You can now activate Google's highest account protection system without spending around $50 on two security keys. Instead, all you'll need is a smartphone.

On Wednesday, the company lowered the barrier to enroll in Google's free Advanced Protection Program, which is designed to stop the most sophisticated hackers from breaking into your Gmail and Google Drive accounts.

Introduced back in 2017, the program goes beyond using digital passwords and two-factor authentication codes. Instead, it calls for a physical piece of hardware to unlock access: a security key, which can store a unique passcode to sign the authentication request over USB or a Bluetooth connection.

So if hackers ever want to hijack your account, they'll need to physically come and steal your security key. In addition, the same device will only authenticate requests binded to the official login portal, so look-alike phishing pages from cybercriminals won't be able to fool it.

The only problem with the approach is how security keys aren't exactly cheap; the prices can reach around $20 or more for each, and originally the Advanced Protection Program required users to own two keys to enroll. However, Google has come up with a way to simplify the program by getting the smartphone to act as a substitute key.

Last April, the company brought the functionality to smartphones running Android 7.0 and up. And finally today, Google announced it had expanded the security key capability to Apple iPhones running iOS 10.0 and higher. "Everything becomes much simpler when the things we're already carrying around —our smartphones— have a built-in security key," wrote Shuvo Chatterjee, Google product manager in a Wednesday blog post.

The company has published a separate blog post outlining the steps to enroll in the Advanced Protection Program with your phone. The technology works by taking the unique passcode normally stored on the security key and instead placing it in your smartphone's processor. The authentication request can then be transmitted via your phone's Bluetooth connection to verify any new login requests you make on a Windows, Mac, Chrome OS, or iOS device.

Once you're enrolled in the program, the sign-in process itself is pretty straight forward. You'll need to first type in your password. Google's login portal will then ask that your smartphone authenticate the request. As it does so, your phone (assuming its nearby and has the Bluetooth connectivity activated) should show a prompt asking you to approve the login.

Although Google is making the program easier to activate, it does come with some restrictions. For instance, the program will stop most third-party apps and services from accessing your Gmail and Google Drive data as a safeguard to prevent hijacking attempts. Another potential inconvenience is if you lose your phone. Google director Mark Risher said ideally users will buy a security key to act as a backup, but added: "We now preserve your existing (Google) sessions, so if you have a phone+laptop you should be able to recover from one to the other."

To enable the functionality, iPhone users will need to download Google's Smart Lock app, whereas Android owners don't. The company has an FAQ about the Advanced Protection Program to help users learn more. If you feel it's too much of hassle, it's a good idea to at least turn on the two-factor authentication on all your valuable online accounts. This can make it harder for hackers to break in if they ever learn your passwords.