Copiosus is just another P2P chat application. Please note: This app does not support Windows 10 S. This software is provided "as is" without warranties or conditions of any kind, either expressed or implied. Please download this app only if: - You care about security. - You don't care about a beautiful UI. - You like to try apps other than WhatsApp and Signal. Lame features: - Send messages. - Send files and images. - Block users. Other features: - End-to-end encryption using an asymmetric key. - Improved end-to-end security using a security key as a second factor which encrypts data using a shared symmetric key. - Minimal privileges required. - No in app purchases. - No ads. How does end-to-end encryption work in this app: 1. Whenever you send a message M a random symmetric key R is generated 2. R is encrypted using the asymmetric (public) key of the other user resulting in A 3. M is encrypted with R resulting in N 4. If security key S is set: N is encrypted by S 5. N and A is sent to the destination