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From time to time, we need to transmit sensitive information that we want only the sender and the receiver to know the content. It could be your accounting documents, some sensitive client data, etc. We believe that not even the service provider should be able to decrypt the files.
Because people are often reluctant to adopt new procedures and to use new tools, this guide is based on none technical solution, simple enough for adoption, and free. It assumes the all parties have a smart phone, although files are transmitted from the desktop computer. This solution uses two tools from well-known companies that I feel I can trust:
What you need:
- A Smart phone (iOS or Android).
- Chrome Web browser on your desktop.
- Install Google Chrome on your computer.
- Install Signal by Open Whisper Systems on your smartphone:
- Install Signal Desktop on Chrome.
- Register your desktop computer using your smart phone.
- Open Mozilla Send service.
- Drag and drop the file to send.
- Maximum size is 1GB.
- It is encrypted on your device. Not even Mozilla can decrypt it.
- Copy the link.
- It expires after either 24h, or the first download.
- This is the only key to the file. Never send it in clear text, this is why you need Signal Desktop.
- Open Signal Desktop from Chrome.
- Select your contact.
- Write a message and paste the link.
- Send your message!
Bravo, you have just sent an end-to-end encrypted message and file. The receiver should also use Signal Desktop to download the file on her own desktop computer.
