Need API (HMAC) capable IOS functionality built – Swift -- 2

We need an expert iOS developer to build initial API capability for an iOS app. App will connect to backend API server using HMAC authentication (public and private key stored in app). Need developer to setup necessary delegates for the APP to call the API server. Each request need to send a payload, nonce, timestamp and public key. API connection functionality needs to be contained in it’s own class and accessible from and page.
Language : swift
Storyboard required