Cryptgeon on Ubuntu 24.04 LTS by cloudimg

Cryptgeon on Ubuntu 24.04 LTS by cloudimg

Cryptgeon is an open source service for sharing a secret once and having it disappear. Paste a password, an API key, a recovery phrase or a file, choose how many times it may be opened or how long it may live, and hand over a single link. The moment the recipient opens it the note is destroyed. This image delivers Cryptgeon fully installed, hardened and serving, so a private alternative to pasting credentials into chat is running within minutes of launch.

The defining property is that your own server cannot read what it stores. Each note is encrypted in the sender's browser with AES in GCM mode using a key generated on that device. That key is placed in the fragment of the share link, after the hash symbol, which browsers never transmit to any server. What arrives at the instance is ciphertext and nothing else. Even with full administrative access to the machine, its memory and its datastore, the contents of a note cannot be recovered. That is a structural guarantee, not a policy promise.

Notes are ephemeral by design. Set a view count and the note is deleted the instant the last permitted view completes; set an expiry instead and the datastore removes it when the timer runs out. Nothing is ever written to disk: the note store runs entirely in memory with snapshotting and append only logging disabled, so no note ciphertext reaches the filesystem, a backup or a captured disk image. Text and file uploads are both supported, with a bounded maximum size so a single upload cannot exhaust the instance.

There are no user accounts, no login and no administrator console, because there is nothing for a directory of users to protect. That deliberate simplicity is why this image concentrates its hardening where the risk actually is. The in memory note store listens only on the loopback interface and is protected by a long random password generated uniquely on each instance at first boot, so no secret is ever baked into the image and no two instances share one. The application and the public web listener are both physically unable to start until that password exists: each is gated on a bootstrap marker written only after the store is locked down, and a pre start check refuses to launch against an unauthenticated datastore.

A hardened reverse proxy fronts the application on the standard web port and is the only thing reachable from outside the instance, with the application and the datastore both bound to loopback. Everything runs as a dedicated unprivileged system user under restricted systemd units, started on boot and restarted on failure. The paired cloudimg deployment guide walks through adding your own TLS certificate, which real use requires because browsers disable the cryptographic functions Cryptgeon depends on over plain connections.

All product and company names are trademarks or registered trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them.

### Highlights

• Cryptgeon 2.9.3, the MIT licensed open source self destructing note and file sharing service, preinstalled and serving behind a hardened reverse proxy, so a private zero knowledge alternative to pasting credentials into chat is running within minutes of launch with no manual setup.
• Your server cannot read what it stores. Every note is encrypted in the sender's browser and the key travels only in the link fragment, which browsers never transmit, so the instance holds ciphertext alone. Notes self destruct after a chosen view count or time limit, and the note store runs entirely in memory with persistence disabled so nothing reaches the disk.
• Security hardened first boot means every instance generates its own long random datastore password before anything opens a port, written to a root only file. The application and the public listener cannot start unauthenticated: a bootstrap marker gates both units and a pre start check refuses a missing, sentinel or weak password. Backed by 24/7 expert technical support from cloudimg.