# Device security

End-to-end encryption protects a message in transit. This page is about the other half: the key sitting on your device, and getting rid of it in a hurry.

For the transit half — including the optional [quantum-resistant encryption](https://nymchat.app/docs/post-quantum/) for private messages and group chats — see those pages instead.

## Identity encryption

By default a saved private key sits in the device's local storage in the clear. Anyone who can read that storage — an unlocked device, a forensic tool, a browser profile copied off a shared machine — can read the key and become you.

**Identity Encryption**, under Settings › Privacy & Security, closes that hole. With it on:

- your `nsec` is encrypted at rest with **AES-GCM-256**;
- the ephemeral secret keys your [group chats](https://nymchat.app/docs/groups/) rely on are encrypted under the same vault key;
- the plaintext key is never written to disk while encryption is on — it exists only in memory, only for the session;
- unlocking happens once, when the app starts.

![The Privacy and Security settings section, with Identity Encryption at the top.](https://nymchat.app/images/docs/settings-privacy.webp)

*Identity Encryption sits at the top of Privacy & Security.*

> **This one setting does not sync**
>
> The unlock factor and the encrypted key are local to a device, so identity encryption is enabled **per device**. Only a non-sensitive on/off preference travels between devices, so a new device can offer to set it up too. No password, salt or credential is ever synced.

## Choosing an unlock factor

You pick how the vault is unlocked on this device:

| Factor | How the key is derived | Available on |
| --- | --- | --- |
| Password | PBKDF2-SHA256, 310 000 iterations | Everywhere |
| PIN | The same PBKDF2 derivation, digits only | Everywhere |
| Passkey | WebAuthn with the PRF extension, then HKDF-SHA256 | Web app |
| Biometric — Face ID, Touch ID, Windows Hello, Android biometrics, a hardware security key | WebAuthn PRF on the web; the platform's own biometric prompt on Android and iOS | Everywhere |

A PIN is a password made of digits, so treat a short one as exactly that: quick, and weak.

> **Why it asks you to unlock straight away**
>
> Not every authenticator implements the WebAuthn PRF extension, and one that does not cannot derive a key. So the moment you enable encryption the app makes you unlock once, there and then — better to find out immediately than the next time you open the app with no way back in.

## Panic wipe

**Press and hold the "Your Nym" panel for two seconds.** Nymchat destroys every trace of itself on the device. There is no confirmation dialog, on purpose — the point is that it can be triggered fast, under pressure, without a second screen to get through.

A short animation shows the progress while it:

1. drops the private key and the vault key from memory;
2. encrypts every local- and session-storage value under a fresh random key that is *immediately discarded*, then overwrites those values with junk and clears the stores;
3. overwrites and deletes every IndexedDB database;
4. empties the cache storage and unregisters the service worker;
5. clears cookies, then reloads to a pristine first-run state.

Step two is the interesting one. Deleting data does not necessarily make it unrecoverable, so the app encrypts it first under a key nobody — including the app — keeps. Whatever survives the delete is ciphertext with no key in existence.

> **There is no undo**
>
> A wiped identity is not recoverable, by you or by anyone. If the nym is one you want to keep, back up its `nsec` before you ever need this. A normal single tap on that panel just opens the nym editor, so a wipe does not happen by accident.

## What is stored on your device

Nymchat keeps state locally so it can open instantly and work offline. Broadly:

| What | Notes |
| --- | --- |
| Your keypair | Encrypted at rest when identity encryption is on. Not stored at all in per-session or hardcore mode. |
| Settings and preferences | Theme, layout, blocked users and keywords, favorite channels, and the rest. |
| Channel history and profiles | A cache of what has been fetched from relays. |
| Decrypted private messages and group chats | Controlled by *Cache PMs & Group Chats On Device* (on by default). Turn it off and they are re-fetched and decrypted each launch instead of sitting on disk. |
| Group membership and ephemeral group keys | Encrypted under the vault key when identity encryption is on. |
| Flair purchases | Recoverable from a redeem code — see [the flair shop](https://nymchat.app/docs/lightning/#shop). |

Settings › Data & Backup has two narrower tools than the panic wipe: **Clear Local Storage Cache** drops cached history, messages, profiles and reactions but keeps your login, settings, group memberships and purchases; **Reset Settings to Defaults** does the reverse.