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

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.