Concepts

Freebird is a Rust service pair for issuing and redeeming privacy-preserving tokens. A client submits a blinded request to an issuer, finishes the token locally, and later presents it to a verifier. The verifier validates the token and atomically records a spend handle.

The implemented token families are:

• V4: a Freebird-specific, bespoke P-256 VOPRF-like private-verification construction. It is not RFC 9497 or Privacy Pass interoperable.
• V7: native bearer tokens using randomized RSA blind signatures and issuer-published discovery metadata.

V5 and V2 are removed and rejected. V6 is reserved and rejected. Start with issuers, verifiers, and tokens, then follow the protocol overview.

Status vocabulary

These pages use implemented for behavior present in the current source, expected for an operator or client requirement stated by current documentation, and future for material that is not a current protocol contract. Future interoperability or profile work requires maintainer review.

Security boundaries and deployment assumptions are summarized in the threat model and production deployment baseline.