Cryptography · August 7, 2026

Why we ask you to move your mouse

When you create your vault, Privt Voice asks you to wave your mouse around while a field of characters blooms across the screen, a step that can easily look like security theatre. This post explains honestly what it accomplishes, because a privacy product that is imprecise about its own claims does not deserve your trust.

What actually happens

Your encryption keys need randomness, because unpredictability is the entire point. Your Mac already has an excellent source: a hardware random generator feeds the operating system's pool, and that alone is cryptographically sufficient. If we never asked for your mouse, your keys would still be strong.

When you move your mouse, we collect the coordinates and microsecond timings of hundreds of movements and mix them into key generation. The system's randomness and a hash of your movements are combined through a key-derivation function, and the result becomes your keys. By construction the mix can only add unpredictability, so even if your movements were somehow perfectly predictable, the keys would be no weaker than the hardware randomness alone.

Why keep it, then?

We keep it for two reasons. First, the hedge is real, it costs three seconds, and it adds a layer that came from a human hand rather than any silicon we have to trust. Second, and we will admit this openly, the ritual makes a true thing visible. Your keys really are being born in that moment, on that machine, from randomness no one else could reproduce, and watching it happen tells the truth better than a progress bar ever could.