What an anchor is
An anchor is a small transaction written to the Concordium blockchain that records a cryptographic hash of a verification record — not the record itself. A hash is a one-way fingerprint: the same input always produces the same hash, but the hash cannot be reversed to recover the input. So the anchor proves that a specific record existed at a specific time without putting any of its contents — and certainly nothing about the visitor — on-chain.No personal data is ever written to the blockchain. The anchor is a hash; the date of birth, name, and identity that the zero-knowledge proof is built on are never transmitted to Veriox in the first place (see Zero-Knowledge Proofs).
The two anchors
Each verification produces up to two anchors:| Anchor | Code | When | Records |
|---|---|---|---|
| Request anchor | CCDVRA | When the verification challenge is created | The exact request shown to the visitor — the age threshold, accepted identity issuers, and a one-time nonce |
| Audit anchor | CCDVAA | When a proof passes | The full audit record — the request, the submitted proof, and the result, bound together |
Why this matters
Immutability
Once a transaction is finalised on the Concordium blockchain, it cannot be altered, backdated, or deleted — not by Veriox, not by anyone. The blockchain is maintained by an independent, decentralised network of validators, so there is no single party who can quietly rewrite history. A row in a database says “trust us, this is what happened.” An anchored record is different: because the on-chain hash is fixed the moment it is written, any later change to the stored record would no longer match the anchor. The audit trail becomes tamper-evident — alterations are detectable rather than invisible.Independence
The anchor lives on a public blockchain, not inside Veriox’s systems. That means the evidence does not depend on Veriox continuing to exist, on our database being intact, or on our word. Anyone with the stored record can confirm it against the chain themselves.Compliance
If a regulator or auditor asks you to prove that a particular visitor completed age verification, you have cryptographic evidence that the verification happened, what was checked, and when — independently of Veriox. This is the difference between an audit trail you have to vouch for and one that vouches for itself.Verifying a record yourself
Every passed verification in your dashboard can be checked against the chain. On the Audit record tab of a verification, the Verify against chain button:Recomputes the hash in your browser
Your browser takes the stored audit record and recomputes its hash locally, using the Concordium SDK.
Fetches the anchor from the blockchain
It reads the anchored value directly from a public Concordium node — not from Veriox.