Start LibreLedger: an encrypted money ledger that stores only ciphertext

LibreLedger is a single-person money ledger. The browser encrypts
everything (PBKDF2-HMAC-SHA256 with 250k iterations, then AES-256-GCM),
and a small standard-library Python server stores only the resulting
{v, salt, iv, ct} blob. Ledger files from the earlier Money Ledger version
open unchanged.

- On plain http to a LAN or VPN address, where browsers hide Web Crypto,
  the app switches to vendored @noble/hashes and @noble/ciphers 2.2.0 and
  says so on the lock screen. tests/crypto-interop.test.mjs shows both
  paths read each other's files.
- The server hands out only the app's own files, sends a self-only CSP,
  nosniff, frame denial and no-referrer, checks the shape of each blob,
  refuses cross-site writes and writes atomically. It keeps the last 10
  backups plus one per day for 30 days.
- The container runs that server from a digest-pinned python alpine
  image, as an unprivileged user, with its data in /data and a health
  check on /api/health.

Assisted-by: Claude Opus 5 <noreply@anthropic.com>

README.md

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+# LibreLedger
+
+An encrypted personal money ledger: **your data is encrypted in your browser;
+the server never sees it.**
+
+One screen, one continuous running balance:
+
+- **Balances** at the top: your accounts and their balances, with a grand total. That total is where the ledger *opens*.
+- **Monthly ledger** below: one block per month, a table of `Date · Type · Description · In · Out · Balance`. The balance runs on from your account balances and **carries from each month into the next**.
+  - **Type** comes from the row: money *in* shows a green **Money** badge, money *out* an amber **Cost** badge.
+  - Each row has a **category** (emoji and colour) for tagging entries at a glance.
+  - Insert or remove rows anywhere, and add or remove whole months.
+- **Recurring** bills and income (rent, phone, salary…), each with an amount, a category and a schedule:
+  - **Monthly** on a chosen day, **every N weeks** from an anchor date, or **yearly** on a month and day.
+  - **🔁 Add recurring** drops every matching occurrence into a month as real, editable rows; **+ Add month** moves to the next calendar month and pre-fills it.
+- **Totals**, **Savings** and **Housing affordability** summaries, several **budgets** in one ledger, CSV and PDF export.
+- **Dark / light theme**, dark by default.
+
+## Zero-knowledge encryption
+
+- Everything is encrypted **in the browser** with **AES-256-GCM**. The key is
+  derived from your passphrase with **PBKDF2-HMAC-SHA256, 250,000 iterations**
+  and a random 16-byte salt; each save uses a fresh random 12-byte IV.
+- The server (`server.py`) only stores and returns the resulting blob,
+  `{ "v": 1, "salt": …, "iv": …, "ct": … }` (base64). It never receives the
+  passphrase, the key or any figure from the ledger.
+- There is no account and no recovery. **Lose the passphrase and the data is
+  gone**; that is the point.
+- The page loads nothing from anywhere else. The server sends a strict
+  Content-Security-Policy (`'self'` only), `nosniff`, frame denial and
+  `no-referrer`, and serves only the app's own files.
+
+### Plain http on your LAN or VPN
+
+Browsers only give pages their built-in encryption (Web Crypto) in a *secure
+context*: HTTPS or `http://localhost`. Opened as `http://192.168.x.x:port` or
+over a VPN address, LibreLedger switches to its **built-in fallback**: the same
+PBKDF2-SHA256 and AES-256-GCM from the audited
+[@noble/hashes](https://github.com/paulmillr/noble-hashes) and
+[@noble/ciphers](https://github.com/paulmillr/noble-ciphers) libraries,
+vendored and pinned in [`vendor/`](vendor/README.md). The files it writes are
+identical in format, so a ledger saved one way opens the other way.
+
+The lock screen says when the fallback is in use. Unlocking takes a few seconds
+longer, and the key sits in page memory rather than in the browser's key store,
+so **prefer HTTPS** whenever you have it. Plain http also means anyone on the
+network path can see (encrypted) traffic and could tamper with the page itself,
+so only use it on a network you trust.
+
+## Self-hosting
+
+### Docker
+
+```bash
+docker run -d --name libreledger -p 127.0.0.1:8080:8080 \
+  -v libreledger-data:/data \
+  git.libreportal.org/libreportal/libreledger:1.0.0
+# open http://localhost:8080
+```
+
+Or build it yourself: `docker build -t libreledger .`
+
+The image runs `server.py` on port 8080 as an unprivileged user, keeps its data
+in the `/data` volume and has a health check on `/api/health`. Put HTTPS in
+front of it (Caddy, Traefik, nginx…) when it is reachable from anywhere but
+your own machine.
+
+### Without Docker
+
+```bash
+python3 server.py                          # http://127.0.0.1:8080, data in ./data
+python3 server.py --host 0.0.0.0 --port 8080 --data-dir /srv/libreledger
+```
+
+Python 3.9 or newer, standard library only.
+
+| Option | Environment | Default |
+| --- | --- | --- |
+| `--host` | `LIBRELEDGER_HOST` | `127.0.0.1` |
+| `--port` | `LIBRELEDGER_PORT` | `8080` |
+| `--data-dir` | `LIBRELEDGER_DATA_DIR` | `./data` |
+| `--backup-interval` | `LIBRELEDGER_BACKUP_INTERVAL` | `600` seconds (`0`: every save) |
+| `--backup-keep-recent` | `LIBRELEDGER_BACKUP_KEEP_RECENT` | `10` |
+| `--backup-keep-daily` | `LIBRELEDGER_BACKUP_KEEP_DAILY` | `30` |
+
+### Your data
+
+- `<data-dir>/ledger.enc` is the ledger, written atomically on every change.
+- `<data-dir>/backups/ledger-<UTC time>.enc` are earlier versions: the newest
+  10, plus the last one of each of the most recent 30 days. At most one is taken
+  per backup interval.
+- All of them are encrypted with the passphrase that was current when they were
+  written. To restore one, stop the server and copy it over `ledger.enc`, or
+  use **Restore** in the app.
+- To move a ledger to another server, copy `ledger.enc` into its data folder
+  and unlock it with your passphrase. Files from the earlier "Money Ledger"
+  version of this app work as they are.
+
+The server has no login of its own: anyone who can reach it can fetch the
+encrypted file or overwrite it (the backups cover the latter). Keep it on a
+private network, a VPN, or behind an authenticating proxy.
+
+### Install on LibrePortal
+
+LibreLedger is in the [LibrePortal](https://git.libreportal.org/LibrePortal/LibrePortal)
+app catalog: `libreportal app install libreledger`, or **Apps → LibreLedger**
+in the WebUI. It installs *private* (reachable only from your trusted places),
+with its data included in LibrePortal's backups, and on
+`https://ledger.<your domain>` when a domain is set up.
+
+## In the app
+
+- **💾 Saved to disk**: the encrypted ledger is saving to the server.
+- **🔗 Link file** *(Chrome/Edge desktop, when opened without the server)*:
+  auto-save to an encrypted file you choose.
+- **Export CSV / PDF**: plaintext exports of the decrypted data. Handle them with care.
+- **Backup / Restore**: download or load an *encrypted* copy.
+- **Change passphrase**: re-encrypts with a new passphrase. Older backups keep the old one.
+- **Lock**: forgets the key and the data; the passphrase is needed again.
+
+## Development
+
+```bash
+python3 tests/test_server.py                 # server: allowlist, headers, checks, backups
+node tests/crypto-interop.test.mjs           # Web Crypto <-> fallback interop (Node 22.12+)
+```
+
+Files: `index.html` (markup and lock screen), `styles.css`, `app.js` (state,
+rendering and the crypto layer), `theme.js`, `crypto-fallback.js`, `server.py`,
+`banks/` (logos, see `banks/NOTICE.txt`), `vendor/`.
+
+## Licence
+
+[GNU AGPLv3](LICENSE). The vendored noble libraries are MIT-licensed (their
+`LICENSE` files are next to them); bank logos are trademarks of their owners
+(`banks/NOTICE.txt`).