The name and the crest
Light, and what you draw across it.
Lumo is light. A veil is the thing you put between the light and everyone else — not a wall, not a disguise, just a layer that decides who gets to see.
The mark is a heraldic one, which is deliberate. Heraldry was a system for making a claim in public and being held to it: a crest was a promise about who you were, displayed where everyone could check it. That is an unfashionably good model for a privacy company. The lion is the guardian. The shield is the boundary. The lock is the mechanism. Nothing in it is metaphorical about what the app does.
The gold rule that runs through this site is the same idea in a quieter form: a line you can see, drawn on purpose, in the same place every time.