Calculator+

Calculator+ is a full-featured calculator—and behind it lies an end-to-end-encrypted messenger for private one-on-one conversations. Only the calculator is visible on the device. The chats open only when you enter your personal numeric code and press “=.” If you enter any other code, the app simply performs calculations. WHAT THE APP CAN DO • Calculator with basic arithmetic, percentages, sign reversal, and history • Encrypted one-on-one chats: text, images, files, and voice messages • Self-destructing messages with a customizable time limit • Delivery and read receipts—also encrypted • Add contacts via QR code or ID; security number to verify the other party PRIVACY • No phone number, no email, no registration: your ID is your public key • End-to-end encryption (X3DH + Double Ratchet on libsodium) with forward secrecy • The server sees only encrypted data and public keys • All data on the device is encrypted; the key is derived from your code • No ads, no tracking, no analytics services ON-DEVICE PROTECTION • Screenshot and “Recent Apps” lock while the messenger is open • Automatic lock when the app goes to the background and after inactivity • Emergency code: a second code deletes all data immediately and irrevocably—the app then behaves like a normal calculator • Keyboard with no auto-correct; clipboard is automatically cleared PERMISSIONS • Camera: only for scanning contact QR codes • Microphone: only for voice messages • Internet: delivery of encrypted messages IMPORTANT TO KNOW • Your code is the only key to your data. There is intentionally no recovery option—if you forget it, your data is lost. Recommended: at least 8 digits. • Metadata (who messages whom and when) is not hidden from the server. • Self-destructing messages are a convenience feature, not protection against your conversation partner taking a screenshot. • Currently, only one-on-one chats, one device per identity, and no push notifications—new messages arrive as soon as you unlock the messenger.