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<main id="usage">
<h1><a href="#usage">Usage guide</a></h1>
<p>This is a guide covering some aspects of using GrapheneOS. See the
<a href="/features">features page</a> for a list of GrapheneOS features.</p>
<nav id="table-of-contents">
<h2><a href="#table-of-contents">Table of contents</a></h2>
<ul>
<li>
<a href="#system-navigation">System navigation</a>
<ul>
<li><a href="#gesture-navigation">Gesture navigation</a></li>
<li><a href="#2-button-navigation">2-button navigation</a></li>
<li><a href="#3-button-navigation">3-button navigation</a></li>
</ul>
</li>
<li><a href="#accessibility">Accessibility</a></li>
<li><a href="#auditor">Auditor</a></li>
<li>
<a href="#updates">Updates</a>
<ul>
<li><a href="#updates-settings">Settings</a></li>
<li><a href="#updates-security">Security</a></li>
<li><a href="#updates-disabling">Disabling</a></li>
<li><a href="#updates-sideloading">Sideloading</a></li>
</ul>
</li>
<li><a href="#web-browsing">Web browsing</a></li>
<li><a href="#camera">Camera</a></li>
<li><a href="#exec-spawning">Exec spawning</a></li>
<li><a href="#bugs-uncovered-by-security-features">Bugs uncovered by security features</a></li>
<li>
<a href="#wifi-privacy">Wi-Fi privacy</a>
<ul>
<li><a href="#wifi-privacy-scanning">Scanning</a></li>
<li><a href="#wifi-privacy-associated">Associated with an Access Point (AP)</a></li>
</ul>
</li>
<li><a href="#lte-only-mode">LTE-only mode</a></li>
</ul>
</nav>
<section id="accessibility">
<h2><a href="#accessibility">Accessibility</a></h2>
<p>GrapheneOS includes all of the accessibility features from the Android Open
Source Project and strives to fill in the gaps from not including Google apps and
services. We include our own fork of the open source TalkBack and Switch Access
accessibility services along with a Monochromacy option for the standard color
correction menu.</p>
<p>GrapheneOS does not yet include a text-to-speech (TTS) service in the base OS
due to limitations of the available options. Including one is planned in the
future when a suitable option is available. RHVoice and eSpeak NG are both open
source and are the most common choices by GrapheneOS users. Both of these mostly
work fine but have licensing issues and don't support Direct Boot so they cannot
be used before the initial unlock of the device. Installing and setting up either
one of these or another TTS app will get TalkBack working. TalkBack itself
supports Direct Boot and works before the first unlock but it needs to have a TTS
app supporting it in order to do more than playing the activation sound before the
first unlock. After installing a TTS service, you need to select it in the OS
configuration to accept activating it. The OS will display one of them as already
selected but it won't simply work from being installed as that wouldn't be safe.
This is the same as the stock OS but it comes with one set up already.</p>
<p>GrapheneOS disables showing the characters as passwords are typed by default.
You can enable this in Settings ➔ Privacy.</p>
<p>Third party accessibility services can be installed and activated. This
includes the ones made by Google. Most of these will work but some may have a hard
dependency on functionality from Google Play services for some of their
functionality or to run at all. Accessibility services are very powerful and we
strongly recommend against using third party implementations if you can get by
well without them. We plan to add safeguards in this area while still keeping them
working without problematic barriers.</p>
</section>
<section id="system-navigation">
<h2><a href="#system-navigation">System navigation</a></h2>
<p>By default, GrapheneOS uses gesture-based navigation. We recommend reading our
guide on gesture navigation and giving it a chance even if you think you won't
like it. Our experience is that when armed with the appropriate knowledge, the
vast majority of users prefer the newer gesture navigation approach.</p>
<p>The system navigation mode can be configured in Settings → System → Gestures →
System navigation. The same menu is also available in Settings → Accessibility →
System navigation.</p>
<section id="gesture-navigation">
<h3><a href="#gesture-navigation">Gesture navigation</a></h3>
<p>The bottom of the screen is a reserved touch zone for system navigation. A
line is displayed in the center to show that the navigation bar is present
across the entire bottom of the screen. In most apps, this area will display
padding. Modern apps are able to tell the OS that they can handle not having
the padding to display app content there while still not being able to receive
touches from it. Open up the Settings app for an example.</p>
<p>Swiping up from the navigation bar while removing your finger from the
screen is the <strong>Home</strong> gesture.</p>
<p>Swiping up from the navigation bar while holding your finger on the screen
before releasing is the <strong>Recent Apps</strong> gesture. The most
recently opened activity is always on the furthest right. Each step left goes
one step back through the history of recently opened apps. Opening an app with
the recent apps activity will place it on the furthest right in the recent
apps order just like a new app being opened.</p>
<p>The recent apps activity has a screenshot button as an alternative to
holding power and volume down while using an app.</p>
<p>Rather than opening the recent apps activity, you can swipe left on the
navigation bar for the <strong>Previous</strong> app and swipe right for the
<strong>Next</strong> app. This will not change the recent apps order. This is
usually the best way to navigate through recent apps.</p>
<p>Swiping from either the left or the right of the screen within the app (not
the navigation bar) is the <strong>Back</strong> gesture. Apps are supposed to
avoid implementing conflicting gestures, but have the option to override this
gesture if they truly need to get rid of it. However, many apps without active
development of their UI design still haven't addressed this despite gestures
being the default for 2 years on Google Android. You can avoid triggering the
back gesture in one of 2 easy ways: avoid swiping from right near the edge or
hold your finger on the side of the screen for a moment before swiping. The
more advanced option is using a diagonal swipe pointing sharply to the bottom
of the screen since this will bypass the back gesture but will still trigger
most app gestures. The advanced option is the most convenient approach once
you get used to doing it.</p>
<p>The launcher uses a swipe up gesture starting anywhere on the screen to
open the app drawer from the home screen. You need to start that gesture above
the system navigation bar since any gesture starting on the navigation bar is
handled by the OS as a system navigation gesture.</p>
</section>
<section id="2-button-navigation">
<h3><a href="#2-button-navigation">2-button navigation</a></h3>
<p>2-button navigation is a legacy mode not supported anymore by Google
Android on the Pixel 4 and later. It will likely be removed in a future
release of GrapheneOS. You should use <a href="#3-button-navigation">3-button
navigation</a> if you want the traditional button-based navigation.</p>
<p>A large row across the bottom of the screen is reserved for navigation
buttons. The <strong>Back</strong> button is on the left and the
<strong>Home</strong> button is in the center.</p>
<p>Swiping up from the navigation bar while removing your finger from the
screen is the <strong>Recent apps</strong> gesture. The most recently opened
activity is always on the furthest right. Each step left goes one step back
through the history of recently opened apps. Opening an app with the recent
apps activity will place it on the furthest right in the recent apps
order just like a new app being opened.</p>
<p>2-button navigation provides the recent apps activity with the launcher. It
shows the recent apps above the bottom row of the home screen and the search
integration not used in GrapheneOS. The usual launcher features work including
swiping up anywhere on the screen to open the app drawer. Due to the launcher
integration, the screenshot button available in the other modes isn't present.
Instead, a screenshot button is added to the global action menu accessed by
holding the power button.</p>
</section>
<section id="3-button-navigation">
<h3><a href="#3-button-navigation">3-button navigation</a></h3>
<p>3-button navigation is Android's oldest touchscreen-based navigation
system. It will remain supported for the foreseeable future to provide
accessibility for users unable to easily use the gestures. It's older than
2-button navigation but isn't considered a legacy feature.</p>
<p>A large row across the bottom of the screen is reserved for navigation
buttons. The <strong>Back</strong> button is on the left, the
<strong>Home</strong> button is in the center and the <strong>Recent
Apps</strong> button is on the right.</p>
<p>In the recent apps activity, the most recently opened activity is always on
the furthest right. Each step left goes one step back through the history of
recently opened apps. Opening an app with the recent apps activity will place
it on the furthest right in the recent apps order just like a new app being
opened.</p>
<p>The recent apps activity has a screenshot button as an alternative to
holding power and volume down while using an app.</p>
</section>
</section>
<section id="auditor">
<h2><a href="#auditor">Auditor</a></h2>
<p>See the <a href="https://attestation.app/tutorial">tutorial page on the site for the attestation sub-project</a>.</p>
</section>
<section id="updates">
<h2><a href="#updates">Updates</a></h2>
<p>The update system implements automatic background updates. It checks for updates
approximately once every four hours when there's network connectivity and then
downloads and installs updates in the background. It will pick up where it left off if
downloads are interrupted, so you don't need to worry about interrupting it.
Similarly, interrupting the installation isn't a risk because updates are installed to
a secondary installation of GrapheneOS which only becomes the active installation
after the update is complete. Once the update is complete, you'll be informed with a
notification and simply need to reboot with the button in the notification or via a
normal reboot. If the new version fails to boot, the OS will be rolled back to the
past version and the updater will attempt to download and install the update
again.</p>
<p>The updater will use incremental (delta) updates to download only changes rather
than the whole OS when one is available to go directly from the installed version to
the latest version. As long as you have working network connectivity on a regular
basis and reboot when asked, you'll almost always be on one of the past couple
versions of the OS which will minimize bandwidth usage since incrementals will always
be available.</p>
<p>The updater works while the device is locked / idle, including before the first
unlock since it's explicitly designed to be able to run before decryption of user
data.</p>
<p>Release changelogs are available <a href="/releases#changelog">in a section on the releases page</a>.</p>
<section id="updates-settings">
<h3><a href="#updates-settings">Settings</a></h3>
<p>The settings are available in the Settings app in System ➔ Advanced ➔ Update
settings.</p>
<p>The "Check for updates" option will manually trigger an update check as soon as
possible. It will still wait for the configuration conditions listed below to be
satisfied, such as being connected to the internet via one of the permitted network
types.</p>
<p>The "Release channel" setting can be changed from the default Stable channel to the
Beta channel if you want to help with testing. The Beta channel will usually simply
follow the Stable channel, but the Beta channel may be used to experiment with new
features.</p>
<p>The "Permitted networks" setting controls which networks will be used to perform
updates. It defaults to using any network connection. It can be set to "Non-roaming"
to disable it when the cellular service is marked as roaming or "Unmetered" to disable
it on cellular networks and also Wi-Fi networks marked as metered.</p>
<p>The "Require battery above warning level" setting controls whether updates will
only be performed when the battery is above the level where the warning message is
shown. The standard value is at 15% capacity.</p>
<p>Enabling the opt-in "Automatic reboot" setting allows the updater to reboot the
device after an update once it has been idle for a long time. When this setting is
enabled, a device can take care of any number of updates completely automatically even
if it's left completely idle.</p>
</section>
<section id="updates-security">
<h3><a href="#updates-security">Security</a></h3>
<p>The update server isn't a trusted party since updates are signed and verified along
with downgrade attacks being prevented. The update protocol doesn't send identifiable
information to the update server and works well over a VPN / Tor. GrapheneOS isn't
able to comply with a government order to build, sign and ship a malicious update to a
specific user's device based on information like the IMEI, serial number, etc. The
update server only ends up knowing the IP address used to connect to it and the
version being upgraded from based on the requested incremental.</p>
<p>Android updates can support serialno constraints to make them validate only on a
certain device but GrapheneOS rejects any update with a serialno constraint for both
over-the-air updates (Updater app) and sideloaded updates (recovery).</p>
</section>
<section id="updates-disabling">
<h3><a href="#updates-disabling">Disabling</a></h3>
<p>It's highly recommended to leave automatic updates enabled and to configure the
permitted networks if the bandwidth usage is a problem on your mobile data connection.
However, it's possible to turn off the update client by going to Settings ➔ Apps,
enabling Show system via the menu, selecting Seamless Update Client and disabling the
app. If you do this, you'll need to remember to enable it again to start receiving
updates.</p>
</section>
<section id="updates-sideloading">
<h3><a href="#updates-sideloading">Sideloading</a></h3>
<p>Updates can be downloaded via
<a href="https://grapheneos.org/releases">the releases page</a> and installed via recovery
with adb sideloading. The zip files are signed and verified by recovery, just as they
are by the update client within the OS. This includes providing downgrade protection,
which prevents attempting to downgrade the version. If recovery didn't enforce these
things, they would still be enforced via verified boot including downgrade protection
and the attempted update would just fail to boot and be rolled back.</p>
<p>To install one by sideloading, first, boot into recovery. You may do this either by
using <code>adb reboot recovery</code> from the operating system, or by selecting the
"Recovery" option in the bootloader interface.</p>
<p>You should see the green Android lying on its back being repaired, with the text "No
command" meaning that no command has been passed to recovery.</p>
<p>Next, access the recovery menu by holding down the power button and pressing the volume
up button a single time. This key combination toggles between the GUI and text-based mode
with the menu and log output.</p>
<p>Finally, select the "Apply update from ADB" option in the recovery menu and
sideload the update with adb. For example:</p>
<pre>adb sideload blueline-ota_update-2019.07.01.21.zip</pre>
<p><strong>You do not need to have adb enabled within the OS or the host's ADB key
whitelisted within the OS to sideload an update to recovery. Recovery mode does not
trust the attached computer and this can be considered a production feature. Trusting
a computer with ADB access within the OS is much different and exposes the device to a
huge amount of attack surface and control by the trusted computer.</strong></p>
</section>
</section>
<section id="usb-peripherals">
<h2><a href="#usb-peripherals">USB peripherals</a></h2>
<p>GrapheneOS defaults to ignoring connected USB peripherals when the device is
already booted and the screen is locked. A USB device already connected at boot
will still work. The purpose is reducing attack surface for a locked device with
active login sessions to user profiles to protect data that's not at rest. This
can be controlled in Settings ➔ Security ➔ USB accessories. The options are:</p>
<ul>
<li>Disallow new USB peripherals</li>
<li>Allow new USB peripherals when unlocked (default)</li>
<li>Allow new USB peripherals (like stock Android)</li>
</ul>
<p>This option has no impact on the device acting as a USB peripheral itself when
connected to a computer. Android defaults to charge only mode and requires opt-in
to the device being used for file transfer, USB tethering, MIDI or PTP.</p>
</section>
<section id="web-browsing">
<h2><a href="#web-browsing">Web browsing</a></h2>
<p>GrapheneOS includes a Vanadium subproject providing privacy and security enhanced
releases of Chromium. Vanadium is both the user-facing browser included in the OS and
the provider of the WebView used by other apps to render web content. The WebView is
the browser engine used by the vast majority of web browsers and nearly all other apps
embedding web content or using web technologies for other uses.</p>
<p>Using Vanadium is highly recommended. Bromite is a solid alternative and is the
only other browser we recommend. Bromite provides integrated ad-blocking and more
advanced anti-fingerprinting. For now, Vanadium is more focused on security hardening
and Bromite is more focused on anti-fingerprinting. The projects are collaborating
together and will likely converge to providing more of the same features. Vanadium
will be providing content filtering and anti-fingerprinting, but it needs to be done
in a way that meets the standards of the project, which takes time.</p>
<p>Vanadium is designed for use on GrapheneOS and does not duplicate the OS privacy
and security features such as the hardened malloc implementation. This leads to some
of the differences from Bromite, such as relying on OS support for encrypted DNS
rather than enabling Chromium's DNS-over-HTTPS support.</p>
<p>Chromium-based browsers like Vanadium and Bromite provide the strongest sandbox
implementation, leagues ahead of the alternatives. It is much harder to escape from
the sandbox and it provides much more than acting as a barrier to compromising the
rest of the OS. Site isolation enforces security boundaries around each site using the
sandbox by placing each site into an isolated sandbox. It required a huge overhaul of
the browser since it has to enforce these rules on all the IPC APIs. Site isolation is
important even without a compromise, due to side channels. Browsers without site
isolation are very vulnerable to attacks like Spectre. On mobile, due to the lack of
memory available to apps, there are different modes for site isolation. Vanadium turns
on strict site isolation, matching Chromium on the desktop. Bromite enables strict
site isolation on high memory devices, including all the devices that are officially
supported by GrapheneOS.</p>
<p>Chromium has decent exploit mitigations, unlike the available alternatives. This is
improved upon in Vanadium by enabling further mitigations, including those developed
upstream but not yet fully enabled due to code size, memory usage or performance. For
example, it enables type-based CFI like Chromium on the desktop, uses a stronger SSP
configuration, zero initializes variables by default, etc. Some of the mitigations are
inherited from the OS itself, which also applies to other browsers, at least if they
don't do things to break them.</p>
<p>We recommend against trying to achieve browser privacy and security through piling
on browser extensions and modifications. Most privacy features for browsers are
privacy theater without a clear threat model and these features often reduce privacy
by aiding fingerprinting and adding more state shared between sites. Every change you
make results in you standing out from the crowd and generally provides more ways to
track you. Enumerating badness via content filtering is not a viable approach to
achieving decent privacy, just as AntiVirus isn't a viable way to achieving decent
security. These are losing battles, and are at best a stopgap reducing exposure while
waiting for real privacy and security features.</p>
<p>Vanadium will be following the school of thought where hiding the IP address
through Tor or a trusted VPN shared between many users is the essential baseline, with
the browser partitioning state based on site and mitigating fingerprinting to avoid
that being trivially bypassed. The Tor Browser's approach is the only one with any
real potential, however flawed the current implementation may be. This work is
currently in a very early stage and it is largely being implemented upstream with the
strongest available implementation of state partitioning. Chromium is using Network
Isolation Keys to divide up connection pools, caches and other state based on site and
this will be the foundation for privacy. Chromium itself aims to prevent tracking
through mechanisms other than cookies, greatly narrowing the scope downstream work
needs to cover. Bromite is doing a lot of work in these areas and Vanadium will be
benefiting from that along with this upstream work. The focus is currently on research
since we don't see much benefit in deploying bits and pieces of this before everything
is ready to come together. At the moment, the only browser with any semblance of
privacy is the Tor Browser but there are many ways to bypass the anti-fingerprinting
and state partitioning. The Tor Browser's security is weak which makes the privacy
protection weak. The need to avoid diversity (fingerprinting) creates a monoculture
for the most interesting targets. This needs to change, especially since Tor itself
makes people into much more of a target (both locally and by the exit nodes).</p>
<p>WebView-based browsers use the hardened Vanadium rendering engine, but they can't
offer as much privacy and control due to being limited to the capabilities supported
by the WebView widget. For example, they can't provide a setting for toggling sensors
access because the feature is fairly new and the WebView WebSettings API doesn't yet
include support for it as it does for JavaScript, location, cookies, DOM storage and
other older features. For sensors, the Sensors app permission added by GrapheneOS can
be toggled off for the browser app as a whole instead. The WebView sandbox also
currently runs every instance within the same sandbox and doesn't support site
isolation.</p>
<p>Avoid Gecko-based browsers like Firefox as they're currently much more vulnerable
to exploitation and inherently add a huge amount of attack surface. Gecko doesn't have
a WebView implementation (GeckoView is not a WebView implementation), so it has to be
used alongside the Chromium-based WebView rather than instead of Chromium, which means
having the remote attack surface of two separate browser engines instead of only one.
Firefox / Gecko also bypass or cripple a fair bit of the upstream and GrapheneOS
hardening work for apps. Worst of all, Firefox runs as a single process on mobile and
has no sandbox beyond the OS sandbox. This is despite the fact that Chromium semantic
sandbox layer on Android is implemented via the OS <code>isolatedProcess</code>
feature, which is a very easy to use boolean property for app service processes to
provide strong isolation with only the ability to communicate with the app running
them via the standard service API. Even in the desktop version, Firefox's sandbox is
still substantially weaker (especially on Linux, where it can hardly be considered a
sandbox at all) and lacks support for isolating sites from each other rather than only
containing content as a whole.</p>
</section>
<section id="camera">
<h2><a href="#camera">Camera</a></h2>
<p>The Camera app included in GrapheneOS is very basic and can't take full advantage
of the hardware. It doesn't offer much in the way of configuration. In the long term,
it's going to be replaced. In the short term, there are other apps available providing
more capabilities and better support for taking advantage of the hardware.</p>
<p>The Pixel 3 (but not the Pixel 3a) and Pixel 4 (but not the Pixel 4a) have a
Pixel Visual Core / Pixel Neural Core providing a hardware-based implementation of
HDR+. HDR+ captures many images and intelligently merges data across them, taking
into account motion, etc. It substantially improves the quality of images,
especially in low light. This is used transparently for third party apps that are
compatible with it, and there isn't an explicit switch to turn it on or off for
most of them. An example of a compatible app is Open Camera's default
configuration, or Open Camera with the Camera 2 API and other settings (including
the the various knobs / toggles outside of the settings menu) left alone. In
general, HDR+ will work transparently in most apps as long as they keep things
simple and use a good minimalist approach to taking pictures. It should work
transparently in most messaging apps, etc. with internal support for taking
pictures.</p>
<p>In addition to supporting HDR+ via the Pixel Visual Core, or similar features on
other devices with the same constraints, Open Camera offers advanced configuration and
various advanced features. Make sure to enable the Camera 2 API in the settings, which
should be the default, but the app doesn't have a great user interface / user
experience. You probably don't want to use the traditional HDR feature in the app.
That's not HDR+, but rather captures 3 images and merges them in a way that isn't at
all intelligent and causes a lot of blur and distortion. The HDR+ implementation can
actually benefit from the camera not being completely steady as it's smart enough to
match up the picture and it provides it with more data vs. a traditional HDR
implementation where it essentially doesn't work without a tripod and is not really at
all useful on a phone unless you actually have that for it.</p>
</section>
<section id="exec-spawning">
<h2><a href="#exec-spawning">Exec spawning</a></h2>
<p>GrapheneOS creates fresh processes (via exec) when spawning applications instead of
using the traditional Zygote spawning model. This improves privacy and security at the
expense of higher cold start app spawning time and higher initial memory usage. It
doesn't impact runtime performance beyond the initial spawning time. It adds somewhere
in the ballpark of 100ms to app spawning time on the flagship devices and is only very
noticeable on lower-end devices with a weaker CPU and slower storage. The spawning
time impact only applies when the app doesn't already have an app process and the OS
will try to keep app processes cached in the background until memory pressure forces
it to start killing them.</p>
<p>In the typical Zygote model, a template app process is created during boot and
every app is spawned as a clone of it. This results in every app sharing the same
initial memory content and layout, including sharing secrets that are meant to be
randomized for each process. It saves time by reusing the initialization work. The
initial memory usage is reduced due to copy-on-write semantics resulting in memory
written only during initialization being shared between app processes.</p>
<p>The Zygote model weakens the security provided by features based on random secrets
including Address Space Layout Randomization (ASLR), stack canaries, heap canaries,
randomized heap layout and memory tags. It cripples these security features since
every app has the values for every other app and the values don't change for fresh app
processes until reboot. Much of the OS itself is implemented via non-user-facing apps
with privileges reserved for OS components. The Zygote template is reused across user
profiles, so it also provides a temporary set of device identifiers across profiles
for each boot via the shared randomized values.</p>
</section>
<section id="bugs-uncovered-by-security-features">
<h2><a href="#bugs-uncovered-by-security-features">Bugs uncovered by security features</a></h2>
<p>GrapheneOS substantially expands the standard mitigations for memory corruption
vulnerabilities. Some of these features are designed to directly catch the memory
corruption bugs either via an explicit check or memory protection and abort the
program in order to prevent them from being exploited. Other features mitigate issues
a bit less directly such as zeroing data immediately upon free, isolated memory
regions, heap randomization, etc. and can also lead to latent memory corruption bugs
crashing instead of the program continuing onwards with corrupted memory. This means
that many latent memory corruption bugs in apps are caught along with some in the OS
itself. These bugs are not caused by GrapheneOS, but rather already existed and are
uncovered by the features. The features are aimed at preventing or hindering exploits,
not finding bugs, but they do that as part of doing their actual job.</p>
<p>Similarly, some of the other privacy and security improvements reduce the access
available to applications and they may crash. Some of these features are always
enabled under the hood, while others like the Network and Sensors toggles are
controlled by users via opt-in or opt-out toggles. Apps may not handle having access
taken away like this, although it generally doesn't cause any issues as it's all
designed to be friendly to apps and fully compatible rather than killing the
application when it violates the rules.</p>
<p>If you run into an application aborting, try to come up with a process for
reproducing the issue and then capture a bug report via the 'Take bug report'
feature in Developer options. Report an issue to <a
href="https://github.com/GrapheneOS/os-issue-tracker/issues">the GrapheneOS OS
issue tracker</a> and email the bug report capture zip to contact@grapheneos.org
with the issue tracker number in the subject like "Bug report capture for issue
#104". The bug report capture includes plain text 'tombstones' with logs,
tracebacks, address space layout, register content and a tiny bit of context
from memory from areas that are interesting for debugging. This may contain
some sensitive data. Feel free to provide only the tombstone for the relevant
crash and filter out information you don't want to send. However, it will be
more difficult to debug if you provide less of the information. If the app
doesn't work with sensitive information, just send the whole tombstone.</p>
</section>
<section id="wifi-privacy">
<h2><a href="#wifi-privacy">Wi-Fi privacy</a></h2>
<p>Wi-Fi on GrapheneOS is very privacy-friendly and is essentially anonymous as long
as apps do not leak uniquely identifying information to the network. GrapheneOS avoids
allowing itself to be fingerprinted as GrapheneOS, other than connections which are
documented (see the FAQ) and can be easily disabled or forced through a VPN
service.</p>
<section id="wifi-privacy-scanning">
<h3><a href="#wifi-privacy-scanning">Scanning</a></h3>
<p>MAC randomization is always performed for Wi-Fi scanning. Pixel
phones have firmware support for scanning MAC randomization going
<a href="https://android-developers.googleblog.com/2017/04/changes-to-device-identifiers-in.html">significantly beyond a naive implementation</a>.
On many other devices, there are identifiers exposed by Wi-Fi scanning beyond the MAC
address such as the packet sequence number and assorted identifying information in the
probe requests.</p>
<p>Avoid using hidden APs (i.e. APs not broadcasting their SSID) since all
known hidden SSIDs end up being broadcast as part of scanning for networks to
find them again. SSIDs are not broadcast for standard non-hidden APs. Hidden
APs are only hidden when no devices are connected. It makes little sense as a
privacy feature, especially for a non-mobile AP where knowing the AP exists
can't be used for tracking it since it doesn't move. The feature reduces your
privacy rather than increasing it. If you need to use a hidden AP, make sure
to delete the saved network afterwards.</p>
<p>Wi-Fi and Bluetooth scanning for improving location detection are disabled by
default, unlike the stock OS. These can be toggled in Settings ➔ Location ➔ Wi-Fi and
Bluetooth scanning. These features enable scanning even when Wi-Fi or Bluetooth is
disabled, so these need to be kept disabled to fully disable the radios when Wi-Fi and
Bluetooth are disabled. GrapheneOS doesn't yet have an implementation of a coarse
location service to supplement GPS location, so enabling these options doesn't
actually do anything at the moment. Implementing a supplementary location service is
planned but we need a robust, secure and private implementation via a local database.
The initial focus will likely be a cell phone tower database, so these features still
wouldn't be relevant.</p>
</section>
<section id="wifi-privacy-associated">
<h3><a href="#wifi-privacy-associated">Associated with an Access Point (AP)</a></h3>
<p>Associated MAC randomization is performed by default. This can be controlled
per-network with Settings ➔ Network & Internet ➔ Wi-Fi ➔ <network> ➔
Advanced ➔ Privacy.</p>
<p>In the stock OS, the default is to use a unique persistent random MAC address for
each network. It has 2 options available: "Use randomized MAC (default)" and "Use
device MAC". In GrapheneOS, the default is generating a new random MAC address when
connecting to a network. It has 3 options available: "Use fully randomized MAC
(default)", "Use per-network randomized MAC" and "Use device MAC".</p>
<p>The DHCP client uses the anonymity profile rather than sending a hostname
so it doesn't compromise the privacy offered by MAC randomization. When the
per-connection MAC randomization added by GrapheneOS is being used, DHCP
client state is flushed before reconnecting to a network to avoid revealing
that it's likely the same device as before.</p>
<p>GrapheneOS also disables support for stable link-local IPv6 addresses, since these
have the potential to be used as identifiers. It's more sensible to use typical
link-local address generation based on the (randomized) MAC address since link-local
devices have access to both. As of Android 11, Android only uses stable link-local
privacy addresses when MAC randomization is disabled, so we no longer need to disable
the feature.</p>
</section>
</section>
<section id="lte-only-mode">
<h2><a href="#lte-only-mode">LTE-only mode</a></h2>
<p>If you have a reliable LTE connection from your carrier, you can reduce attack
surface by disabling 2G / 3G connectivity in Settings ➔ Network & Internet ➔
Mobile network ➔ Preferred network type. Traditional voice calls will only work in
the LTE-only mode if you have either an LTE connection and VoLTE (Voice over LTE)
support or a Wi-Fi connection and VoWi-Fi (Voice over Wi-Fi) support. VoLTE /
VoWi-Fi works on GrapheneOS for most carriers unless they restrict it to carrier
phones. US carriers other than T-Mobile tend to be missing these features due to
us not including their proprietary apps.</p>
<p>This feature is not intended to improve the confidentiality of traditional calls and
texts, but it might somewhat raise the bar for some forms of interception. It's not a
substitute for end-to-end encrypted calls / texts or even transport layer encryption.
LTE does provide basic network authentication / encryption, but it's for the network
itself. The intention of the LTE-only feature is only hardening against remote
exploitation by disabling an enormous amount of legacy code.</p>
</section>
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