The sign data is made up out of multiple input fields, those are specified on the concerned API specification page.
Sort the sign data alphabetical ascending, you can also find the sequence on the concerned API specification page.
The HMAC Key is generated using the HMAC method with SHA256 as algorithm, afterwards the HMAC Key is base64-encoded.
Please note: never include your apiSecret (private key) in requests.
In this generator we will use getAvailableUsers as example.