How to Authorize REST API Requests using GroupDocs.Viewer Cloud API

Hi There,
What is signature parameter in url while testing here: GroupDocs.Viewer for Cloud - API References

Every time new signature is coming in url how can I use that on rest client or on any other portal to access the APIs.

Because when I have registered for free trial I got only SID and appkey
And I am passing it url so getting auth failure error.
Please help me asap.

@DemoTestUser

Thanks for your inquiry. Please note you need to authenticate GroupDocs for Cloud REST APIs request using OAuth 2.0 protocol or URL Signing method. When using URL Signing option to authenticate REST APIs request, you need to pass a HMAC-SHA1 signature parameter generated by using your private key. Please check the documentation to sign the request url along with following resources for more details. Please also find a sample code snippet (2.1 KB) for more details.

Please feel free to contact us for any further assistance.