform.

The verification service is the backend component that processes credential issuance and verification requests. It acts as a secure intermediary between your application's frontend and the blockchain network. Its primary responsibilities are to: - Sign credentials with the issuer's private key. - Submit transactions to the credential registry smart contract. - Query the blockchain to verify credential status and validity. You can build this service using a Node.js/Express server, a Python Flask API, or any backend framework that can interact with an Ethereum client.

To interact with the blockchain, the service needs a connection to an RPC node. For development, you can use a service like Alchemy or Infura, or run a local node. The service also requires access to the issuer's wallet private key (securely stored in environment variables) to sign transactions. You will need the ABI (Application Binary Interface) and address of your deployed CredentialRegistry contract. Here's a basic setup in Node.js using Ethers.js:

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const { ethers } = require('ethers');
const provider = new ethers.providers.JsonRpcProvider(process.env.RPC_URL);
const wallet = new ethers.Wallet(process.env.ISSUER_PRIVATE_KEY, provider);
const contractABI = [...]; // Your contract ABI
const contractAddress = '0x...';
const contract = new ethers.Contract(contractAddress, contractABI, wallet);

The key function is issuing a credential. The service receives a credential payload (learner address, credential metadata URI) from the frontend, constructs the transaction, and sends it. The issueCredential function on the smart contract will mint an NFT/SBT to the learner's address. It's critical to implement proper error handling for failed transactions and gas estimation. After a successful transaction, the service should return the transaction hash to the frontend for user feedback and record-keeping.

For verification, the service provides a read-only endpoint. When a verifier (like an employer) needs to check a credential, they submit the credential's unique ID. The service then calls the getCredential view function on the smart contract, which returns the issuer address, issuance timestamp, and metadata URI. The service can fetch the actual JSON metadata from the URI (stored on IPFS or Arweave) and return a complete verification result, confirming the credential's authenticity and current validity status (e.g., not revoked).

Security is paramount. Never expose the issuer's private key in client-side code. All signing must occur server-side. Implement rate limiting on your API endpoints to prevent abuse. Use API keys or authentication (like JWT) to protect your issuance endpoint, ensuring only authorized systems (like your learning platform) can request credential minting. Log all issuance and verification events for audit purposes.

Finally, integrate this service with your frontend application. The learner's dashboard should call the issuance endpoint upon course completion. A "Verify Credential" feature for third parties should call the verification endpoint. By completing this step, you establish a trustless, automated system for issuing and verifying learning achievements, with the blockchain serving as the single source of truth.

You now have the foundational knowledge to implement a system where learners earn verifiable credentials (VCs) for completing courses or demonstrating skills. The architecture typically involves: an issuer (your learning platform) that signs credentials, a holder (the learner) who stores them in a digital wallet, and a verifier (an employer or another platform) that cryptographically checks their validity. This model, built on W3C Verifiable Credentials standards, creates portable, user-owned proof of achievement that is resistant to forgery.

To build a minimum viable product, start by defining your credential schema. Use a framework like Veramo or Trinsic to handle the cryptographic operations. For example, issuing a credential in Veramo involves creating a JSON-LD document with the learner's DID, the achievement data, and a proof type like Ed25519Signature2020. The credential is then packaged into a Verifiable Presentation when the user needs to share it. Ensure your issuer's DID is published on a decentralized ledger like Ethereum or Cheqd for public verification.

The next phase is integrating this issuance flow into your existing learning platform. Trigger credential minting via an API call upon course completion. Provide learners with a QR code containing a verifiable presentation request, which their wallet app can scan to receive the credential. For a seamless user experience, consider supporting popular wallet protocols like WalletConnect and credential formats such as W3C VC-JWT for broader compatibility across different verifiers.

Looking ahead, explore advanced features to increase utility. Implement revocation registries using smart contracts or the StatusList2021 specification to invalidate credentials if needed. Design conditional credentials that unlock only after passing an assessment. You can also create composite credentials that aggregate multiple micro-credentials into a certified skill portfolio. These features make your system more robust and valuable for learners.

Finally, test your system thoroughly before launch. Verify credentials using open-source tools like vc-js or the verifier SDK from your chosen framework. Audit the security of your private key management for issuance. Engage with the community through the DIF (Decentralized Identity Foundation) and W3C VC working group to stay updated on standards evolution. By implementing this, you move from centralized, siloed records to an interoperable ecosystem of trust for lifelong learning.