This app shows how a hybrid cipher works. Don't use it to protect real data. It has known weaknesses, kept on purpose so the algorithm stays easy to follow:

• DES is broken. Its 56-bit key can be found by brute force, so every other block is weak.
• Keys come from System.Random, which isn't a secure random generator.
• The IVs are fixed, so the same text with the same key always gives the same cipher.
• There's no integrity check. A changed cipher file isn't detected; it just decrypts to wrong text or fails.
• The hybrid key is shown as plain text in the window. Anyone who sees or copies it can decrypt the file.

For real data, use a maintained tool built on AES-GCM or ChaCha20-Poly1305, such as 7-Zip's AES-256 archives or age.

A weakness listed above isn't a vulnerability; it's part of the lesson. For anything else, like a way to make the app run code or touch files you didn't pick, please don't open a public issue. Use private vulnerability reporting instead, with the steps to reproduce it and the version you're on.

Fixes go into the latest release only.

• Files: it reads only the file you pick, and writes only where you choose in the save dialog. It keeps no history, settings or logs.
• Keys: a new key is made for each encryption and shown in the window. It's never saved.
• Network: only the update check. It runs a few seconds after the app opens, and again when you click "Check for updates" in About. It sends one request to https://api.github.com/repos/m51v5/HybridCryptographyAlgorithm/releases/latest, which tells GitHub your IP address and the app's version. Nothing you type, encrypt or decrypt is ever sent. It never downloads anything; if a new version is out, it offers to open the release page.
• Links: the About window's links open your browser.