Post-Quantum Cryptography in Flutter #

This repository is parameter selection and lightweight wrapper around a number of (FFI wrapped) Rust cryptographic libraries. Its purpose isn't to implement primitives, rather to unify the API surface of existing libraries; limited to the tiny subset needed by the Dark Bio project.

The library is opinionated. Parameters and primitives were selected to provide matching levels of security in a post-quantum world. APIs were designed to make the library easy to use and hard to misuse. Flexibility will always be rejected in favor of safety.

• Certificates
  • x509 (RFC-5280): xDSA, xHPKE
• Digital signatures
  • xDSA (RFC-DRAFT): MLDSA, EdDSA, SHA512
    • EdDSA (RFC-8032): Ed25519
    • MLDSA (RFC-DRAFT): Security level 3 (ML-DSA-65)
  • RSA (RFC-8017): 2048-bit, SHA256
• Encryption
  • xHPKE (RFC-9180): X-WING, HKDF, SHA256, ChaCha20, Poly1305
    • X-WING (RFC-DRAFT): MLKEM, ECC
      • ECC (RFC-7748): X25519
      • MLKEM(RFC-DRAFT): Security level 3 (ML-KEM-768)
  • STREAM (RFC N/A, Rage): ChaCha20, Poly1305, 16B tag, 64KB chunk
• Key derivation
  • Argon2 (RFC-9106): id variant
  • HKDF (RFC-5869): SHA256
• Serialization
  • CBOR¹ (RFC-8949): restricted to bool,null, integer, text, bytes, array, map[int], option
  • COSE (RFC-8152): COSE_Sign1, COSE_Encrypt0, dark-bio-v1: domain prefix

¹ As CBOR encoding/decoding would require a full reimplementation in Dart, that is delegated to any preferred 3rd party library. To ensure correctness, this package provides a cbor.verify, which it also implicitly enforces that when crossing through cose.

Native packages #

The underlying implementation exists in two sibling repos, which track the same feature set and API surfaces, released at corresponding version points.

• Rust github.com/dark-bio/crypto-rs
• Go github.com/dark-bio/crypto-go

Acknowledgements #

Shoutout to Filippo Valsorda (@filosottile) for lots of tips and nudges on what kind of cryptographic primitives to use and how to combine them properly; and also for his work in general on cryptography standards.

Naturally, many thanks to the authors of all the libraries this project depends on.