Proof of integrity

One real VDA Witness record, published so you can check it yourself — with no account, no credentials, and no obligation to trust us or run our code.

The record

Rekor stores the SHA-256 of the head string, so the value inside the log entry is sha256("sha256:f72eb515a87560ec8254d3ff11a60ae06f169584a7c83306d660b1f7fe2bda68") — not the head itself. The command below shows how to check that yourself; it is the one step people most often mistake for a mismatch.

The full bundle — record, chain, anchor attestations, and a did.json snapshot — is at /proof/bundle.json.

1. Resolve it in Rekor — no VDA, no SDK

The strongest check is the one that does not involve us at all. This is a third-party log:

curl -s https://rekor.sigstore.dev/api/v1/log/entries/108e9186e8c5677acc7251e72424258ebf3c0553ae26a041804d156141b6b49ae49d2a5e398fc3a7 \
  | python -c 'import sys,json,base64,hashlib
d=json.load(sys.stdin); e=d[list(d)[0]]
inlog=json.loads(base64.b64decode(e["body"]))["spec"]["data"]["hash"]["value"]
head="sha256:f72eb515a87560ec8254d3ff11a60ae06f169584a7c83306d660b1f7fe2bda68"
print("logIndex :", e["logIndex"])
print("in log   :", inlog)
print("expected :", hashlib.sha256(head.encode()).hexdigest())
print("BINDS    :", inlog == hashlib.sha256(head.encode()).hexdigest())'

The entry is immutable, carries an inclusion proof, and is independently monitored. Its integratedTime is set by the log, not by us. We cannot alter, backdate, or withdraw it — which is the entire basis of the claim.

2. Verify the bundle offline

Zero network calls back to Witness. The verifier is Apache-2.0 and has no dependencies:

npm i vda-witness

curl -s https://witness.getvda.ai/proof/bundle.json > bundle.json
node -e '
  const b = require("./bundle.json");
  const { offlineVerify } = require("vda-witness/verify");
  offlineVerify(b).then(v => console.log(v.state));
'
# ANCHORED_VALID

Python: pip install "vda-witness[verify]".

3. Try to break it

A proof you cannot falsify is not a proof. Change one byte of any record body in bundle.json and re-run the verifier:

# flip a character anywhere inside records[0], then:
node -e '... offlineVerify(b) ...'
# BROKEN

Re-sign that tampered chain with a valid key and the internal checks pass again — but the head changes, and the head in Rekor does not. That is the whole argument, and you can run it.

What this does and does not prove

• Does: this exact record existed, in this exact chain position, no later than the Rekor entry's inclusion time — and has not changed since. VDA cannot rewrite it retroactively.
• Does not: say anything about whether the record's content is true. Witness seals asserted facts and makes them tamper-evident; it does not verify claims about the world. That boundary is documented, not hidden.
• Does not: extend to Sealed-tier records. The free self-serve tier is deliberately never anchored — those records are signed and chain-verifiable but carry no external commitment, so "provable even against VDA" does not apply to them. Anchoring is a paid-tier property and we would rather say so here than let the distinction blur.

Published from a dedicated account and chain that contains no customer data. Customer records are never public: every other proof endpoint on this service requires a key, and an unknown record id returns not-found rather than leaking existence.