00 Application · uChat

Chat.
Encrypted by default.

Messaging and conversations

01 What you can do

What you can do

What you can do with uChat.

01

One-to-one and group conversations

End-to-end encrypted messaging for any size of conversation. Text, voice messages with playback controls, replies, emoji picker, bookmarks. Conversations persist across devices and synchronize live as peers type.

Use case

Chat fits naturally into this flow.

02

File and photo attachments

Drag-and-drop photos, documents, anything. Each attachment is encrypted client-side before it leaves your device, then synced to every participant in the conversation.

Use case

Chat fits naturally into this flow.

03

In-thread auto-translate and task creation

Translate messages in-thread to your preferred language. Convert any message into a task with one tap. AI features run against your AI provider, on your keys.

Use case

Chat fits naturally into this flow.

02 Security

Security

Security for uChat.

Every UltimaOS app shares the same post-quantum cryptographic stack, so the security properties below apply uniformly. App-specific considerations are noted where they apply.

01

Post-quantum cryptography by default

All authentication and key exchange uses NIST-standardized ML-DSA-65 (FIPS 204) signatures and ML-KEM-768 (FIPS 203) key encapsulation. There is zero RSA, zero elliptic-curve, zero classical-only crypto in the authentication path. Defeats store-now-decrypt-later attacks.

02

End-to-end encryption on your device

Every payload is encrypted in your browser using XChaCha20-Poly1305 (RFC 8439) with a 192-bit nonce and a Poly1305 authentication tag. The plaintext exists only in your tab's memory. When you close the tab, the plaintext is gone.

03

Zero-knowledge server

The UltimaOS server only ever stores ciphertext and public keys. We cannot read your data — by design, not by promise. There is no encryption backdoor, no master key, no key escrow.

04

Multi-device sync, single private key

Your private key is derived from your passphrase using Argon2id with high parameters. New devices derive the same key locally and can decrypt your entire history. The passphrase is never sent to the server — it is verified by an ML-DSA-65 signature on a server-issued challenge.

03 How it works

How it works

How uChat works.

  1. 01

    Open uChat in your browser

    UltimaOS runs in any modern browser — Chrome, Firefox, Safari, Edge. Nothing to install. Sign in with your passphrase-derived key, or restore from a 3-of-5 social recovery if you are on a new device.

  2. 02

    Your data is encrypted before it leaves your device

    Every action — sending a message, uploading a file, creating a task, scheduling an event — is encrypted with XChaCha20-Poly1305 and authenticated with an ML-DSA-65 signature before any byte crosses the network boundary.

  3. 03

    Server stores ciphertext, returns it on demand

    The UltimaOS server keeps an opaque blob per account and per conversation. When you open uChat, the encrypted blobs are streamed to your device, decrypted locally, and rendered. The server never sees plaintext.

  4. 04

    Changes sync to every device you sign in on

    Any change you make is encrypted and uploaded; every other device you are signed in on pulls the new ciphertext and decrypts it. Live multi-device sync, with the cryptography guarantee that only your devices can read it.

04 Inside the suite

Inside the suite

How uChat fits in the suite.

01

Contacts

Start encrypted conversations from your address book. Type-ahead suggestions are powered by Contacts and stay encrypted.

02

Files

Drag-and-drop photos, documents and anything else. Files encrypts and syncs them across the conversation.

03

Tasks

Convert any message into a task with one tap. Tasks inherits the message's encryption and provenance.

04

Calendar

Schedule a meeting from a thread. Calendar events link back to the conversation they came from.

05 Get started

Get started

Get started with uChat.

  1. 01

    Open uChat in your browser

    UltimaOS runs in Chrome, Firefox, Safari and Edge. Nothing to install. Sign in with your passphrase to derive your private key locally.

  2. 02

    Open the workspace and launch uChat

    The launcher shows every app. uChat is right there with its capsule video preview. Click to open.

  3. 03

    Connect it with the rest of the suite

    uChat works alone, but it shines when combined with the rest of the UltimaOS apps. Same private key, same encryption, one workspace.

07 Frequently asked

Common questions

Questions about uChat.

Is uChat end-to-end encrypted?
Short answer

Yes. All content in uChat is encrypted in your browser using XChaCha20-Poly1305 with a fresh key per item. The UltimaOS server only ever stores ciphertext and public keys — it cannot decrypt your data, no matter who asks.

What cryptography does uChat use?
Short answer

uChat uses the same post-quantum stack as every other UltimaOS app: ML-DSA-65 (FIPS 204) for authentication, ML-KEM-768 (FIPS 203) for key encapsulation, XChaCha20-Poly1305 (RFC 8439) for symmetric encryption, HKDF-SHA256 for key derivation, and Argon2id for passphrase hashing.

Can I use uChat on multiple devices?
Short answer

Yes. Sign in on any device with your passphrase and the same private key is derived locally. All your uChat content is then decrypted from the encrypted blobs the server returns. Changes sync live across all signed-in devices.

Is uChat GDPR-compliant?
Short answer

Yes. UltimaOS is built and operated in the European Union by an EU company. The architecture is GDPR-compliant by design — encrypted data, EU-only infrastructure, no US CLOUD Act exposure, no advertising, no third-party trackers. See the GDPR page for the full breakdown.

How much does uChat cost?
Short answer

During early access, UltimaOS is free for individuals and organizations. After early access, pricing will be per-seat with accessible family tiers and per-organization plans for businesses. There is no per-app add-on.

Can I export my uChat data?
Short answer

Yes. UltimaOS supports encrypted export of all your content for backup and portability. The export is encrypted to a key you control; you can store it on your own infrastructure or in a personal encrypted backup.

Can I send disappearing messages in uChat?
Short answer

Messages in uChat are encrypted at rest with no server-side retention. You can set per-conversation retention rules: messages auto-purge after a chosen time. Once purged, the ciphertext is deleted from the server and unrecoverable.

Does uChat support voice and video calls?
Short answer

One-to-one voice and video calls live in uMeet, launched from a uChat conversation. uChat itself focuses on text, voice messages with playback controls, file attachments and replies.