Nexo
An end-to-end encrypted messenger for Windows. Open source, MIT licensed, no phone number required. Messages use MLS; the feed does not, and Nexo says so.
WindowsOpen sourceMLS encryption
deli.dev
Software, built plainly. From Switzerland.
We ship small, open-source tools and state their limits in plain text. Nexo is our current project.
Based in Switzerland · No trackers · No cookies
01 — Projects
Selected work
One project at a time. Currently shipping Nexo.
02 — Overview
What Nexo does
Private conversations
End-to-end encrypted with MLS (RFC 9420) via OpenMLS. The server stores and forwards ciphertext it cannot read.
A public feed
Posts, images, links, votes and threaded comments, visible to anyone signed in.
Handles, not phone numbers
Accounts are a handle and a password. Nexo never asks for a phone number or an email address.
Local storage is encrypted
History lives in a SQLCipher database whose key is held by Windows for your account alone.
03 — Limits
What Nexo does not protect
Every messenger has limits. Most do not list them.
The feed is not end-to-end encrypted.
Posts and profiles are readable by the server and public to anyone signed in. Content written for strangers cannot also be encrypted to a closed group.
Conversation metadata is visible.
Who talks to whom, when, and message sizes. That is the honest limit of the design.
One device per account.
Signing in elsewhere signs this machine out and wipes its local history.
There is no account recovery.
Forget your password and the account is gone. That is what holding no recovery key means.
04 — Cryptography
How the encryption works
Identity keys are Ed25519.
Each account holds a long-term Ed25519 identity key pair generated on your machine. The private half never leaves it.
A safety number is a fingerprint.
It is computed over both parties' identity keys, so the same sixty digits appear on both machines and nowhere else. Read them aloud or compare them in person.
Key changes are announced.
If a contact's identity key changes, Nexo tells you and marks the conversation until you compare again. A fingerprint you never re-check is not a check.
482109311760482175592083476192357088426109473518266394027185
Sixty digits, twelve groups. Identical on both machines when the keys are the ones you expect.
05 — Install
Download
The installer is not yet code-signed. Windows will show “Windows protected your PC”. Choose More info → Run anyway. We would rather tell you that here than have you meet it unexplained.
Nexo updates itself. Later versions install on their own.
06 — Team
About deli.dev
We are a small development team based in Switzerland. We design, build, and maintain Nexo with a focus on clarity, honest limits, and code that can be inspected.
There is no newsletter, no analytics, and no cookie banner. The site collects nothing.
Get in touch
For questions, collaboration, or a walkthrough of the threat model, reach out on LinkedIn.
Contact on LinkedIn