This is the structure of the main repo

Create the main directory

New-Item -ItemType Directory -Name "project-root"

Create subdirectories

New-Item -ItemType Directory -Path "project-root/src/html"
New-Item -ItemType Directory -Path "project-root/src/css"
New-Item -ItemType Directory -Path "project-root/src/js"
New-Item -ItemType Directory -Path "project-root/lib"
New-Item -ItemType Directory -Path "project-root/bin"
New-Item -ItemType Directory -Path "project-root/assets/images"
New-Item -ItemType Directory -Path "project-root/tests"

Tree structure of the project

/project-root
│
├── /bin                   # Scripts or executables (optional)
│
├── /lib                   # Libraries or third-party code (optional)
│   └── /vendor            # External libraries (e.g., jQuery, Bootstrap)
│
├── /src                   # Source files
│   ├── /css               # CSS stylesheets
│   │   └── styles.css     # Main stylesheet
│   │
│   ├── /js                # JavaScript files
│   │   └── script.js      # Main script
│   │
│   └── /html              # HTML files
│       └── index.html     # Main HTML file
│
├── /assets                # Images, fonts, etc.
│   └── /images            # Images folder
│
├── /tests                 # Automated tests (optional)
│
├── README.md              # Project description
│
├── package.json           # (Optional if using npm for package management)
│
└── .gitignore             # Git ignore file

Project Implementation Summary

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Technologies and Languages

After discussing whether to use ViteJS with TypeScript or JavaScript with HTML, we settled on:

• JavaScript: For client-side logic.
• HTML & DOM Manipulation: Used for UI components such as file upload, dropdown menus, and displaying decrypted files.
• Local Storage: Used to store the encryption key and encrypted file data in a persistent manner.
• Web Crypto API: Provides secure cryptographic functions for encryption, decryption, and hashing.

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File Encryption and Decryption Workflow

• AES-GCM (Advanced Encryption Standard - Galois/Counter Mode): Chosen after research for its efficiency and authenticated encryption properties. AES-GCM helps achieve confidentiality by encrypting file data with a secure key.
• IV (Initialization Vector): Research highlighted that data breaches often occur due to patterns in encrypted data. Using an IV introduces randomness, preventing patterns in the ciphertext.

Implementation:

• Generate or retrieve a 256-bit AES-GCM encryption key, which is stored as JSON in Local Storage.
• Convert the file to an ArrayBuffer, encrypt it with the key, and store the result (encrypted data and IV) in Local Storage and memory cache.

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Key Management

• Local Storage: Used to store the encryption key, allowing it to be retrieved on the same machine at any time.
• Key Persistence: On the first run, the application generates a new key and saves it in Local Storage. For future uses, the same key is retrieved, ensuring consistency and sustainability.

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Data Integrity Mechanism

We used SHA-256 Hashing to create a hash of the file data before encryption. This hash is then used later to verify the file’s integrity upon decryption by comparing it with a hash of the decrypted data, thereby achieving integrity.

Team Rationale:

• SHA-256 guarantees data integrity by detecting any accidental or intentional alterations in the file contents.

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File Storage and Retrieval

• File Storage in Cache: Local Storage is used for fast and easy storage and retrieval.
• Decryption Process: On decryption, the application retrieves the encrypted data, decrypts it with the stored key, verifies integrity using the SHA-256 hash, and displays the file only if integrity is confirmed.

File Display Formatting:

• After decryption, files are displayed using Blob, URLs, and DOM elements like img, iframe, or download links.

---

Cryptographic Mechanisms - Rationale

• AES-GCM: Selected for secure and authenticated encryption. This symmetric encryption method (using one key for both encryption and decryption) is efficient, fast, and allows more storage, making it well-suited for Local Storage use.
• SHA-256: Ensures data integrity, preventing accidental or intentional corruption.
• IV (Initialization Vector): Prevents repeated data patterns and makes ciphertexts unique for each encryption, even when the same data is encrypted multiple times.

---

Conclusion

To achieve the CIA principles (Confidentiality, Integrity, Availability), we followed this approach:

• AES-GCM: Achieves confidentiality.
• SHA-256: Achieves integrity.

When both are successfully achieved, the file becomes available in Local Storage.