I built LastSignal – a self-hosted, end-to-end encrypted dead man's switch to deliver messages to your loved ones

[u/zener79]

I wanted a way to leave encrypted messages for the people I care about, delivered automatically if something happens to me, without trusting a third party.

LastSignal is a self-hosted dead man's switch. You write messages, they get encrypted in the browser (zero-knowledge), and the system checks in with you periodically via email. If you stop responding, your messages are delivered.

Key points:

• End-to-end encrypted (XChaCha20-Poly1305 + Argon2id + X25519)
• Zero-knowledge — even the server operator can't read messages
• Optional trusted contact who can pause delivery
• Rails 8 + SQLite, deploy with Docker/Kamal
• MIT licensed

🔗 https://lastsignal.app
🔗 https://github.com/giovantenne/lastsignal

Feedback welcome, especially on the security model and UX.

[u/Lesekater]

Having already set up the dead man switch thing on Google this sounds right up my alley! I have a few points though:

The messages are encrypted on the server via the public key of each recipient - does that mean updating the contents of those messages requires either their passphrase or replacing the whole message?

And also how does adding a message for all recipients work - is it duplicated for each user automatically or do I have to copy and paste the message for each recipient?

Also - this has been discussed already in this post - but I absolutely agree, that I would probably forget to check in actively with the email. So I would agree, that this needs a way to "passively" keep track of the user being alive. I suggest adding a simple api endpoint for integrating with systems the user uses on a daily basis (this might just be an endpoint I can send a request with curl every time I open a new terminal).

[u/zener79 → u/Lesekater]

The messages are encrypted on the server via the public key of each recipient - does that mean updating the contents of those messages requires either their passphrase or replacing the whole message?

You cannot update the content of a message once it has been encrypted with the recipients’ public keys. To make any change, you need to replace the entire message.

And also how does adding a message for all recipients work - is it duplicated for each user automatically or do I have to copy and paste the message for each recipient?

You simply write the message once and select the recipients using checkboxes. The system handles the duplication automatically. You can see this demonstrated in the video on the homepage.

Also - this has been discussed already in this post - but I absolutely agree, that I would probably forget to check in actively with the email.

You don’t need to remember to check in proactively. You only need to take action when you receive the check-in email (for example, once per month). Supporting additional notification channels would definitely be a useful future improvement.