About

What it is

A public wall of sealed letters that open by themselves at a moment in the future. Anyone can write one, to anyone, and choose the day. Until that day, nobody can read it. Not the person it is for, not this server, not the people who run it. After that day, anyone can, and the letter stays on the wall as part of a public memory. Private letters exist too; those live only behind their link.

How the lock works

The lock is not a password and not a secret kept somewhere. The lock is time. Your browser encrypts the letter against a future round of the drand beacon, a public source of randomness run jointly by a group of independent organisations called the League of Entropy. Every three seconds the network publishes a new signed value; the key that opens your letter is the signature of the round that falls on your chosen moment. That signature does not exist yet. It cannot be computed early by anyone, and once published it is public for everyone. This is called timelock encryption; the construction is described in the tlock paper. We only ever store the encrypted letter, and every seal is appended to a public hash chain you can check yourself.

Who builds it

Later. is made and hosted in Belgium by GoTrust BV. Data stays on a server in Europe. There is no tracking and there are no cookies beyond what the page needs to work. Questions: jeroen@gotrust.be.