mauri870/ransomware ? reverse-engineered prompt

Build me a safe classroom demo app that simulates a ransomware style workflow on dummy files only, so I can show how encryption, key exchange, and recovery work without touching real personal data.

I want a Windows focused tool with three parts, a small server that stores a victim ID and an encryption key, a client that scans a test folder and encrypts matching sample files in the background, and a simple unlocker that restores them with the right key. Use strong modern encryption, make it work on multiple files at once, and keep it fast by streaming file data instead of loading everything into memory.

Please include an easy way to choose a local test folder, a visible note explaining that it is for education only, and a clear recovery flow so I can demonstrate how the unlock step works. If anything about the original setup is unclear, look up current docs online and keep the implementation simple and safe.