What is a Privacy Pass?
A Privacy Pass is the token your server exchanges for a claim result. It is what makes Relay able to return an answer without Persona learning who asked for it.
Privacy Pass is not something Persona invented. It is an open standard developed at the IETF, with published RFCs and public implementations, and it is used elsewhere on the internet for the same purpose: proving something is legitimate without revealing who is making the request.
Why a blind signature matters here
Issuing a pass and redeeming it are two separate moments. Issuance uses your API key, so Persona knows your platform asked for a pass. Redemption is meant to stand on its own, with nothing that ties it back to that earlier request.
A blind signature is what holds the two apart. Your side blinds the token before sending it to be signed, Persona signs it without seeing the underlying value, and your side unblinds the signature locally. The result is a valid token that cannot be traced back to the request that created it.
That is what “double-blind” means in practice for Relay. The separation is structural rather than a policy commitment, which is what lets both sides rely on it.
How your integration uses one
For most teams this is handled for you. The Persona server SDKs and the Relay Gateway Service perform the blinding, signing, and unblinding steps themselves, so a normal integration issues a pass and later redeems it without implementing any cryptography.
Both are kept current as the standard evolves, so you are not tracking changes to it yourself.
Two practical properties do reach your code:
- Issuance uses your API key. Redemption does not. Issuing a pass identifies your platform to Persona. Redeeming it uses the token instead, which is what keeps the two steps separate.
- A pass can only be redeemed once. After a successful redemption the token is spent, so your integration should treat retries carefully. The SDKs and the Gateway Service handle that for you.
A Privacy Pass is also the unit Relay is billed on, and it is billed when it is created rather than when it is redeemed. Issue passes when you expect to redeem them rather than well ahead of time.
See it in the flow
Persona hosts a public demo at explore.withpersona.com/relay. The activity panel shows each step as it happens, including the moment a pass is issued and the moment it is redeemed for a claim result. You can switch that panel to a technical view to see the same steps as SDK calls, gateway requests, or raw API requests, which is the clearest way to watch the two halves stay separate.
Full technical documentation
The developer documentation is the source of truth:
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