Decentralized Identity Based Secure Evidence Exchange for Automated Security Questionnaires

In the era of SaaS‑first procurement, security questionnaires have become the primary gatekeeper for every contract. Companies must repeatedly provide the same pieces of evidence—SOC 2 reports, ISO 27001 certificates, penetration‑test results—while ensuring that the data remains confidential, tamper‑evident, and auditable.

 
Enter Decentralized Identifiers (DIDs) and Verifiable Credentials (VCs).
These W3C standards enable cryptographic ownership of identities that exist outside any single authority. When combined with AI‑driven platforms like Procurize, DIDs turn the evidence exchange process into a trust‑anchored, automated workflow that scales across dozens of vendors and multiple regulatory frameworks.

Below we dive into:

1. Why traditional evidence exchange is fragile.
2. Core principles of DIDs and VCs.
3. A step‑by‑step architecture that plugs DID‑based exchange into Procurize.
4. Real‑world benefits measured from a pilot with three Fortune 500 SaaS providers.
5. Best practices and security considerations.

1. The Pain Points of Conventional Evidence Sharing

These challenges are amplified when questionnaires are real‑time: a vendor’s security team expects an answer within hours, yet the evidence must be fetched, reviewed, and securely transmitted.

2. Foundations: Decentralized Identifiers & Verifiable Credentials

2.1 What is a DID?

A DID is a globally unique identifier that resolves to a DID Document containing:

• Public keys for authentication and encryption.
• Service endpoints (e.g., a secure API for evidence exchange).
• Authentication methods (e.g., DID‑Auth, X.509 binding).

{
  "@context": "https://w3.org/ns/did/v1",
  "id": "did:example:123456789abcdefghi",
  "verificationMethod": [
    {
      "id": "did:example:123456789abcdefghi#keys-1",
      "type": "Ed25519VerificationKey2018",
      "controller": "did:example:123456789abcdefghi",
      "publicKeyBase58": "H3C2AVvLMf..."
    }
  ],
  "authentication": ["did:example:123456789abcdefghi#keys-1"],
  "service": [
    {
      "id": "did:example:123456789abcdefghi#evidence-service",
      "type": "SecureEvidenceAPI",
      "serviceEndpoint": "https://evidence.procurize.com/api/v1/"
    }
  ]
}

No central registry controls the identifier; the owning entity publishes and rotates the DID Document on a ledger (public blockchain, permissioned DLT, or a decentralized storage network).

2‑2 Verifiable Credentials (VCs)

VCs are tamper‑evident statements issued by a issuer about a subject. A VC can encapsulate:

• The hash of an evidence artifact (e.g., a SOC 2 report PDF).
• The validity period, scope, and applicable standards.
• Issuer‑signed attestations that the artifact meets a specific control set.

{
  "@context": [
    "https://w3.org/2018/credentials/v1",
    "https://example.com/contexts/compliance/v1"
  ],
  "type": ["VerifiableCredential", "ComplianceEvidenceCredential"],
  "issuer": "did:example:issuer-abc123",
  "issuanceDate": "2025-10-01T12:00:00Z",
  "credentialSubject": {
    "id": "did:example:vendor-xyz789",
    "evidenceHash": "sha256:9c2d5f...",
    "evidenceType": "SOC2-TypeII",
    "controlSet": ["CC6.1", "CC6.2", "CC12.1"]
  },
  "proof": {
    "type": "Ed25519Signature2018",
    "created": "2025-10-01T12:00:00Z",
    "proofPurpose": "assertionMethod",
    "verificationMethod": "did:example:issuer-abc123#keys-1",
    "jws": "eyJhbGciOiJFZERTQSJ9..."
  }
}

The holder (the vendor) stores the VC and presents it to a verifier (the questionnaire respondent) without revealing the underlying document, unless explicitly authorized.

3. Architecture: Plugging DID‑Based Exchange into Procurize

Below is a high‑level flowchart that illustrates how a DID‑enabled evidence exchange works with the Procurize AI questionnaire engine.

  flowchart TD
    A["Vendor Initiates Questionnaire Request"] --> B["Procurize AI Generates Answer Draft"]
    B --> C["AI Detects Required Evidence"]
    C --> D["Lookup VC in Vendor DID Vault"]
    D --> E["Verify VC Signature & Evidence Hash"]
    E --> F["If Valid, Pull Encrypted Evidence via DID Service Endpoint"]
    F --> G["Decrypt with Vendor‑Provided Session Key"]
    G --> H["Attach Evidence Reference to Answer"]
    H --> I["AI Refines Narrative with Evidence Context"]
    I --> J["Send Completed Answer to Requestor"]
    style A fill:#f9f,stroke:#333,stroke-width:2px
    style J fill:#9f9,stroke:#333,stroke-width:2px

3.1 Core Components

3.2 Integration Steps

1. Onboard Vendor DID – During vendor registration, generate a unique DID for the vendor and store its DID Document in the DID Vault.
2. Issue VCs – Compliance officers upload evidence (SOC 2 report) to the vault; the system computes a SHA‑256 hash, creates a VC, signs it with the issuer’s private key, and stores the VC alongside the encrypted artifact.
3. Configure Procurize – Add the vendor’s DID as a trusted source in the AI engine’s “evidence‑catalog” configuration.
4. Run a Questionnaire – When a security questionnaire asks for “SOC 2 Type II evidence,” Procurize AI:
   • Queries the vendor’s DID Vault for a matching VC.
   • Verifies the VC cryptographically.
   • Retrieves the encrypted evidence via the service endpoint.
   • Decrypts using an ephemeral session key exchanged through the DID‑auth flow.
5. Provide Auditable Proof – The final answer includes a reference to the VC (credential ID) and a hash of the evidence, enabling auditors to independently verify the claim without needing raw documents.

4. Pilot Results: Quantifiable Gains

A three‑month pilot was conducted with AcmeCloud, Nimbus SaaS, and OrbitTech—all heavy users of the Procurize platform. The following metrics were recorded:

Qualitative feedback highlighted the psychological trust boost: requestors felt confident because they could cryptographically verify that each piece of evidence originated from the claimed issuer and had not been tampered with.

5. Security & Privacy Hardening Checklist

1. Zero‑Knowledge Proofs for Sensitive Fields – Use ZK‑SNARKs when the VC needs to attest to a property (e.g., “the report is less than 10 MB”) without revealing the actual hash.
2. Revocation Lists – Publish DID‑based revocation registries; when an evidence artifact is superseded, the old VC is instantly invalidated.
3. Selective Disclosure – Leverage BBS+ signatures to reveal only the necessary credential attributes to the verifier.
4. Key Rotation Policies – Enforce a 90‑day rotation cycle for DID verification methods to limit key compromise impact.
5. GDPR consent records – Store consent receipts as VCs, tying the data subject’s DID to the specific evidence being shared.

6. Future Roadmap

The convergence of decentralized identity and generative AI will reshape how security questionnaires are answered, turning a historically bottleneck‑laden process into a frictionless trust transaction.

7. Getting Started: Quick‑Start Guide

# 1. Install the DID toolkit (Node.js example)
npm i -g @identity/did-cli

# 2. Generate a new DID for your organization
did-cli create did:example:my-company-001 --key-type Ed25519

# 3. Publish the DID Document to a resolver (e.g., Ceramic)
did-cli publish --resolver https://ceramic.network

# 4. Issue a VC for a SOC2 report
did-cli issue-vc \
  --issuer-did did:example:my-company-001 \
  --subject-did did:example:vendor-xyz789 \
  --evidence-hash $(sha256sum soc2-report.pdf | cut -d' ' -f1) \
  --type SOC2-TypeII \
  --output soc2-vc.json

# 5. Upload encrypted evidence and VC to the DID Vault (example API)
curl -X POST https://vault.procurize.com/api/v1/evidence \
  -H "Authorization: Bearer <API_TOKEN>" \
  -F "vc=@soc2-vc.json" \
  -F "file=@soc2-report.pdf.enc"

After these steps, configure Procurize AI to trust the new DID, and the next questionnaire asking for SOC 2 evidence will be answered automatically, backed by a verifiable credential.

8. Conclusion

Decentralized Identifiers and Verifiable Credentials bring cryptographic trust, privacy‑by‑design, and auditability to the once‑manual world of security questionnaire evidence exchange. When integrated with an AI‑driven platform like Procurize, they transform a multi‑day, high‑risk process into a matter of seconds while keeping compliance officers, auditors, and customers confident that the data they receive is authentic and immutable.

Adopting this architecture today positions your organization to future‑proof compliance workflows against tightening regulations, increasing vendor ecosystems, and the inevitable rise of AI‑enhanced security assessments.