Many users care deeply about whether Keychat will eventually support a true multi-device experience, where the same ID can be used seamlessly across several devices.

Keychat relies on ratchet algorithms from the Signal and MLS protocols, deriving a fresh encryption key for every single message and discarding it after use. This makes the system inherently stateful—the cryptographic state on each device is constantly evolving—and it ensures that both past and future messages remain protected even if a device’s encryption state is later compromised. This property is known as forward secrecy and backward secrecy (also called post-compromise security).

For exactly this reason, Keychat cannot behave like Nostr DMs (NIP-4, NIP-17), which reuse a static encryption key and therefore lack forward and backward secrecy, or like Telegram, which by default does not use end-to-end encryption, and simply allow the same ID to be logged in and used actively on multiple devices at the same time.

When we think about multi-device support in Keychat, we can start from a baseline design. Suppose Alice and Bob each have a smartphone and a computer with Keychat installed. When they chat, those four devices can conceptually form a four-device group, where each pair of devices maintains its own secure session.

From there, we still need a more refined design that improves this experience and avoids relying on centralized servers.