Offline Verification Walkthrough

This guide walks through verifying an Attestix-issued Verifiable Credential with no internet connection. All that is required is the public key of the issuer, which is embedded in the DID.

Scenario

You are a regulator. A supplier has sent you a Declaration of Conformity VC for their high-risk AI system. You want to confirm:

1. The VC was signed by the claimed issuer.
2. The signature has not been tampered with.
3. The audit trail behind it is internally consistent.

No network calls. Everything should verify from the JSON blob and the public key.

Prerequisites

pip install attestix

Step 1 / Fetch the artefacts

Ask the supplier to send:

• The Verifiable Credential JSON (Annex V Declaration of Conformity)
• The issuer's DID document (or the embedded public key)
• Optionally, the hash-chained audit trail export

All three come from export_compliance_pack:

from attestix.services.compliance_service import ComplianceService

pack = ComplianceService().export_compliance_pack(
    agent_id="attestix:f9bdb7a94ccb40f1"
)
# pack -> zip with credential.json, did-document.json, audit.ndjson

Step 2 / Verify the signature

import json
from attestix.services.credential_service import CredentialService

credential_svc = CredentialService()

with open("credential.json") as f:
    vc = json.load(f)

ok = credential_svc.verify_credential_offline(
    credential=vc,
    did_document_path="did-document.json",
)
# -> True (or False with a reason)

Internally this:

1. Canonicalises the VC with RFC 8785 JCS.
2. Extracts the proofValue field.
3. Looks up the verificationMethod key in the DID document.
4. Verifies the Ed25519 signature per RFC 8032.

If the signature is valid, you have cryptographic proof that the issuer controlled the private key at signing time.

Step 3 / Verify the audit chain

from attestix.services.provenance_service import ProvenanceService

ok, first_bad_index = ProvenanceService().verify_audit_chain(
    trail_path="audit.ndjson"
)
# -> (True, None) or (False, 42)

Each entry is checked with SHA-256(prev_hash + canonical_json(entry_without_hash_fields)) = hash, where canonical_json uses sorted keys and compact separators. Any tamper with any row invalidates all subsequent rows.

Step 4 / Verify the declaration against the profile

ok = ComplianceService().verify_declaration_offline(
    declaration_path="credential.json",
    profile_path="profile.json",
)

Confirms the declaration references the correct risk category, notified body, and covered articles.

Full example script

A runnable script is included in the repo at examples/offline_verify.py:

python examples/offline_verify.py ./compliance-pack.zip

Output:

[ok] signature verified (Ed25519Signature2020)
[ok] audit chain consistent (1,247 entries)
[ok] declaration references profile:3c8f21e9
[ok] 9 / 9 obligations met (Articles 9, 10, 11, 12, 13, 14, 15, 43, Annex V)
VERIFY = PASS

Why this matters

Every other compliance artefact you receive as a regulator comes as a PDF or a dashboard screenshot. Neither is cryptographically bindable to a specific operator or point in time. Attestix artefacts are.

The same function is what a peer agent calls when it decides whether to trust another agent's capability claim. See UCAN delegation for how delegation chains are verified the same way.