BlindCrypt

BlindCrypt is a static web app for client-side file encryption and decryption. Your passphrase and plaintext stay in your browser.

Features

• Encrypt a file with a passphrase and download a .blindcrypt file
• Decrypt a .blindcrypt file with the passphrase and download the original
• Passphrase generator with adjustable security levels
• Versioned file format for future compatibility

Security model

• Encryption and decryption occur locally via WebCrypto
• Server only hosts static files
• If the endpoint is compromised (malware, hostile browser extensions), no web app can protect the data

Algorithms

• Cipher: AES-256-GCM (authenticated encryption)
• KDF: PBKDF2 with SHA-256
• Randomness: crypto.getRandomValues

This starter uses PBKDF2 to remain dependency-free for GitHub Pages. For stronger GPU-resistant derivation, replace PBKDF2 with Argon2id via WASM.

Passphrase word list

BlindCrypt uses the 2048 word BIP39 English word list (bundled in assets/wordlist.js).

File format

[4 bytes big-endian header length][header JSON UTF-8][ciphertext bytes]

The header contains version, KDF parameters, salt, IV, and original filename/type.

Run locally

Use a local web server (recommended):

python -m http.server 8080

Then visit http://localhost:8080.

Host on GitHub Pages

1. Push this repo to GitHub
2. Settings -> Pages
3. Source: Deploy from a branch
4. Branch: main and folder /root
5. Save

License

MIT