The release of CalyxOS 7.2.2.0 is now available, developing the firmware based on the Android platform, free from ties to Google services, and offering additional tools for ensuring privacy and security. CalyxOS 7.2.2.0 has become the first stable release after the suspension of updates last August, which was caused by the need to overhaul the release formulation process, conduct a full audit, and change cryptographic keys following the departure of the project founder and technical leader, who had access to the digital signature keys. The new release is based on Android 16 and is available in builds for Pixel devices 4-9, Fairphone 4/5, Motorola Moto G32-G84, and SHIFTphone 8.
Instead of Google services, CalyxOS offers a suite of microG with an alternative implementation of the Google Play API, Google Cloud Messaging, and Google Maps, requiring no proprietary Google components. A layer utilizing Position or BeaconDB services is used instead of Google Network Location Provider for determining locations via Wi-Fi and cell towers. Nominatim from the OpenStreetMap project is used for address conversion to location (Geocoding Service).
Access to the network is managed using the Datura firewall, which allows restricting network access based on individual applications, connection methods (Wi-Fi, mobile network, VPN), and activity (for example, access can be denied to apps running in the background). There is an interface for monitoring application permissions. By default, the Calyx Chromium browser with the DuckDuckGo search engine is used, while the Tor Browser is available as an option. For app installations, F-Droid and Aurora Store (an alternative anonymous client for Google Play) are offered.
Other features of CalyxOS:
- A privacy-oriented calling interface with built-in capability to make calls through Signal and WhatsApp messengers using end-to-end encryption. Confidential phone numbers such as hotlines are hidden from the call log.
- By default, unknown USB devices are blocked.
- A function to disable Wi-Fi, Bluetooth, microphone, and camera after a certain period of inactivity.
- Network access lockdown mode for newly installed applications.
- The ability to use profiles to separate work and personal activities with data and application isolation between profiles.
- Integrated VPN support with pre-installed applications for Tor and Riseup. Capability to use the phone in hotspot mode (USB or Wi-Fi) with traffic routed through VPN or Tor.
- Verification of the system through digital signatures to protect against firmware spoofing or malicious alterations.
- Automatic monthly delivery of updates via OTA (over-the-air).
- Panic button for emergency data wipe and removal of specific applications.
- Automated application backup system that allows backups to be saved on a USB drive or in the Nextcloud cloud storage with client-side encryption.
- Using CoMaps for map navigation, OnionShare for file sharing, and Thunderbird for email.
Among the changes in the new release, in addition to upgrading to Android 16, support for the SHIFTphone 8 smartphone has been implemented, and versions of built-in applications have been updated. The builds are certified with a digital signature based on a new private key stored in a reworked infrastructure utilizing a Hardware Security Module (HSM), which has passed security audits and is not controlled by individual participants. Plans include the resumption of regular correction OTA updates and the release of CalyxOS 8 based on Android 17.
The new infrastructure for certifying firmware with a digital signature has been built to prevent dependence on individual participants and to protect against key leakage in case of system compromises. The YubiHSM 2 USB token was selected as the HSM module for hardware key storage and performing digital signature operations without extracting the keys. Since each supported device and firmware component requires a separate key for generating a digital signature, and all keys cannot fit into the YubiHSM 2 USB token, a multi-layer encryption was implemented — only the base primary key (wrap key) is constantly stored in the HSM, while the keys for creating digital signatures are stored outside the HSM in a form encrypted with the primary key. When creating a digital signature, the necessary encrypted external key is loaded into the HSM, decrypted with the primary key inside the HSM, and used for forming signatures without extracting keys from the HSM using tooling that supports the PKCS#11 standard (apksigner, signapk, and OpenSSL).
A new computer purchased from a randomly selected store was used to generate the primary private key, create a backup, and write the key into the HSM. Without an internet connection, a distribution of Tails was booted in live mode from a previously verified DVD disk on the computer, from which two YubiHSM 2 USB tokens (main and backup) were set up and initialized. Additionally, a copy of the key was created using Shamir's secret sharing scheme, splitting the key into 5 parts and distributing them among 5 trusted individuals (a minimum of 3 parts must be gathered to recover the key in case the USB tokens fail).
Source: opennet.ru
