🕊️ Freebird

The Problem

The internet has a surveillance problem baked into its infrastructure. Not because of malicious actors, but because useful systems require identity by default.

• Rate limiting requires tracking users
• Access control requires accounts
• Spam prevention requires surveillance
• Resource allocation requires registration
• "One person, one vote" requires identity databases

Even privacy-respecting services must collect your data to function. The architecture demands it.

Traditional System:

User ──────────────────────────▶ Server
      "I am alice@example.com"
      "Give me access"
                                    │
Server logs:                        ▼
✗ Who you are                    Access
✗ When you accessed              Granted
✗ What you accessed              (maybe)
✗ Your usage patterns
✗ Your IP address
✗ Everything, forever

Freebird's Answer

Freebird supports two token modes that achieve the same unlinkability guarantee via different cryptographic paths: VOPRF (Verifiable Oblivious Pseudorandom Function over P-256, with DLEQ proofs) for issuer-blinded tokens, and Blind RSA (RFC 9474) for public bearer passes. Both separate "can you?" from "who are you?" for the first time in a practical, deployable way.

Think of it as anonymous digital cash for authorization. Users receive unforgeable, unlinkable tokens that prove permission while revealing nothing about identity.

Freebird:

        ┌─────────────────────────────────────────────────────────┐
        │                                                         │
        │   User              Issuer              Verifier        │
        │     │                 │                    │            │
        │     │──[blind data]──▶│                    │            │
        │     │                 │ signs without      │            │
        │     │                 │ seeing content     │            │
        │     │◀─[signed blob]──│                    │            │
        │     │                 │                    │            │
        │     │ unblinds to     │                    │            │
        │     │ get token       │                    │            │
        │     │                 │                    │            │
        │     │──────────[anonymous token]──────────▶│            │
        │     │                                      │            │
        │     │                              ✓ Valid signature    │
        │     │                              ✗ No identity        │
        │     │                              ✗ No tracking        │
        │                                                         │
        └─────────────────────────────────────────────────────────┘

Issuer sees: Someone requested a token. (Nothing else.)
Verifier sees: Valid token from trusted issuer. (Nothing else.)
Correlation: Mathematically impossible.

• Prove you're authorized without revealing who you are
• Rate limiting without tracking
• Access control without accounts
• Spam prevention without surveillance
• One person, one vote—anonymously

Cryptographic Guarantees

Not privacy theater. Not "we promise not to look." Mathematical impossibility of surveillance.

Real-World Applications

Freebird solves concrete problems for municipalities, healthcare systems, educators, and communities.

Sybil Resistance

Freebird includes multiple mechanisms to prevent abuse without surveillance:

Invitation System (Trust Graphs)

Users invite others. Abuse traces back through the invitation chain. Bad actors get cut off—along with everyone they invited. Social accountability without identity.

Proof of Work

Computational cost per token. Prevents bot farms without collecting data.

WebAuthn / Hardware Keys

"Proof of humanity" via hardware authenticators. No biometrics stored, no accounts created.

Rate Limiting

IP-based throttling for basic protection. Stackable with other mechanisms.

Social Graph Attestation

A separate Social Graph Attester service evaluates signed trust edges (Clout-style) and issues short-lived attestations proving a user stands within a trusted social graph, without revealing which node they are. The issuer verifies the attester's Ed25519 signature, policy, expiry, and eligibility level — never the underlying graph.

Progressive Trust

Trust accumulates with account age and usage history. New accounts get limited quotas; established accounts get more. No identity stored — just a counter.

Proof of Diversity

Experimental mechanism that scores requests on behavioral diversity signals to detect coordinated bot campaigns without fingerprinting individuals.

Multi-Party Vouching

N-of-M endorsement: a token is issued only when a quorum of existing trusted members vouch for the requester. No single party can approve or block.

Composable Combiners

Stack mechanisms with OR (any must pass), AND (all must pass), or Threshold (at least N of M). OR is only as strong as the easiest mechanism; AND is strictest. One proof satisfies exactly one mechanism — duplicate proofs can't be replayed across gates.

Technical Architecture

┌─────────────────────────────────────────────────────────────────────┐
│                         Freebird System                             │
│                                                                     │
│   ┌──────────────┐  ┌──────────────┐  ┌────────────┐  ┌─────────┐  │
│   │    Issuer    │  │   Verifier   │  │   Redis     │  │ Attester│  │
│   │   (Rust)     │  │   (Rust)     │  │  (State)    │  │ (Rust)  │  │
│   │              │  │              │  │            │  │ optional│  │
│   │ - VOPRF eval │  │ - Token auth │  │ - Nulls    │  │ - Trust │  │
│   │ - Blind RSA  │  │ - Multi-     │  │ - Invites  │  │   graph │  │
│   │ - Sybil gates│  │   issuer     │  │ - WebAuthn │  │ - Scoring│ │
│   │ - Key mgmt   │  │   federation │  │            │  │ - JWKS  │  │
│   └──────────────┘  └──────────────┘  └────────────┘  └─────────┘  │
│          │                  │                 │              │      │
│          └──────────────────┴─────────────────┘              │      │
│                             │                                 │      │
│                    ┌────────▼────────┐                        │      │
│                    │   TypeScript    │◀───────────────────────┘      │
│                    │      SDK        │                               │
│                    │                 │                               │
│                    │ Browser/Node.js │                               │
│                    └─────────────────┘                               │
└─────────────────────────────────────────────────────────────────────┘

Implementation Status

Why Open Infrastructure Matters

Privacy technology that requires trusting a company is privacy theater. Freebird is infrastructure, not a service.

• Self-hostable: Run your own issuer. No dependencies on us.
• Federated: Multiple issuers can exist. Verifiers choose whom to trust.
• Auditable: Every line of code is public. Every cryptographic claim is verifiable.
• Forkable: Don't like our decisions? Fork it. The protocol is the product.

Funding Goals

Freebird's core technology works. Funding accelerates adoption and hardening.

Try It

git clone https://git.carpocratian.org/sibyl/freebird
cd freebird
./launch.sh up

The launch.sh helper handles .env setup and ADMIN_API_KEY generation for you. Issuer on localhost:8081, verifier on localhost:8082.

# Get a token
curl -X POST http://localhost:8081/v1/oprf/issue \
  -H "Content-Type: application/json" \
  -d '{"blinded_element": "..."}'

# Verify it
curl -X POST http://localhost:8082/v1/verify \
  -H "Content-Type: application/json" \
  -d '{"token": "..."}'

Full documentation at git.carpocratian.org/sibyl/freebird/docs.

Standards & Prior Art

Freebird implements established cryptographic standards:

• IETF CFRG VOPRF Draft — The core protocol
• Privacy Pass Protocol — Related work from Cloudflare/Apple
• RFC 9474 — Blind RSA signatures (V5 public bearer passes)
• RFC 9380 — Hash-to-curve specification
• FIPS 186-5 — P-256 curve specification