Threshold Passport Identification

Match passports or any identification document (e.g. national IDs) across parties without revealing the underlying document data.

The tracability problem of digital identities

Identity documents like passports or national identity cards are the defacto standard to authenticate an individual in the physical world. This property makes them a natural anchor for digital identity systems as well. But operating on these data digitally requires careful handling: the underlying attributes are sensitive, tied to a real person, and cannot be rotated if compromised.

A common mitigation is to avoid publishing the plain data in the first place. Instead the data is hashed before being posted and used for identity comparison. The raw document data is never transmitted. This limits casual observers - but not the issuers or anyone else with access to the raw data. Issuing authorities might hold the original data and can compute the same hashes, making users traceable to any party that issued their document.

Unique and unlinkable identities

TACEO:OPRF computes a nullifier over the document hash using a threshold of independent MPC nodes. The resulting nullifier is deterministic - it uniquely identifies the user - but no single party, including TACEO or the document issuer, can compute it unilaterally. Knowledge of the document's pre-image is no longer sufficient to derive or link the identifier.