A private writing tool

Back in 2018 I hacked together Words, a tiny writing API for two people. The point was simple: type, hit save, no friction, and keep our notes private without spinning up a database. It mattered to me because these were personal messages to my partner, and I wanted control over my data more than features. ✍️👇

Context and constraints, 2018-style: I created it on March 5, 2018, with “zero infra” in mind. PHP on any shared host, OpenSSL for crypto, JWT for sessions. Storage was JSON files on disk. One held the files path, a bcrypt password hash, a symmetric key, an IV, and a token lifetime of 25 hours. Scope was tiny by design: two humans, calm writing.

API sketch: POST / gave you a JWT, GET /posts listed titles and dates, PUT /posts created, and GET/PUT/DELETE worked by ID. Each post lived as a timestamp-prefixed JSON file. Title and body were encrypted then base64’d, date stayed plaintext for sorting. Upside: rsync-able backups, no migrations, two dependencies (OpenSSL + firebase/php-jwt), and a 10-minute install on any cheap PHP host.

What I learned the hard way:
- Not end-to-end: the server held the key and IV, so this was privacy at rest, not zero-knowledge.
- Reused IV across posts, which weakens semantic security and leaks patterns (short titles make this worse).
- Metadata leaked: filenames and dates in clear show activity rhythms even if content is encrypted.
- Long-lived JWTs, no refresh or revocation, rotation killed all sessions at once.
- Assumed a single writer, no filesystem locking meant possible race conditions.
- Search and tags needed decrypting everything, listing stayed O(n). Fine for two users, brittle beyond that.

If I built it today, I’d go client-side encryption with per-post random nonces (XChaCha20-Poly1305) and keys derived via Argon2id. Server stores opaque blobs. Secrets live in env with rotation. Sessions get short access tokens plus refresh, or plain server-side sessions, consider WebAuthn. Storage wise, a tiny SQLite with full-text search, or go local-first with CRDTs and encrypted sync.
Principles that still hold:
- State your threat model in the README.
- Minimize metadata, treat filenames and timestamps as sensitive.
- Per-item randomness is non-negotiable, rotate keys on a schedule.
- Keep tokens short-lived and revocable.
- Test backup-and-restore, not just backup.
- Be honest about “database-free” ergonomics before you commit.
Here’s the project: https://github.com/AnandChowdhary/words