libsoliton

Pure-Rust post-quantum cryptographic library for end-to-end encrypted communications.

What It Does

libsoliton implements a complete cryptographic protocol stack for applications that need end-to-end encryption resistant to both classical and quantum adversaries:

• Composite identity keys — X-Wing (X25519 + ML-KEM-768) for key encapsulation, Ed25519 + ML-DSA-65 for signatures. Every identity operation uses both a classical and post-quantum algorithm; both must succeed.
• Asynchronous key exchange (LO-KEX) — a KEM-based protocol analogous to X3DH but built on encapsulation rather than Diffie-Hellman. Supports offline recipients via pre-key bundles.
• Double ratchet (LO-Ratchet) — forward-secret, post-compromise-secure message encryption using X-Wing KEM ratchet steps and HKDF-SHA3-256 chain derivation.
• Encrypted storage — Argon2id-protected key vaults with XChaCha20-Poly1305 and zstd compression.
• Streaming AEAD — chunked encryption for large payloads (files, media) with random-access decrypt support.
• KEM-based authentication — zero-knowledge proof of identity key possession without revealing the key.

Why It Exists

The "harvest now, decrypt later" threat is real: adversaries are collecting encrypted traffic today with the expectation that future quantum computers will break classical key exchange. Encrypted messaging, file storage, and voice/video calls established with ECDH or RSA key agreement are retroactively compromised the moment a sufficiently powerful quantum computer comes online.

libsoliton pairs every classical primitive with a NIST-standardized post-quantum counterpart — ML-KEM-768 for key encapsulation (FIPS 203), ML-DSA-65 for signatures (FIPS 204) — so that the system remains secure even if one algorithm family is completely broken.

This is not speculative. NIST finalized ML-KEM and ML-DSA in 2024. X-Wing, the hybrid KEM construction, is an active IETF draft (draft-connolly-cfrg-xwing-kem-09). The post-quantum transition is happening now; libsoliton is built to be used now.

Who It's For

Developers building applications that require end-to-end encryption and want post-quantum security without depending on C toolchains, system OpenSSL installations, or assembly-language cryptographic backends.

• End-to-end encrypted messaging (the primary target)
• Encrypted voice and video calls (call key derivation from ratchet state)
• Encrypted cloud storage and file transfer
• Password-protected key vaults
• Zero-knowledge authentication

Design Principles

Principle	Implementation
Pure Rust, zero C dependencies	All cryptographic backends are Rust crates from RustCrypto and dalek-cryptography. No cmake, no system linker dependencies, no vendored C.
Hybrid everywhere	Every key exchange uses X-Wing (X25519 + ML-KEM-768). Every signature uses Ed25519 + ML-DSA-65. Both components must succeed — no fallback to classical-only.
Constant-time by construction	XChaCha20-Poly1305 uses ARX operations only — no table lookups, no secret-dependent branches. No hardware acceleration required.
Defense in depth	Ratchet state snapshot/rollback on AEAD failure. Zeroization of all secret key material. Domain-separated KDF with unique labels per derivation context.
Single audit point	All language bindings call through one C ABI layer into the same Rust implementation. One codebase to audit.

At a Glance

Primitive	Algorithm	Key / Output Size
Identity KEM	X-Wing (X25519 + ML-KEM-768)	1216 B pk / 2432 B sk
Identity Signing	Ed25519 + ML-DSA-65	3373 B hybrid signature
Symmetric AEAD	XChaCha20-Poly1305	256-bit key / 128-bit tag
Hash	SHA3-256 (FIPS 202)	32 B
KDF	HKDF-SHA3-256	Variable (max 8160 B)
Streaming AEAD	XChaCha20-Poly1305, counter nonces	1 MiB chunks
Password KDF	Argon2id (RFC 9106)	Configurable output

Crate Layout

Package	Path	Purpose
libsoliton (crates.io)	soliton/	Core library — all cryptographic logic
libsoliton_capi (crates.io)	soliton_capi/	C ABI FFI layer (cbindgen-generated header)
soliton-py (PyPI)	soliton_py/	Python binding (PyO3/maturin)
soliton-wasm (npm)	soliton_wasm/	WASM binding (wasm-bindgen)
soliton-cli (cargo)	soliton_cli/	Native CLI
soliton_zig	soliton_zig/	Zig wrapper (consumes CAPI via @cImport)

Performance

Operation	Desktop	RPi 5	VisionFive 2
Ratchet encrypt (same direction)	4.3 µs	7.2 µs	47.6 µs
Ratchet encrypt (direction change)	182 µs	651 µs	2.46 ms
Session establishment (initiator)	1.41 ms	3.95 ms	17.1 ms
Session establishment (responder)	585 µs	1.88 ms	7.70 ms
Streaming encrypt (1 MiB)	537 µs	3.96 ms	31.0 ms

Desktop: AMD Ryzen 7 7840HS (Zen 4). RPi 5: Cortex-A76. VisionFive 2: SiFive U74 (RISC-V). See Audit & Testing for full benchmark tables.

Source & Packages

• git.lo.sh/lo/libsoliton — source repository
• docs.rs/libsoliton — Rust API documentation
• pypi.org/project/soliton — Python package
• npmjs.com/package/soliton-wasm — WASM package