x448_dart 0.2.0

X448 (RFC 7748) Elliptic-Curve Diffie-Hellman for Dart/Flutter with FlutterFlow-friendly base64 helpers.

x448_dart

Cross‑platform X448 (RFC 7748) Elliptic‑Curve Diffie–Hellman for Dart, Flutter, and FlutterFlow.

This package provides secure key generation, public key derivation, and shared secret computation with optional HKDF‑SHA512 and memory zeroization utilities. Constant‑time implementations are supplied via FFI (OpenSSL/BoringSSL) and WebAssembly, with a pure Dart fallback for platforms where a constant‑time backend is unavailable.

Features

• ✈️ Cross‑platform: Android, iOS, macOS, Windows, Linux, Web, and Dart CLI
• 🔒 Constant‑time backends with optional enforcement via X448.requireConstantTime
• 🧪 RFC 7748 test vectors included
• 🔍 HKDF‑SHA512 helper (hkdfSha512) and FlutterFlow‑friendly Base64 wrappers
• 🗑️ Zeroization helpers (zeroize, withSharedSecret) to wipe secrets from memory

Security

Set X448.requireConstantTime = true; before calling APIs to require a constant‑time backend. If none is available, the methods throw StateError. Without this flag the library falls back to a pure Dart implementation that is not constant‑time.

Platform matrix

Platform	Backend	Constant-time
Android / iOS	FFI (BoringSSL)	✅
macOS / Windows / Linux	FFI (OpenSSL)	✅
Web	WebAssembly	✅
Dart VM fallback	Pure Dart	❌

Usage

import 'dart:convert';
import 'package:x448_dart/x448.dart';

Future<void> main() async {
  final alice = await X448.generate();
  final bob   = await X448.generate();

  final s1 = X448.sharedSecret(
    privateKey: alice.privateKey,
    peerPublicKey: bob.publicKey,
  );
  final s2 = X448.sharedSecret(
    privateKey: bob.privateKey,
    peerPublicKey: alice.publicKey,
  );

  print('Equal? ${base64Encode(s1) == base64Encode(s2)}'); // true
}

FlutterFlow helpers

flutterflow_x448.dart and flutterflow_hkdf.dart expose Base64‑friendly wrappers for FlutterFlow custom actions.

License

MIT