Functionality
Basically, Coin Auth works by requesting the CoinHive to load their mining script on your WordPress login page. This is visually similar to reCaptcha and once someone clicks on the ‘Verify’ checkbox, their device is using its computing power in hashing Monero(XMR) cryptocurrency.

To do this, first you’ll need to install the plugin from wordpress.org and get a CoinHive account. After creating your account, get your public and private key from the Sites & API keys page and enter it inside Coin Auth’s dashboard. This is located inside Settings > Coin Auth.

There’s also an option to whitelist IP’s and a handy Monero conversion box on the right.
After setting it up, you’ll get the Verification box on the login page. On a fairly decent computer(I’m running a Razer Blade 14), it takes about 3-5 seconds to process 256 hashes. It does get visibly laggy during those few seconds.
The best thing is how easy it is to setup Coin Hive. Once you start earning sufficient Monero you can put your payment address inside CoinHive’s dashboard to receive payments.