SecureBit.chat

End-to-end encrypted, peer-to-peer chat that runs entirely in your browser.

No accounts. No servers storing your messages. No installation required.

Features · How it works · Security · Quick start · Documentation

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SecureBit.chat is a browser-based, peer-to-peer messenger built on WebRTC and the Web Crypto API. Two people establish a direct, end-to-end encrypted channel and verify each other in person — there is no registration, no central server relaying or storing messages, and no metadata account to leak. Everything cryptographic happens locally in the two browsers.

It is designed for people who need a small, auditable, zero-infrastructure way to talk privately: journalists and sources, security researchers, or anyone who simply wants a conversation that leaves nothing behind.

Screenshots

Open a secure channel	Encrypted conversation

Features

** Encryption & verification**

• ECDH P-384 key agreement with derived per-session keys, AES-256-GCM payloads, and DTLS-protected transport.
• Double Ratchet forward secrecy — every message is encrypted with its own key, and the session re-keys itself each time the conversation changes direction. See Forward secrecy.
• Interactive Short Authentication String (SAS) verification — you confirm a code out-of-band before the session is trusted, defeating man-in-the-middle attacks.
• Replay protection, message integrity (HMAC), and a live security report you can open at any time during a call.

** Privacy by design**

• Direct peer-to-peer connection — messages never touch a SecureBit server.
• No accounts, no phone numbers, no message history on disk.
• Optional relay-only mode routes traffic through your own TURN server so your IP is never exposed to the peer.
• Local key metadata is stored encrypted in IndexedDB; disconnecting cleans up session state.

** Encrypted calls**

• 1:1 voice and video calls over the same verified peer-to-peer connection — media rides the SAS-verified DTLS-SRTP transport, so calls inherit the session's end-to-end encryption and never traverse a SecureBit server.
• Adaptive audio: Opus with in-band FEC, DTX and RED redundancy for intelligible speech under 15–20% packet loss; audio is prioritised and never throttled by the network controller.
• Adaptive video: VP9/AV1 single-encoding SVC (H.264/VP8 fallback) that degrades by spatial/temporal layer, with a runtime controller that trims video bitrate on loss/RTT and recovers as the link clears.
• Live connection-quality indicator (Excellent → Good → Fair → Weak) shown in the call UI, plus in-call mute and video-upgrade controls.

** Messaging**

• Encrypted voice messages — record in the browser and send over the same end-to-end encrypted transfer channel as files. Audio is captured as PCM/WAV, integrity-protected by a signed hash, and played back inline on the recipient's device without ever touching disk.
• Code blocks with syntax highlighting and an auto-clearing copy button.
• View-once and disappearing messages with countdown timers.
• Unsend (delete for everyone) over the authenticated control channel.
• WhatsApp-style delivery status (sending → sent → delivered) with offline store-and-forward.

Multiple conversations

• Run several independent chats at the same time. Every conversation gets its own encrypted session, keys and verification, so two chats can never mix.
• A side panel lists your open chats with unread badges. Switching is instant, and starting a new chat leaves the others connected.
• Set your availability (Available, Away, Busy or Invisible) and connected peers can see it. You can also give each chat a private label that is stored only on your device and is never sent to the other side.

** File transfer**

• Consent-gated, end-to-end encrypted transfers with resumable, per-chunk progress.
• Strict file-type allowlist; executable and scriptable formats are rejected.

** Progressive Web App**

• Installable on desktop and mobile, works offline, and ships update notifications.

How it works

SecureBit never sees your conversation. A session is built directly between the two browsers:

   Peer A                         Peer B
     │   1. create encrypted offer   │
     │ ────────────────────────────► │   (shared out-of-band: QR / link / paste)
     │                               │
     │   2. return encrypted answer  │
     │ ◄──────────────────────────── │
     │                               │
     │   3. compare SAS code aloud   │
     │  ✓ both confirm  → verified   │
     │                               │
     │ ═══ end-to-end encrypted ════ │

1. Peer A creates an offer (sharable as a QR code, link, or text).
2. Peer B opens it and returns an answer the same way.
3. Both sides see a SAS code and compare it over a trusted channel (in person, a call you recognize, etc.).
4. Only after both peers confirm the matching code does the chat unlock. Three failed attempts terminate the session.

Security model

Layer	Mechanism
Key agreement	ECDH (P-384), per-session derived keys
Forward secrecy	Double Ratchet — per-message keys, DH re-key on each reply
Transport	WebRTC data channel over DTLS
Message encryption	AES-256-GCM, end-to-end
Authentication	Interactive SAS bound to both peers' DTLS fingerprints
Integrity	HMAC + replay protection
Sanitization	DOMPurify text-only rendering boundary
Local storage	Encrypted key metadata in IndexedDB

A session is not treated as verified until both peers complete the SAS flow. This is the step that protects you against a man-in-the-middle: the code must be compared through a channel an attacker cannot impersonate. Until it is completed, the session will not act on control messages from the peer.

Forward secrecy

Message protection does not rest on the keys agreed during the handshake. On top of them SecureBit runs the Double Ratchet — the design used by Signal:

• Every message gets its own key. It is derived from a chain key through a one-way function and discarded as soon as the message is encrypted or read, so keys held now cannot reconstruct earlier ones. Recovering the live state of a session does not expose what was said before.
• Each change of direction re-keys the session. Every reply introduces a fresh ECDH key pair and mixes a new shared secret into the root key, so the conversation continuously moves away from any state an attacker may have captured.
• Out-of-order messages are handled within fixed bounds. Keys are held for messages that have not arrived yet, capped at 512 per chain and 1024 in total and expiring after five minutes, with a limit on how far ahead a message may claim to be.

The ratchet is negotiated during the handshake and used when both peers support it. If one side is on an older release, the session falls back to per-session keys and the security panel reports which of the two is actually in use — it shows the state of your connection, not the capabilities of your client.

Warning

SecureBit.chat is privacy software, not a guarantee. View-once and disappearing messages are cooperative (not screenshot-proof), and a TURN relay can observe both peers' IPs and traffic timing — though never message contents. See SECURITY_DISCLAIMER.md.

Quick start

Run locally

npm install
npm run build
npm run serve

Open the printed local URL in two browser windows or profiles, then:

1. Create an offer in the first window.
2. Transfer it to the second and create an answer.
3. Return the answer to the first window.
4. Compare the SAS code out-of-band and enter it on both sides.
5. Start chatting once both peers are verified.

Install as an app

SecureBit is a PWA — open it in a supported browser and choose Install (or Add to Home Screen on mobile) to run it as a standalone, offline-capable app.

Configuration

TURN / privacy mode

Direct WebRTC connections can reveal IP addresses to the peer. SecureBit supports a relay-only privacy mode:

• Default keeps standard WebRTC behavior with public STUN.
• Relay-only sets iceTransportPolicy: "relay" and requires a configured TURN server.
• STUN alone does not hide IP addresses; public TURN credentials are never bundled.

Configure your own STUN/TURN servers under Advanced network settings, or at deployment time. See doc/CONFIGURATION.md.

File transfer policy

Incoming transfers require explicit consent. Metadata is validated and dangerous names rejected before the prompt appears. Accepted: common raster images, PDF, plain text, and ZIP. Executable/scriptable formats (.exe, .bat, .sh, .js, .msi, .dmg, .jar, .ps1, .vbs, .html, .svg, …) are blocked, and MIME type must agree with the file extension.

Development

Requirements: Node.js 18+ and npm.

npm install
npm test          # run the test suite
npm audit         # check dependencies
npm run build     # build CSS + JS bundles and refresh meta.json
npm run dev       # build and serve locally

Project structure

src/network/      WebRTC connection and session lifecycle
src/transfer/     secure file-transfer implementation
src/crypto/       cryptographic utilities and the Double Ratchet
src/components/   React UI components
src/styles/       component styles
tests/            node:assert suites, run by `npm test`
doc/              technical documentation
dist/             built bundles served in production

Documentation

• SECURITY.md — security policy & reporting
• doc/CONFIGURATION.md — deployment & ICE configuration
• doc/CRYPTOGRAPHY.md — cryptographic design
• doc/SECURITY-ARCHITECTURE.md — architecture overview
• doc/API.md — internal APIs
• CHANGELOG.md — full release history

Contributing & responsible use

Issues and pull requests are welcome. SecureBit.chat is intended for lawful, ethical communication only — please read RESPONSIBLE_USE.md before using or contributing.

License

Released under the MIT License.

_{Built with WebRTC and the Web Crypto API · No servers, no accounts, no compromises.}