HeartbeatLetter allows users to create "letters" and designate a recipient. Users set up a periodic check-in cycle (every x days). If they do not confirm safety within that time, the system will automatically activate and send the created letters to the recipient.

Users can choose:

• Regular letter: sent directly to the recipient's email.
• End-to-end encrypted letter (client-side encryption): the content is encrypted right on the user's device. The backend only stores the encrypted data.
  When activated, the recipient will receive an email containing a link to the portal and needs to enter a key (along with a hint provided by the sender) to decrypt the content.

HeartbeatLetter ensures:

• No one can read the letter before the activation time.
• Even the system cannot access the content of the encrypted letter.
• Users have full control over their data and security.

A simple yet powerful solution to protect important messages when the worst happens.