📁 Secure File Sharing in

k4li-chat-cli to support encrypted file sharing while preserving end-to-end encryption.

🔐 How it Works

The system uses ntfy's built-in support for attachments combined with symmetric AES encryption between peers.

1. The file is encrypted with a shared key.
2. The encrypted file is uploaded as an ntfy attachment.
3. A message is sent with the download URL (optionally encrypted).
4. Peers can download and decrypt the file locally.

🛠 CLI Usage Example

Sending a File

/sendfile path/to/document.pdf

• Encrypts the file with AES (shared secret with peer)

Receiving and Decrypting

• Downloads the encrypted file
• Decrypts it using the shared AES key
• Saves it as the original filename

🔒 Security Notes

• Files are encrypted client-side using the same AES-256 key used for messages.
• The ntfy server only stores ciphertext, with no knowledge of the contents.
• Metadata (like the original filename) is encrypted as well.

✅ Ideal For

• Sharing notes, photos, PDFs between trusted peers
• Secure collaboration while traveling or on untrusted networks
• Anonymous dropboxes (when combined with anonymous usernames)