🔐 SecureFile – File Encryption & Decryption Tool

SecureFile is a web-based cybersecurity application that allows users to securely encrypt and decrypt files using modern cryptographic techniques.

The application uses AES-256-GCM encryption and PBKDF2-HMAC-SHA256 for secure password-based key derivation.

Users can encrypt a file with a password, download the encrypted file, and later decrypt it using the same password.

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🚀 Features

🔒 File Encryption

• Upload any supported file.
• Enter a password.
• Encrypt the file using AES-256-GCM.
• Download the encrypted file.
• The original file remains unchanged.

🔓 File Decryption

• Upload an encrypted .enc file.
• Enter the original password.
• Decrypt the file.
• Download the original file.

🛡️ Security

• AES-256-GCM authenticated encryption.
• PBKDF2-HMAC-SHA256 for password-based key derivation.
• Random salt for every encryption operation.
• Random IV/nonce for every encryption operation.
• Passwords are never stored.
• Uploaded files are not permanently stored.
• Modified or corrupted encrypted files are rejected.

🚫 Encrypted File Protection

SecureFile prevents users from encrypting an already encrypted SecureFile file.

document.pdf
      ↓
   Encrypt
      ↓
document.pdf.enc

Trying to encrypt the .enc file again will result in:

❌ File is already encrypted

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🧠 How It Works

Encryption

Original File
     ↓
User Password
     ↓
PBKDF2-HMAC-SHA256
     ↓
Encryption Key
     ↓
AES-256-GCM
     ↓
Encrypted File (.enc)

Decryption

Encrypted File (.enc)
     ↓
User Password
     ↓
PBKDF2-HMAC-SHA256
     ↓
Encryption Key
     ↓
AES-256-GCM
     ↓
Original File

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🔐 Why AES-256-GCM?

AES (Advanced Encryption Standard) is a widely used symmetric encryption algorithm.

SecureFile uses AES-256-GCM because it provides:

• Strong encryption
• Confidentiality
• Integrity protection
• Authentication of encrypted data

GCM also helps detect if an encrypted file has been modified or corrupted.

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🔑 Password Security

The user's password is not directly used as the AES encryption key.

Instead:

Password
   +
Random Salt
   ↓
PBKDF2-HMAC-SHA256
   ↓
256-bit Encryption Key

This makes password-based encryption significantly stronger than directly using the password as an encryption key.

The password is never stored by the application.

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📁 Encrypted File Format

SecureFile stores the required cryptographic information inside the encrypted file.

Conceptually:

┌──────────────────────┐
│ SecureFile Header    │
├──────────────────────┤
│ Version              │
├──────────────────────┤
│ Random Salt          │
├──────────────────────┤
│ Random IV / Nonce    │
├──────────────────────┤
│ Encrypted File Data  │
├──────────────────────┤
│ Authentication Tag   │
└──────────────────────┘

The password is not stored inside the file.

Without the correct password, the encrypted file cannot be successfully decrypted.

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🖥️ User Workflow

Encrypt a File

1. Open SecureFile.
2. Select Encrypt.
3. Choose a file.
4. Enter a password.
5. Click Encrypt File.
6. Download the .enc file.

Decrypt a File

1. Select Decrypt.
2. Choose the encrypted .enc file.
3. Enter the same password used during encryption.
4. Click Decrypt File.
5. Download the restored file.

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🚫 Invalid Operations

SecureFile prevents common invalid operations.

Encrypting an already encrypted file

document.pdf.enc
       ↓
     Encrypt
       ↓
❌ Already encrypted

Using the wrong password

Encrypted File
      ↓
Wrong Password
      ↓
❌ Decryption Failed

Modified encrypted file

If the encrypted file is modified after encryption:

Encrypted File
      ↓
Modified / Corrupted
      ↓
AES-GCM Verification
      ↓
❌ Integrity Check Failed

---

🛠️ Technologies Used

Backend

• Java
• Spring Boot
• Spring Web
• Java Cryptography Architecture (JCA)

Cryptography

• AES-256-GCM
• PBKDF2-HMAC-SHA256
• SecureRandom

Frontend

• HTML5
• CSS3
• JavaScript

Deployment

• Docker
• GitHub
• Cloud deployment

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📂 Project Structure

SecureFile/
│
├── src/
│   └── main/
│       ├── java/
│       │   └── com/
│       │       └── securefile/
│       │           ├── controller/
│       │           ├── service/
│       │           ├── security/
│       │           ├── config/
│       │           └── SecureFileApplication.java
│       │
│       └── resources/
│           ├── static/
│           │   ├── index.html
│           │   ├── css/
│           │   └── js/
│           │
│           └── application.properties
│
├── Dockerfile
├── .gitignore
├── pom.xml
└── README.md

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⚙️ Running Locally

Prerequisites

Make sure you have:

• Java 17 or later
• Maven
• Git

Clone the repository

git clone <YOUR-GITHUB-REPOSITORY>

Navigate into the project

cd SecureFile

Run the application

mvn spring-boot:run

The application will start locally.

Open:

http://localhost:8080

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🐳 Running with Docker

Build the Docker image:

docker build -t securefile .

Run the container:

docker run -p 8080:8080 securefile

Then open:

http://localhost:8080

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🌐 Public Deployment

SecureFile can be deployed as a public web application.

Recommended architecture:

GitHub
   ↓
Docker
   ↓
Cloud Platform
   ↓
Public URL
   ↓
Anyone can access SecureFile

No account or login is required.

Users only need a web browser.

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🔒 Security Considerations

SecureFile is designed as an educational cybersecurity project and follows important security principles:

• Strong authenticated encryption
• Random cryptographic salt
• Random IV/nonce
• Password-based key derivation
• No password storage
• No permanent file storage
• File validation
• Protection against repeated encryption
• Integrity verification using AES-GCM
• Safe error handling
• No sensitive information in error responses

Important

The security of the encrypted file ultimately depends on the strength of the password chosen by the user.

Users should use strong, unique passwords.

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🎯 Project Objectives

The main objectives of SecureFile are:

1. Demonstrate practical use of cryptography.
2. Understand symmetric encryption.
3. Learn how AES works in real applications.
4. Understand password-based key derivation.
5. Demonstrate file confidentiality.
6. Demonstrate file integrity verification.
7. Build a practical cybersecurity application.
8. Provide a simple interface that non-technical users can understand.

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🎓 Academic Use

SecureFile can be used as a college cybersecurity project to demonstrate concepts such as:

• Cryptography
• Symmetric encryption
• AES
• Password-based encryption
• Key derivation
• Authentication
• Data confidentiality
• Data integrity
• Secure file handling

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🔮 Future Enhancements

Possible future improvements include:

• Multiple file encryption
• Folder encryption
• Password strength meter
• Secure file sharing
• Expiring download links
• Client-side encryption
• Cloud storage integration
• User accounts
• File integrity verification
• Encryption history
• QR-based secure file sharing

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👨‍💻 Author

Godson Suresh

Cybersecurity / Computer Science Project

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📜 License

This project is intended primarily for educational and academic purposes.

Add an appropriate open-source license if you plan to distribute the project publicly.