User: describe the encryption flow for wifi credentials (settings.html + Wireless.ino)

GitHub Copilot: I'll open settings.html, Wireless.ino, and `crypto.cpp/crypto.h` to trace how Wi‑Fi credentials are encrypted and handled.

Read [](file:///g%3A/src/vscode/AIRmatic/data/settings.html#1-1), lines 1 to 400

Read [](file:///g%3A/src/vscode/AIRmatic/data/settings.html#400-400), lines 400 to 575

Now I'll open Wireless.ino to see the server-side handling of the session, seeds, and encryption.

Read [](file:///g%3A/src/vscode/AIRmatic/Wireless.ino#1-1), lines 1 to 400

Read [](file:///g%3A/src/vscode/AIRmatic/Wireless.ino#400-400), lines 400 to 468

Read [](file:///g%3A/src/vscode/AIRmatic/crypto.h)

Read [](file:///g%3A/src/vscode/AIRmatic/crypto.cpp#1-1), lines 1 to 400

Read [](file:///g%3A/src/vscode/AIRmatic/crypto.cpp#400-400), lines 400 to 424

Now I'll add a short TODO plan for tracking the task steps.

Created 3 todos

Progress: inspected settings.html, Wireless.ino, and crypto.cpp; below is the concise end‑to‑end flow.

- **Client file:** settings.html — `generateSessionKey()`, `readWifi()`, `readPw()`, `updateWifi()`, `rebootWifi()`.  
- **Server files:** Wireless.ino + crypto.cpp — `server` routes, `generateKeys()`, `cryptUpdateWifi()`, `cryptGetWifi()`, RSA/AES helpers.

Step-by-step flow
- **Get server public key:** Client fetches `/public.pem` (served by Wireless.ino) and loads it (forge) for RSA encrypt.  
- **Session creation (client):** Client generates two random byte arrays: `random1` (challenge) and `salt` (one‑time symmetric key). It computes:
  - `challenge = AES-ECB(random1, salt)` → hex -> stored as `cachedJson.wifi.seed`.
  - `encSeedB64 = RSA-OAEP_encrypt(salt, server_public_pem)` -> stored as `cachedJson.wifi.salt` (base64).
  Then POSTs `update=5` (via `/config`) so server receives these two values. (See `generateSessionKey()` in settings.html.)
- **Session handling (server):** `cryptUpdateWifi()` (in crypto.cpp):
  - Base64-decodes `cachedJson.wifi.salt` and RSA-decrypts with the private key → recovers `fw_key` (the original `salt`).
  - Hex-decodes `cachedJson.wifi.seed` and AES-decrypts with `fw_key` → recovers `challenge` (original `random1`).
  - Derives `pseudoKey = junkHash(fw_key)` and `response = junkHash(challenge)`, then encrypts `response` with `pseudoKey` → `random2`.
  - Encrypts current device `ssid` with `fw_key` and `password` (after `junkHash`) with `pseudoKey`, converts them to hex and returns them as `hash` and `seed`. It sets `salt` (in JSON) to hex(`random2`). Then server sends the updated JSON back to client (via `updateJson()` / `/config`).
- **Client verifies server (client):** `readWifi()`:
  - Reads `cachedJson.wifi.salt` (now hex `random2`) and `cachedJson.wifi.hash`.
  - Computes `pseudoKey = junkHash(salt)` where `salt` is the original client `salt` (recovered locally).
  - Decrypts server `salt` (hex→bytes) with `pseudoKey` to get `random2_plain`. Checks `handshake(junkHash(random1), random2_plain)` to verify server holds the private key and decrypted `salt`. If OK, client uses AES-decrypt with `salt` to recover and show current SSID.
- **Password check (client):** `readPw()`:
  - Builds `pwdhash = junkHash(oldpw)` and computes `enc_hash = AES-ECB(pwdhash, pseudoKey)`.
  - Compares `enc_hash` with the previously-sent `seed` (which holds challenge/encrypted data) via `handshake()` to verify the supplied old password matches the stored password proof.
- **Update credentials (client → server):** `updateWifi()`:
  - If password change: client AES-encrypts new SSID and new password with `salt` and `pseudoKey` as appropriate, stores hex strings into `cachedJson.wifi.hash`, `.seed`, and sets `.salt` to AES-ECB(random1, pseudoKey) hex (a confirmation challenge), then POSTs `update=6`.
- **Server apply update (server):** `cryptGetWifi()`:
  - Verifies session by comparing AES-encrypted confirmation values (handshake). If valid:
    - Hex-decodes incoming `hash`/`seed` → AES-decrypts with `fw_key` and/or `pseudoKey` to obtain plaintext SSID/password.
    - Derives device-local `hw_key` from eFuse MAC (`getMac(hw_key)`), re-encrypts credentials with `hw_key` (AES-ECB) for persistent storage, sets `hash`, `seed`, `salt` in JSON to the server-side confirmation values, and returns success. It then schedules reboot to apply Wi‑Fi change.
- **Persistence & reboot:** Server stores the hw‑key‑encrypted credentials (LittleFS) and reboots to apply the new STA credentials.

Key implementation notes
- **Primitives used:** RSA-OAEP (SHA1) for encrypting the ephemeral `salt` (client → server), AES-ECB for all symmetric encryption, and a custom `junkHash()` as a deterministic scrambling/derivation function. RSA keypair is generated/stored on device (`/private.pem` + `/public.pem`). (See crypto.cpp.)
- **Where to look:** client logic in `generateSessionKey()`, `readWifi()`, `readPw()`, `updateWifi()` in settings.html; server handlers and `cryptUpdateWifi()` / `cryptGetWifi()` in crypto.cpp and their routing in Wireless.ino.

Want a brief security summary (pros/cons and suggested improvements)?