Fernet constructor

Fernet(dynamic key)

key is URL-safe base64-encoded and it has to be 32-bytes long before base64-encoding. This must be kept secret. Anyone with this key is able to create and read messages.

Implementation

Fernet(dynamic key) {
  if (key is! Uint8List && key is! String) {
    throw ArgumentError('key must be Uint8List or String');
  }
  try {
    final String keyStr = key is String ? key : utf8.decode(key);
    final Uint8List keyDecoded = base64Url.decode(keyStr);
    if (keyDecoded.length != 32) {
      throw FormatException();
    }
    _signingKey = keyDecoded.sublist(0, 16);
    _encryptionKey = keyDecoded.sublist(16, 32);
  } on FormatException {
    throw ArgumentError(
      'Fernet key must be 32 url-safe base64-encoded bytes.',
    );
  }
}