WhatsApp has updated its android beta app to version 2.19.83, and traces of a new Authentication feature were spotted.
the company has been acting on bringing this feature since a while currently, and the latest update shows that WhatsApp has made a lot of progress.
Beta tracker WABetaInfo has shared screenshots showing however the Authentication feature is enabled in Settings, and what the interface can seem like. 
unfortunately, this feature is disabled by default, thus it will not work for beta users as of yet. It remains unclear once WhatsApp plans to roll it out for the stable version users.
The tracker says that the Authentication feature can let WhatsApp users lock their account, and unlock it employing a fingerprint sensor.
This feature ought to be enabled in Settings >Account >Privacy > Use Fingerprint to Unlock. Once it’s enabled, WhatsApp can register your fingerprint. it’ll then raise if you want the app to be locked immediately.
WhatsApp can show a sign indicating to users that they has to unlock the app using fingerprint authentication. it’ll show an error if the app isn’t unlocked once multiple tries.
As mentioned, this feature is not enabled nonetheless, thus you will not see it even if you’re on the latest beta version 2.19.83. This feature ought to roll out for beta users in next updates.
Notably, iPhone users already have the feature within the stable version of the iOS app, and apart from fingerprint authentication via touch ID, facial recognition via Face ID is additionally available to them.
WhatsApp is additionally working on Dark Mode, and it had been spotted in one among the recent beta updates. However, there’s no word on once the WhatsApp Dark Mode can create its way to the stable version. Recent beta versions also indicate that WhatsApp is working new forwarding features as well.
