Hi Harshraj Singh,
Mendix has published a new AWS Authenticator module which has the function to Create an AWS signature.
They have also published other connectors like AWS Rekognition. Feel free to Download those modules as and check how they have implemented the signature.
AWS Authentication Connector: https://marketplace.mendix.com/link/component/120333
AWS Rekognition : https://marketplace.mendix.com/link/component/204717
To give some insight into the Signature, we have to generate the Signature beforehand and pass the signature in the custom headers in our Rest call ( In postman signature calculation is automated ).
Hope this Help!!!