Cryptography · 7 min read · 2026-11-08

Zero-Knowledge Browser Cryptography: AES-256-GCM, PBKDF2, and Self-Decrypting HTML Envelopes

Key Takeaway

How to encrypt confidential notes and recovery keys in your browser so recipients can unlock them offline in any web browser without installing software.

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PrivacyFold's **Password-protect text** utility uses the W3C `crypto.subtle` API to derive a 256-bit key via **PBKDF2-SHA256 (100,000 iterations)** with a random 128-bit salt, encrypts your cleartext with **AES-256-GCM**, and packages the ciphertext into a standalone, offline-unlockable `.html` file.

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Run the client-side tool explained in this guide with zero server uploads.

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