I have a situation where iPhone client Signs In with Google/Facebook
step 1
iPhone Client --------——> Google/Facebook
Once Authenticated, client needs to get data from my REST APIs
step 1
iPhone Client --------——> Google/Facebook
|
| step 2
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V
GET /transactions
Question
Since server is not aware if client is authenticated(Ideally client is authenticated), what are some ways I can secure my REST APIs to have confidence that it is reasonably secured against malicious attacks?
Also, I do not want to maintain user/passwords on server