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more information on identifiers

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Daniel Micay 2020-04-30 16:22:06 -04:00
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<a href="#non-hardware-identifiers">What about non-hardware identifiers?</a> <a href="#non-hardware-identifiers">What about non-hardware identifiers?</a>
</h3> </h3>
<p>In addition to not having a way to identify the hardware, apps cannot directly
identify the installation of the OS on the hardware. Apps only have a small portion of
the OS configuration exposed to them and there is not much for device owners to change
which could identify their installation. Apps can identify their own app installation
via their app data and can directly (until that's removed) or indirectly identify a
profile. Profiles should be used when separate identities are desired. Profiles can be
used as temporary ephemeral identifies by creating them for a specific need and then
deleting them. The rest of this answer only provides more technical details, so you
can stop reading here if you only want an overview and actionable advice (i.e. use
profiles as identities not inherently tied to each other).</p>
<p>Apps can generate their own 128-bit or larger random value and use that as an <p>Apps can generate their own 128-bit or larger random value and use that as an
identifier for the app installation. Apps can create data in their app-specific identifier for the app installation. Apps can create data in their app-specific
external storage directory by default without needing permission, and in the legacy external storage directory by default without needing permission, and in the legacy
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storage model, this data is automatically removed when the app is uninstalled. storage model, this data is automatically removed when the app is uninstalled.
GrapheneOS includes Seedvault as an OS backup service which must be explicitly GrapheneOS includes Seedvault as an OS backup service which must be explicitly
enabled, and it has the option to automatically restore app data when an app is enabled, and it has the option to automatically restore app data when an app is
reinstalled, which would avoid wiping this kind of data so the app wouldn't lose track reinstalled, so it wouldn't lose track of it being the same profile.</p>
of it being the same profile.</p>
<p>The <code>ANDROID_ID</code> string is a 64-bit random number represented as a hex <p>The <code>ANDROID_ID</code> string is a 64-bit random number, unique to each
encoded string, unique to each combination of profile and app signing key. The 64-bit combination of profile and app signing key. The 64-bit limitation means it isn't
limitation means it isn't particularly useful due to the possibility of collisions. particularly useful due to the possibility of collisions. It's tied to the lifetime of
It's tied to the lifetime of profiles and does not persist through profile deletion or profiles and does not persist through profile deletion or a factory reset. This is
a factory reset. This is comparable to an app targeting the legacy storage model comparable to an app targeting the legacy storage model storing a 64-bit random value
storing a 64-bit random value in the app-specific external storage directory. In the in the app-specific external storage directory. In the future, GrapheneOS will likely
future, GrapheneOS will likely change this to be tied to the lifetime of app change this to be tied to the lifetime of app installations rather than profiles. An
installations rather than profiles. Even then, profiles should be used when separate app could still track the identity of the profile through data you give it access to or
identities are desired. An app could still track the identity of the profile through via data another app chooses to share with them.</p>
data you give it access to or via data another app chooses to share with them.
Profiles can be used as temporary ephemeral identifies by creating them for a specific
need and then deleting them.</p>
<p>The advertising ID is a Google Play services feature not included in the baseline <p>The advertising ID is a Google Play services feature not included in the baseline
Android API, so it isn't an API included in GrapheneOS. The advertising ID is unique Android API, so it isn't an API included in GrapheneOS. The advertising ID is unique
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collisions, although a device messing with apps could set it to the same value used in collisions, although a device messing with apps could set it to the same value used in
another profile. The advertising ID is exposed via the Settings app and can be reset another profile. The advertising ID is exposed via the Settings app and can be reset
to a new random value, unlike <code>ANDROID_ID</code> which remains the same for the to a new random value, unlike <code>ANDROID_ID</code> which remains the same for the
lifetime of the profile.</p> lifetime of the profile, but apps can tie it the previous ID since they can detect
that it changed via their own ID in their app data.</p>
<p>Apps do not have access to user data by default and cannot ever access the data of <p>Apps do not have access to user data by default and cannot ever access the data of
other apps without those apps going out of the way to share it with them. If apps are other apps without those apps going out of the way to share it with them. If apps are