I made it working: 1. Clone the Signal-Desktop Repo 2. Edit the File: "js/background.js" Line 56 SERVER_URL to 'https://textsecure-service.whispersystems.org' and Line 57 ATTACHMENT_SERVER_URL to 'https://whispersystems-textsecure-attachments.s3.amazonaws.c... and save it 3. Open chrome://extensions/ 4. Activate Developer mode 5. Click "Load unpacked extension..." and select the Signal-Desktop directory 6. Open https://textsecure-service.whispersystems.org/ and accept the cert (otherwise you won't see the qr code) 7. Scan the qr code and have fun!