private string CreateSignature(string message)
{
var hash256Bytes = sha256_hash(message);
var urlBytes = StringToByteArray(_fullUrl);
var messageAndUrlByteArray = ByteArrayHelper.CombineByteArrays(urlBytes, hash256Bytes);
var signature = getHash(StringToByteArray(_apiSecret), messageAndUrlByteArray);
var base64EncodedSignature = Convert.ToBase64String(signature);
return(base64EncodedSignature);
}