What phone app? If it is the security key , I didn't know it was free. What if I don't have a cell phone? I do have an iphone, but how did you know that?
If the security key is free on the iphone and I don't have to pay for it, then I may download it.. but that doesn't keep this new system from being annoying.
Seriously??? It's right there on the log-in page. "What is this?" is linked right at the Security Key entry space.
Reading is fundamental.