For that , you have to change the "Security" settings of endpoint in SOAMANAGER .
Open SOAMANAGER , select the service , click on configuration , edit the service point, click on Security tab ,
change the " Transport Protocol" from HTTP to HTTPS .
Now save the changes.
After saving It will also reflected in SICF.
It is indeed possible.
If HTTPS is activated in your ICM on port xxx, just change your REST service URL to https://host:xxx.
Did you develop an abap HTTP handler for you REST service or did you use the SAP Netweaver Gateway ?