The latest articles on DEV Community by SiddhaDo (@_a95a94c485cb1604c1de0c). https://dev.to/_a95a94c485cb1604c1de0c https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F2740555%2F18210838-4f34-4a7e-91bb-4421dc24de2b.jpg https://dev.to/_a95a94c485cb1604c1de0c en SiddhaDo Sun, 13 Jul 2025 09:46:58 +0000 https://dev.to/_a95a94c485cb1604c1de0c/bitchat-offline-bluetooth-mesh-messaging-without-sim-wi-fi-or-servers-4d2l https://dev.to/_a95a94c485cb1604c1de0c/bitchat-offline-bluetooth-mesh-messaging-without-sim-wi-fi-or-servers-4d2l <blockquote> <p>What if your phone could send secure end-to-end encrypted messages without Wi-Fi, mobile data, or even SIM card?</p> </blockquote> <p>Welcome to <a href="https://www.bit-chat.xyz/" rel="noopener noreferrer"><strong>BitChat</strong></a> — a lightweight Bluetooth mesh chat app that works <strong>entirely offline</strong>, hopping from device to device using <strong>Bluetooth Low Energy</strong>.</p> <h2> 🔌 What Is BitChat? </h2> <p>BitChat is an open-source messaging app that:</p> <ul> <li>Uses <strong>Bluetooth LE</strong> mesh for offline routing (up to 300 m per hop)</li> <li>Encrypts everything with <strong>ChaCha20-Poly1305</strong> </li> <li>Stores nothing on a central server (not even login)</li> <li>Works on <strong>iOS, Android and macOS</strong> </li> <li>Runs even when cellular service is down</li> </ul> <p>👉 <strong><a href="https://www.bit-chat.xyz/bitchat.apk" rel="noopener noreferrer">Try Android here</a></strong> — no sign-up required.</p> <h2> 📡 Why Mesh Matters </h2> <p>Unlike Signal or WhatsApp, BitChat can send messages <strong>peer-to-peer</strong>.<br><br> In fact, messages can <strong>hop</strong> between multiple phones, enabling offline comms in:</p> <ul> <li>🏞 Remote regions without coverage </li> <li>🛬 Airports, trains, undergrounds </li> <li>🌪️ Emergencies when the Internet is out </li> <li>🛑 Areas under censorship or surveillance</li> </ul> <p>We tested <a href="https://www.bit-chat.xyz/field-test/" rel="noopener noreferrer">multi-hop routing across 3 phones</a> — the result? 210 meters of offline encrypted chat.</p> <h2> 🔒 Tech Stack at a Glance </h2> <div class="table-wrapper-paragraph"><table> <thead> <tr> <th>Component</th> <th>Tech</th> </tr> </thead> <tbody> <tr> <td>Transport</td> <td>Bluetooth LE (CoreBluetooth / Android BLE)</td> </tr> <tr> <td>Encryption</td> <td>X25519 for key exchange, ChaCha20-Poly1305 for messages</td> </tr> <tr> <td>Mesh Routing</td> <td>Store-and-forward with TTL &amp; random delays</td> </tr> <tr> <td>App Size</td> <td>~6 MB (no SDK bloat)</td> </tr> <tr> <td>Privacy Model</td> <td>No phone number, account, or metadata</td> </tr> </tbody> </table></div> <p>You can <strong>see the routing demo videos</strong> and test metrics here 👉 <a href="https://www.bit-chat.xyz/field-test/" rel="noopener noreferrer">https://www.bit-chat.xyz/field-test/</a></p> <h2> 📲 Download &amp; Try It </h2> <div class="table-wrapper-paragraph"><table> <thead> <tr> <th>Platform</th> <th>Link</th> </tr> </thead> <tbody> <tr> <td>iOS</td> <td><a href="https://www.bit-chat.xyz/#ios-testflight" rel="noopener noreferrer">Join TestFlight (Beta)</a></td> </tr> <tr> <td>Android</td> <td><a href="https://www.bit-chat.xyz/bitchat.apk" rel="noopener noreferrer">Download APK</a></td> </tr> <tr> <td>macOS</td> <td><code>brew install xcodegen &amp;&amp; git clone</code></td> </tr> </tbody> </table></div> <p>BitChat is fully open-source — feel free to fork and contribute.</p> <h2> 💬 Final Thoughts </h2> <p>We don't think BitChat replaces Signal or Matrix — but it <strong>complements</strong> them.<br><br> When everything else breaks, you still want <em>some way</em> to stay in touch — even if that’s via mesh-hopped BLE packets.</p> <blockquote> <p>Got feedback or want to contribute? Drop us a line via <a href="https://www.bit-chat.xyz" rel="noopener noreferrer">https://www.bit-chat.xyz</a> — or fork the project and start hacking.<br><br> Let’s decentralise the last mile, one Bluetooth hop at a time. 🔗</p> </blockquote> bluetooth meshnetwork privacy opensource