Quipu: post-quantum encryption in pure Rust, with a Python wheel

#cryptography #rust #security #postquantum

Protecting data that must stay secret ten years from now is a problem for today: an adversary can capture your encrypted traffic now and decrypt it once quantum capability exists (harvest now, decrypt later). Quipu is a free hybrid post-quantum encryption library for data at rest: it combines proven classical cryptography with the new kind, so that it only breaks if both fall at once.

Pure Rust, and why

Quipu started out aiming at several languages: a Rust core with a C ABI on top and bindings for Python, Node and Go. It worked, but the lesson was clear: maintaining a stable C interface plus four bindings, each with its own packaging and interoperability tests, was complexity that did not pay for itself against the real goal — protecting data at rest — and it widened the attack surface with unsafe we did not want.

Today Quipu is pure Rust: memory safe, no garbage collector, no first-party unsafe. And for people who do not write Rust, it ships as a native Python wheel via PyO3 — the surface that non-Rust users actually need. One codebase, one thing to audit. It is the same philosophy that guides the rest: where good cryptography exists, reuse it; simplicity is a security decision, not a convenience.

Installation

cargo add quipu              # Rust
pip install quipu-crypto     # Python (native wheel, PyO3)

Encrypt and decrypt in Python

import quipu

# Symmetric, with a passphrase
blob = quipu.encrypt_stream(b"sensitive data", "my-passphrase")
assert quipu.decrypt_stream(blob, "my-passphrase") == b"sensitive data"

# Post-quantum, for a recipient
pub, sec = quipu.generate_keypair()          # X25519 + ML-KEM-1024
c = quipu.encode_to_recipient(b"secret", pub)
assert quipu.decode_as_recipient(c, sec) == b"secret"

What is underneath

Encryption: XChaCha20-Poly1305 (authenticated AEAD).
Key derivation: Argon2id (brute-force resistant) + HKDF.
Post-quantum: X25519 + ML-KEM-1024 for keys; Ed25519 + ML-DSA-87 for signatures.
Security level: NIST category 5 (CNSA 2.0).

These are all standard, verified primitives — the ML-KEM-1024 and ML-DSA-87 known-answer tests run against NIST's official ACVP vectors. Quipu composes them; it does not invent its own cryptography.

Free and transparent

Quipu is open source (AGPL-3.0). You can read every line and audit the format, which is specified byte by byte. It is published on crates.io and, as a Python wheel, on PyPI.

Honest status: the composition has not yet passed an independent cryptographic audit. Until that external seal exists, treat it as software for review and experimentation, not for protecting real high-value secrets.

The code is at github.com/isazajuancarlos/quipu.

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