swift3 - How to protect secret key

Question

I am new of iOS swift 3 development. Now, I am working on a project which needs encryption, message authentication code(MAC) and Hashed-base-MAC. These algorithms require se

Answer 1

Check iCloud Keychain (based on your tags [ios], [swift], [key]).

It functions as a secure database that allows information including a user's website login passwords, Wi-Fi network passwords, credit/debit card management (though without CVV), and other account data, to be securely stored for quick access and auto-fill on webpages and elsewhere when the user needs instant access to them. They are always stored encrypted using 256-bit AES encryption, are stored on device and pushed from iCloud between devices, and only available on a user's trusted devices.

Answer 2

Don't store the key at all. Perform a Diffie-Hellman key exchange to start an asymmetrically encrypted channel, and use this channel to send across a symmetric key to the client, which can be used for subsequent client use.