newKeyPairFromSeed method

@override Future<EcKeyPair> newKeyPairFromSeed(List<int> seed)

Generates a key pair from the seed.

This will throw UnsupportedError if the algorithm does not support seeds for private key generation.

Example

In this example, we use X25519:

import 'dart:convert';
import 'package:cryptography/cryptography.dart';

Future<void> main() async {
  // X25519 seed is any 32 bytes.
  // We can use SHA256, which computes a 32-byte hash from any input.
  final seed = utf8.encode('example');
  final seedWith32Bytes = (await Sha256().hash(seed)).bytes;

  final algorithm = X25519();
  final keyPair = await algorithm.newKeyPairFromSeed(seedWith32Bytes);
}

Implementation

@override
Future<EcKeyPair> newKeyPairFromSeed(List<int> seed) async {
  if (isSupportedPlatform) {
    final result = await invokeMethod(
      'Ecdh.newKeyPair',
      {
        if (isAndroid) 'androidProvider': androidCryptoProvider,
        'curve': _curveName,
        'seed': asUint8List(seed),
      },
    );
    final der = result['der'] as Uint8List?;
    if (der != null) {
      return EcKeyPairData.parseDer(
        der,
        type: keyPairType,
      );
    }
    final d = result['d'] as Uint8List;
    final x = result['x'] as Uint8List;
    final y = result['y'] as Uint8List;
    return EcKeyPairData(
      d: d,
      x: x,
      y: y,
      type: keyPairType,
    );
  }
  final fallback = this.fallback;
  if (fallback == null) {
    throw UnsupportedError('Unsupported and no fallback implementation');
  }
  return await fallback.newKeyPair();
}