Sortes — true ECVRF verifiable-randomness oracle

Sortes draws lots you can verify. It is a true Verifiable Random Function implementing ECVRF-EDWARDS25519-SHA512-TAI exactly per RFC 9381 (suite octet 0x03, over the edwards25519 curve).

For a fixed (public_key, alpha) there is exactly one valid output beta. The oracle's secret key selects it deterministically, so — unlike a trusted randomness beacon — the oracle cannot grind or bias the result, and anyone holding the VRF public key can verify the draw offline from the 80-byte proof.

Capabilities

alpha is UTF-8 by default; prefix with hex: to pass raw bytes.

Why it is correct

The implementation is pure Python (hashlib + integer math) — the edwards25519 group arithmetic (RFC 8032 §5.1) and the ECVRF construction (RFC 9381 §5) are written from scratch, no external crypto libraries. Correctness is proven by the RFC 9381 Appendix B.3 test vectors: the tests assert that our implementation reproduces the published SK→PK, the hash-to-curve point H, the proof commitment Gamma, the VRF output beta, and the full 80-byte proof pi byte-for-byte for all three vectors. The full-pi check pins the little-endian c || s encoding mandated by RFC 9381 §5.5, so the proofs are byte-interoperable with a conformant verifier (e.g. libsodium), not merely self-consistent; the tests also confirm the RFC's own published pi bytes verify under our verifier. See tests/test_sortes.py.

VRF keypair

The oracle holds one VRF keypair. The 32-byte secret key is resolved from SORTES_VRF_SK (64 hex chars), else a persisted key at SORTES_VRF_SK_PATH (default data/sortes_vrf_sk), else generated once and persisted so the public key stays stable across restarts. The secret key never leaves the process; the public key is published in every draw and in the manifest description.

Run

# tests (from the monorepo root)
PYTHONPATH="oracles/core:oracles/oracles/sortes" \
  platon/backend/.venv/bin/python -m pytest oracles/oracles/sortes/tests/ -q

# serve (port 9310 by default)
PYTHONPATH="oracles/core:oracles/oracles/sortes" python -m sortes.main

Environment