ZK ID Presentation

This demonstration allows you to present an identity attribute from your digital ID in Google Wallet using a Longfellow zero-knowledge (ZK) proof. This method is the most privacy-friendly way to share your identity information online.

✦ How does this work?

Google Wallet lets you manage a digital ID on your phone. Sometimes you need to prove something about yourself---like that you're over 18---but you shouldn't have to hand over your full name, address, and birthday just to do that. Longfellow is a zero-knowledge protocol that lets you prove specific facts about your identity without revealing anything else.

🪪 Your ID
Digital credential
Your phone holds a cryptographically signed digital ID (mDOC)
🔐 ZK Proof
Prove, don't reveal
Longfellow generates a proof that you meet a requirement — without exposing your data
🛡️ Verified
Verifier is convinced
The verifier can confirm the proof is valid, but learns nothing else about you

The privacy guarantee: the verifier learns only what you choose to share (e.g., "age ≥ 18") and nothing more: not your name, not your birthday, not your address. This is possible by the mathematical properties of zero-knowledge.

Without zero-knowledge protocols, schemes like mdoc and SD-JWT have privacy flaws that inadvertently allow relying parties or issuers to track your activity. To bridge these gaps, we're building tools and systems that make ZK more widely understood, customizable and generally capable.

Read the paper Documentation IETF Draft