How can I calculate the signature?

1. Enter your JSON payload in the left box;
2. Enter the signature you have calculated (for checking);
3. Enter your private API Key (it starts with YGOPK-);
4. Enter the sent_at parameter (UNIX timestamp in MS);
5. Hit Calcualte;
6. See the expected signate and an indicator telling you if your pre-calculated signature is the same.