All QUODD financial data APIs can be called securely over HTTPS using SSL. The implementation of secure calls varies depending on the client's protocol (SOAP vs. REST).
If you are using SOAP, you simply need to make sure you use a secure web reference to the WSDL file. Please find the relevant WSDL for the service in the API Test Form, under the 'Code' tab on any of the APIs in our catalog.
For REST, please add HTTPS as the prefix to your url instead of HTTP to make the call secure. The APIs will work exactly the same way regardless of the prefix.