Values are examples. Long hex is shortened with “…”.
Tip: press the left and right arrow keys to step.
Ser in one picture
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1 Alice enrolls
Alice looks at her iPhone. Face ID unlocks a key inside the phone. The phone sends Ser a signed request. Her face never leaves the phone.
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2 Ser checks and writes
Ser checks the request. If it passes, Ser adds a credential to its public book. A public number (the “nullifier”) names each credential.
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3 Bob’s app reads the book
Bob runs a chat app. His app looks up a number in the public book. Bob has no Apple device. He only reads.
The four characters
- Alice is a human. She owns the iPhone. She is the honest holder.
- Bob is a second human. He has no Apple device. He checks Alice, or he cheats.
- iPhone is Alice’s one Apple device. It has Face ID, a locked key and App Attest.
- Ser server is one box. It checks requests and keeps the public book.
Scenarios
Where it is today
- Works in tests The engine, the HTTP API, the SQLite store and the JavaScript SDK.
- Works on a desktop Zero-knowledge proofs, made and checked with ProveKit v1.0.3. This includes a draft proof for showing a credential to a peer.
- Not done The Apple evidence check on the server. Proving on an iPhone.
- Switched off Zero profiles are enabled. Every enrollment is rejected until the iPhone parts are tested.
Face ID and App Attest alone do not prove that one person has one credential. The scenarios above are a plain-language reading of the project docs. They are not the specification.
Words used on this page
- Nullifier
- The public number that names a credential. The same enrolled key always gives the same number.
- Credential
- An entry in Ser’s public book. Anyone can look it up. Looking it up does not prove who holds it.
- Secure Enclave
- A protected part of the iPhone. It keeps a key and signs with it. The key cannot be copied out.
- Holder key
- The P-256 key in the Secure Enclave. Face ID unlocks it for each signature.
- App Attest
- An Apple service. It gives a statement that a genuine copy of an app made a request. It uses a separate key.
- Challenge
- A fresh, one-time request from Ser. It has a random ID, a random nonce and a 2-minute expiry.
- Nonce
- A random number used once.
- Audience
- Who a signature is meant for, such as one app. It stops a signature from working somewhere else.
- Presentation
- A fresh Face ID signature for one app. It shows that the holder is present now.
- Profile
- A rule set in the server’s own configuration. It says which checks and which pinned key apply.
- Zero-knowledge (ZK) proof
- A proof of a fact that hides some of the inputs.
- Pseudonym
- A name for Alice that works in one app only. Other apps get a different one.