How to enable two-step verification in WhatsApp for Apple's iPhone

Within the app, first tap on the Settings tab, then on Account. You should then see a Two-Step Verification option, through which you can choose to begin the setup process.

The app will prompt you to enter and then re-enter a six-digit passcode. You can also choose to enter an email address as backup, though WhatsApp notes that it will only send a link to disable two-step verification.

It's important to use a legitimate, easily-accessed email address, because failing to do so could potentially lock you out of your account.

Once two-step verification is on, a phone number can't be reverified in WhatsApp within seven days of last using the app without the appropriate passcode. A passcode isn't required past the seven-day mark, but if you go that route, all pending messages will be deleted.

If a number is reverfied without a passcode after 30 days, WhatsApp will simply delete the associated account outright, and create a new one.

Because of risks involved in forgetting your passcode, the app will periodically ask you for it regardless. This can only be stopped by turning two-step verification off via the same menu as before, which also offers options for changing your passcode or backup email.