Safefile | Secure File Encryptor (Browser-Based)

A simple, secure, and fully offline file encryption tool built with vanilla JavaScript, using modern browser cryptography standards.
No dependencies. No server. No data ever leaves your device. Styled with modest-ui.

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Features

• AES-256-GCM encryption for confidentiality and integrity
• PBKDF2 with SHA-256 and 100,000 iterations for strong password-based key derivation
• All operations happen locally in your browser
• Mobile-friendly, responsive UI
• Styled with modest-ui — a minimal, themeable CSS component library
• No build tools, no frameworks — just open index.html and go

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How It Works

1. Choose a file you want to encrypt or decrypt
2. Enter a secure password
3. Click Encrypt or Decrypt
4. The tool:
   • Derives a secure key from your password using PBKDF2 + SHA-256
   • Encrypts/decrypts your file using AES-256-GCM
   • Combines metadata (salt + IV) with the ciphertext
5. Automatically prompts a secure download of the output file

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Why It's Safe

• Uses the Web Crypto API, built into all modern browsers
• All encryption/decryption is done in-memory
• AES-GCM provides both encryption and tamper protection
• PBKDF2 with 100,000 iterations defends against brute-force attacks

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File Format

The encrypted file is structured as follows:

Bytes	Contents
0–15	Salt (16 bytes)
16–27	IV (Initialization Vector, 12 bytes)
28+	Ciphertext + Auth Tag

This format allows the decryption tool to re-derive the key and decrypt the file securely.

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Usage

Open the App

Just open index.html in your browser — no internet or installation needed.

Encrypting a File

1. Click Choose File
2. Enter a password
3. Click Encrypt
4. Save the generated .enc file

Decrypting a File

1. Choose the .enc file
2. Enter the same password used to encrypt
3. Click Decrypt
4. The original file is downloaded with a .dec extension

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Requirements

• A modern browser:
  • Chrome
  • Firefox
  • Safari
  • Edge
  • Mobile browsers supported

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Security Tip

Always use a strong, unique password — the tool is only as secure as the password you choose.

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License

MIT License — free to use, modify, and distribute.

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Credits

Built by Marcus using nothing but love for crypto, privacy, and clean HTML (and a little AI). UI components by modest-ui.