🔐 Secure File Transfer in Shell (SFTP-Shell)

A secure file transfer system written in pure Bash that leverages industry-standard encryption tools (OpenSSL & GPG) to ensure files are safely shared over insecure networks using SCP or RSYNC over SSH.

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🎯 Project Goal

This project aims to provide a minimal, secure, and easy-to-use command-line tool to:

• Encrypt sensitive files locally before sending them.
• Transfer files securely using existing encrypted channels (SCP/RSYNC via SSH).
• Allow decryption only by authorized users (via password or public key).
• Be lightweight and run on most UNIX-based systems without dependencies on heavy software.

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Team Members

• Mohamed Wael
• Eslaam Ibrahim
• Malak Ali

🔒 Security Approach

Technique	Tool Used	Notes
Symmetric Encryption	OpenSSL (AES-256-CBC)	User-provided password; fast and simple.
Asymmetric Encryption	GPG	Secure key-based encryption; no password sharing.
Transfer Layer	SCP / RSYNC	Uses SSH; encrypted and authenticated.

All encryption happens locally, so no plain data is sent over the network. Passwords are not stored, only used in memory temporarily.

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📦 Features

• 📁 Upload or download mode
• 🔐 Two encryption options:
  • AES-256 (OpenSSL)
  • GPG (PGP standard)
• 📤 Transfer via:
  • scp (simple & secure)
  • rsync (efficient for large or repeated transfers)
• ✅ Error checking at each step
• 🧠 Modular functions for easy customization
• 🧪 Temporary password handling using mktemp

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📚 Use Cases

• ✅ System admins sending sensitive configuration files.
• ✅ Developers deploying encrypted backups.
• ✅ Students learning about secure file sharing and Bash scripting.
• ✅ Transferring academic or medical documents securely.

⚙️ How It Works (Internal Flow)

Step 1: User chooses upload or download
Step 2: User selects encryption method (AES or GPG)
Step 3: Script encrypts (upload) or decrypts (download) the file
Step 4: File is transferred via SCP or RSYNC
Step 5: User is notified of success/failure

🧰 Requirements

Make sure you have these tools installed:

• bash
• openssl
• gpg
• scp
• rsync
• ssh

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Install using:

sudo apt install openssh-client rsync openssl gnupg

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🚀 Getting Started

1. Clone the repository

git clone https://github.com/your-username/secure-file-transfer-shell.git
cd secure-file-transfer-shell

2. Make the script executable

chmod +x SFTP.sh

3. Run the script

./SFTP.sh

Follow the menu instructions interactively.

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🧪 Example: Uploading with AES

./SFTP.sh

Follow prompts:

• Choose option 1 (Upload)
• Choose AES encryption
• Enter file name
• Choose transfer method
• Enter destination (e.g. user@host:/path)

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🛡️ GPG Encryption Guide

To use asymmetric encryption with GPG, follow these steps:

Generate your key:

gpg --full-generate-key

Share your public key:

gpg --armor --export you@example.com

Import a recipient key:

gpg --import recipient-key.asc

🤝 Contributions

Feel free to fork this repo, suggest features, or submit pull requests!