Hush 1.1.3

Private messaging with post-quantum end-to-end encryption, for Windows and Android.

Messages

• One-to-one conversations, text and images.
• Formatting: *bold*, _italic_, ~strikethrough~, `monospace`, fenced blocks and line breaks.
• Emoji picker that remembers the ones you use.
• Delivery state on your own messages: sent, delivered, read.
• Delete a message for yourself or for everyone, select several at once, or wipe a whole conversation.
• Desktop notifications; on a phone, a choice of sound, vibration or nothing.

Contacts

• Added by username, and only after both sides accept.
• Presence — online, away, busy — and last seen, shown only to accepted contacts.
• Profile pictures, sent to each contact inside an encrypted message. The server never sees one.
• Block and unblock.

Encryption

• PQXDH key agreement (X25519 + Kyber-1024) and Double Ratchet, through libsignal. Resistant to an attacker who records today and decrypts once quantum computers exist.
• The server relays opaque blobs. It cannot read a message, and it stores no history: a message is deleted the moment it is delivered.
• Each contact's identity key is pinned. If it ever changes, nothing is sent to them and nothing of theirs is read until you confirm it was really them, with both fingerprints side by side to read out over some other channel.
• What is stored on the device — messages, contact names, the identity key, the session token — is sealed with XChaCha20-Poly1305 under a key the operating system wraps, so the files alone are useless on another machine.

Your account

• One device at a time. Signing in somewhere else ends the previous session on the spot.
• Sign out ends the session on the server too, so the old one cannot be resumed.
• Conversations move between devices through a file you export, protected by a password of your choosing (Argon2id + XChaCha20-Poly1305).
• Email verification on sign-up, and password reset by email.

The app

• Windows and Android, sharing the same Rust core.
• Spanish and English, light and dark, adjustable text size.
• Closes to the system tray, so messages keep arriving.
• Updates itself in the background from the server, checking a signature that only the developer can produce.

Downloads

• Windows: Hush_1.1.3_x64-setup.exe
• Android: Hush_1.1.3_arm64.apk (installed by hand; it is not on any store)