zkDPoP-Go

A Golang framework for zero-knowledge Demonstration of Proof-of-Possession (zkDPoP) authentication using interactive Schnorr signatures with sender-constrained JWTs.

Features

• Interactive Schnorr ZK login over secp256k1 or ristretto255
• Issues short-lived, DPoP-bound JWTs (5-15 minutes)
• Sender-constrained tokens via cnf.jkt binding to DPoP keys
• Per-request DPoP verification middleware
• Stateless resource servers (validate JWT + DPoP without ZK knowledge)
• Clean extension points for broader ZK authorization
• Comprehensive security hardening (replay protection, tight windows, configurable rate limits)

Architecture

+------------------+          +---------------------+         +-------------------+
|  Client          |          |  Auth Server        |         |  Resource Server  |
|  (DPoP keypair)  |          |  (zkDPoP AuthZ)     |         |  (API + middleware)|
+---------+--------+          +----------+----------+         +---------+---------+
          |                               |                              |
(1) POST /auth/zk/commit  DPoP proof ---> |                              |
          | <--- (2) c, timeslice, server_ephemeral                      |
(3) POST /auth/zk/complete  + s  DPoP --->|  verify schnorr & DPoP       |
          | <--- (4) JWT {cnf.jkt=thumb(DPoP JWK)}                       |
          |                               |                              |
          | --- API call --- DPoP + JWT -------------------------------> | verify DPoP + JWT
          |                               |                              |

Quick Start

# Start auth server
go run ./cmd/zkdpop-authd

# Start demo API server  
go run ./cmd/zkdpop-demo-api

# Run example client
go run ./examples/client-go

# Use the Ristretto255 group instead of secp256k1
go run ./cmd/zkdpop-authd --curve ristretto255
go run ./examples/client-go --curve ristretto255

Both servers expose a --rate-limit flag (requests per minute per client). The default of 120 for the authd binary and 240 for the demo API keeps login flows responsive while guarding against brute-force attempts.

Project Structure

• cmd/zkdpop-authd - Reference auth server
• cmd/zkdpop-demo-api - Example resource server
• pkg/crypto/ - Curve interfaces and Schnorr verification
• pkg/dpop/ - DPoP proof verification and JWK thumbprints
• pkg/jwt/ - JWT minting/verification with cnf.jkt binding
• pkg/auth/ - Auth handlers for ZK login endpoints
• pkg/storage/ - Storage interfaces and implementations
• pkg/middleware/ - HTTP middleware for DPoP and JWT verification
• examples/client-go/ - Sample client implementation

Standards Compliance

• RFC 9449 - DPoP - Demonstration of Proof-of-Possession
• RFC 7800 - JWT Proof-of-Possession - cnf.jkt binding
• RFC 7638 - JWK Thumbprints - JWK SHA-256 thumbprints

License

MIT