The app-lock PIN closes Kissend on a shared phone. A hidden list and a per-chat PIN cover one thread. Quiet hours hold notifications, and mute stops a banner for 8 hours, a week, or until you turn it off.
Those PINs are stored as hashes. They close the screen for a person who can already see the phone.
Across devices
Messages are delivered through Kissend so the other person can receive them, including after you switch devices. The privacy policy describes how those messages are stored.
Screenshot detection is not shipped. View-once and disappearing messages shorten how long a picture stays in the thread. They cannot stop another person from photographing the screen.