When the Mangalores meet with Zorg to deliver (what they think are) the stones, their leader Aknar is wearing a human disguise. The exact nature of the speculative technology is difficult to determine. (In fact, it’s entirely arguable that this is a biological ability, but it’s more useful to presume it’s not.)
Zorg tells Aknar, “What is that you? What an ugly face. It doesn’t suit you. Take it off.” Aknar strains his chin upward and shakes his head rapidly. As he does so, the disguise fades to reveal his true face.
Presuming it’s a technology, the gesture is a nice design choice for the interaction. It’s not a gesture that’s likely to be done accidentally, and has a nice physical metaphor—that of shaking off water. The physicality makes it easy to remember. Plus, being a head gesture, it can be deployed in the field even when carrying a weapon. This makes it possible to dismiss and show your identity to comrades without the risk of lowering your guard. It does temporarily limit the wearer’s ability to sense danger, but I suspect Mangalores care more about keeping their finger on the trigger.
Of course it raises the question of whether what results from the shake is just another disguise, but that would depend on some external system of multifactor authentication that’s separate from the gesture.