Privacy

Well, we'd be back to the 80s and I'd ask my parents about life back then. Online banking would cease to exist and I have to go to the bank teller's window to get or transfer money, also shops probably fall back to cash only. I'd need to open and start my car with a key unless that kind of cryptography is still okay and it's just phones... I'd plug my laptop and smartphone in with a network cable becase I'd be afraid the neighbours commit crimes with my Wifi... My employer might want to resort to paper instead of computers because there isn't any authentication for the company's data... I could cancel my Netflix and Spotify subscriptions because they'd either cease to exist, or I could just watch them without paying. I'd talk to my wife in the evening instead of arrange stuff via an instant messenger... I guess all of that is doable. People did it that way a while ago. It just needs restructuring of the entire economy, society and our lifes would lack most of the modern convenience. (And if it's just phones and every other cryptography is fine, I'd just get rid of the thing and use my laptop or whatever is still allowed for everything.)

And since the question was about the gameplan... First thing, I'd invest all my money into copper and fibre optic companies immediately, because people will need to install A LOT of additional, direct cables between things.