jwkToKey function

Uint8List jwkToKey(Map<String, dynamic> jwk)

Implementation

Uint8List jwkToKey(Map<String, dynamic> jwk) {
  String normalizeBase64(String base64) {
    final buffer = StringBuffer(base64);
    while (buffer.length % 4 != 0) {
      buffer.write('=');
    }
    return buffer.toString();
  }

  final String kty = jwk['kty'];
  final String crv = jwk['crv'];
  final String xBase64 = jwk['x'];
  final x = base64Url.decode(normalizeBase64(xBase64));

  if (kty == 'OKP' && crv == 'Ed25519') {
    // Ed25519 format (Curve ID = 0)
    return Uint8List.fromList([0, 0] + x);
  } else if (kty == 'EC' && (crv == 'P-256' || crv == 'secp256k1')) {
    // Extract x and y coordinates for EC keys
    final String yBase64 = jwk['y'];
    final y = base64Url.decode(normalizeBase64(yBase64));

    final curveID = (crv == 'P-256') ? 1 : 2;

    // Format: [CurveID, 0] + X + Y
    return Uint8List.fromList([curveID, 0] + x + y);
  } else {
    throw Exception('Unsupported JWK format');
  }
}