decrypt method
Implementation
@override
Future<String> decrypt(String symKey, String encoded) async {
final chacha = dc.Chacha20.poly1305Aead();
final dc.SecretKey secretKey = dc.SecretKey(
hex.decode(symKey),
);
final EncodingParams encodedData = deserialize(encoded);
final dc.SecretBox b = dc.SecretBox.fromConcatenation(
encodedData.ivSealed,
nonceLength: 12,
macLength: 16,
);
List<int> data = await chacha.decrypt(b, secretKey: secretKey);
return utf8.decode(data);
}