Open source security/privacy focused AOSP rom
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This is an effort to produce an AOSP based Android ROM with only the minimum binary blobs in order for all hardware to function.

Additionally, we seek to produce signed deterministic builds allowing for high accountability via redundant CI systems all getting the same hash.

Heavily inspired by the former CopperheadOS (RIP) project. We seek to provide a trustable path to free public AOSP builds patched for privacy and security.


Public releases are pending sustainable/automated CI/CD work to do reproducible builds and multisig.

Testing is currently manual. "True" implies only all hardware and surface level functionality appears to work. E2E testing integration is WIP

Testers, builders, and hosting bandwidth needed.


Please join us on IRC: ircs://!os



  • 100% Open Source and auditable
    • Except for mandatory vendor blobs hash verified from Google Servers
  • Minimal changes to stock AOSP functionality
  • Automated build system:
    • Completely run inside Docker for portability
    • Customize builds from central config file.
    • Automatically pin hashes from upstreams for reproducibility
    • Automated patching/inclusion of upstream Android Sources
  • Removed:
    • Google Play Services
    • Proprietary system apps
    • OMA-DM backdoors
    • Browser2 - Mostly unmaintained
    • Webview - Mostly unmaintained
    • Calendar - Mostly unmaintained
    • Quicksearch - Requires Google Play Services. Also removed from Launcher.
  • Added:
    • Custom Android Verified Boot included in factory images
    • F-Droid - Trusted as system app without need to enable "Unknown Sources"
    • Chromium - With several privacy/security patches
    • Backup - Minor OS changes made to allow backing up any app
    • Updater - Patched to use update server


  1. Reproducible builds
    • Allow third parties to prove a build came from expected open source code.
  2. Verified Builds
    • Test builds signed with test keys are automated and used for verification.
    • Third party verifiers will maintain webhook activated build nodes
      • Will be in different legal jurisdictions
      • should have a public reputation to lose if they tamper a build
      • can offer mirrors signed with their own keys
      • will publish signatures for test builds to be in 'verified' channel
    • Updater app will verify signatures from m-of-n builders (e.g 2 of 3)
    • Ability to build/sign/update own releases via Terraform automation
  3. Compatibility Test Suite
    • Every device should have a sponsor with an automated CTS test station
  4. Hardening
    • Test and integrate Android Hardening Project patches
      • Hardened Memory Allocator
      • Chromium security/privacy patches
      • Various platform patches for better permissions controls
    • BadUSB
      • Setup global settings option to toggle USB OTG support
      • Disable all USB devices by default
    • Allow build options to disable hardware as needed for airgap setups.
  5. Remote Attestation
    • Auditor app integration
      • -if- @thestinger can be convinced to open source it
      • He is seeking compensation for his time creating it. Make An Offer
  6. Two Factor Authentication
    • Replace proprietary Google Play Services U2F with open/auditable one.
  7. Accessibility
    • Global Dark Mode
    • One Handed Mode
  8. Fluff
    • Wallpaper/boot animation
    • Support channel link on home screen
    • Support flashing from windows for confused people we take pity on


Device Codename Tested Verifiable Secure Boot Download
Pixel 3 XL Crosshatch TRUE FALSE AVB 2.0 Soon™
Pixel 3 Blueline FALSE FALSE AVB 2.0 Soon™
Pixel 2 XL Taimen TRUE FALSE AVB 1.0 Soon™
Pixel 2 Walleye FALSE FALSE AVB 1.0 Soon™
Pixel XL Marlin TRUE FALSE dm-verity Soon™
Pixel Sailfish TRUE FALSE dm-verity Soon™

Release hosting is sponsored by JFrog




cd crosshatch-PQ1A.181205.006/


Unlock the bootloader.

NOTE: You'll have to be in developer mode and enable OEM unlocking

adb reboot bootloader
fastboot flashing unlock

Once the bootloader is unlocked it will wipe the phone and you'll have to do basic setup to be able to drop into fastboot. You can skip everything since you'll be starting from scratch again after flashing #!OS

Reboot phone in fastboot and flash


adb reboot bootloader

Pixel 2+

adb reboot fastboot



  • Linux host system
  • Docker
  • x86_64 CPU
  • 10GB+ available memory
  • 60GB+ disk

Generate Signing Keys

Each device needs its own set of keys:

make DEVICE=crosshatch keys

Build Factory Image

Build flashable images for desired device:

make DEVICE=crosshatch clean build release



Clean everything but keys

make mrproper


Build a given device twice from scratch and compare with diffoscope:

make shell


Create a shell inside the docker environment:

make shell


Output all untracked changes in android sources to a patchfile:

make diff > patches/my-feature.patch


adb reboot fastboot
make install




Build latest config from upstream sources:

make DEVICE=crosshatch config manifest


Who is this project for?

Individuals that desire a device that favors privacy and security over easy access to proprietary software and services.

Wait can I not run -Insert-App-Here-

You technically can download/install most apps in the Play store but we of course can't recommend that. Some apps that have a hard requirement on Google Play Services can be tricked with [MicroG][mg] but this increases attack surface and though it will probably work in many cases, this is not supported or recommended.

Yalp store is an open source browser for Google Play Store and is available on F-Droid.

Also see "Alternatives" below to find alternatives for popular apps.

Why is -Insert-Device-Here- not supported?

Most vendors don't release sources and tooling to reproduce their builds or do so with substantial delays. Many vendors even disable critical security features they don't understand and allow various Supply Chain Attacks. These are a headache to reverse engineer, test, audit, patch, and generally maintain.

Unless a vendor decides to produce source repos with at least the quality of AOSP we will only support AOSP supported devices which today means the Pixel series of mobile handsets.

Pixel devices start at $100-200 and we will try to maintain support for at least one device at this price point to keep the project accessible.

Why not use LineageOS, AOKP, or insert-project-here ?

As of the time of this writing most popular ROMs are virtually unusuable without Google Play Services and the proprietary parts of android. They also tend to make changes that make taking upstream source code time consuming thus often delaying security updates.

Secondly virtually all roms sign using "test" keys, leaving all of them vulnerable to Evil Maid Attacks and thus worse-off security wise than stock Android.

Third, builds are almost never easily reproducible if at all meaning that a single coerced maintainer could slip in a subtle flaw without very little chance of detection

Lastly, they almost all source binaries from sketchy locations like the infamous "TheMuppets" repo which an unknown number of people have push access to. This sort of activity acts as a security SPOF for popular roms.

Why should anyone trust this project?

Trust, but Verify. While we may be upstanding people today, we might be coerced tomorrow by a state actor that wants access to the device in your pocket. You can run our reproducible build systems yourself and sound the alarm if the builds we produce don't line up with the published source code.

The more people that verify, the less reason a bad actor has to try to attack maintainers. Maintaining a system that requires zero trust on the maintainers is a core part of our plan to be resistant to Australia-style strongarm backdoor requests.


Giving up Google Play services and stock proprietary applications is a big ask for a lot of people that have grown to rely on particular apps for their lifestyle.

To address this consider looking at some of the below alternatives for popular applications.

Some things won't have alternatives and in those cases you will have to decide to sideload a specific proprietary APK via Yalp Store or live without that app.

You may also find popular travel apps like Kayak, Uber ans Lyft have very usable mobile webapps you can pin to your desktop for a similar experience to a native app.

App Alternative(s) Notes
Chrome Chromium, OrFox Chromium is built-in to #!os
Play F-Droid, Yalp F-Droid is built-in to #!oa
GMail K9Mail
Drive Nextcloud
Music D-Sub Will need a Subsonic capable server
Maps OsmAnd~
Auth. Yubico Auth.
Hangouts Weechat,
Voice Ring
Youtube NewPipe, SkyTube


Use at your own risk. You might be eaten by a grue.