Gernot Walzl


Android is the most popular operating system for mobile phones and tablets.


Most vendors have their own (slightly modified) distribution of Android.
Some distributions do not allow the user to remove preinstalled apps.
Luckily, there are devices available that support flashing alternative Android distributions.

Successor of CyanogenMod
Supported devices:

As in 2020, there are approximately three million apps on Google Play.
If you need an app for something, you are possibly trying out some of them.
Some of them need access to personal data. Some of them are full of advertisements.
Here is a list of apps, I can recommend.

Available on F-Droid

App store with free and open source software (foss)
Internet browser based on Firefox
K-9 Mail
Full-featured email client
Offline/online maps and navigation
Document Viewer
Successor of EBookDroid
Lightweight YouTube front-end
Barcode Scanner
QR code scanner
Graph 89
Calculator emulator
Live wallpaper of famous art
Change Detection
Automatically detects changes on websites
Etar - OpenSource Calendar
Supports offline calendars
Calendar Import-Export
Import & export (backup) calendars using ics files
Export Contacts
Backup contacts in vCard 3.0 contacts file (*.vcf)
Terminal emulation
Terminal toolbar can be hidden by pressing volume up and q.
Command line access to device API
Version 0.31 is the last that supports sending sms messages.
To install old versions, the F-Droid Archive repository needs to be enabled.
Hacker's Keyboard
Keyboard with tab, ctrl and arrow keys

Available on

City navigation

Verify Signature of Packages

Android packages (APKs) are signed with self-signed certificates.

The command line tool apksigner is part of the Android SDK Build Tools.

In Termux, apksigner can be installed using the following command:
pkg install apksigner

To verify the signature of an APK, execute the following command:
apksigner verify --print-certs org.fdroid.fdroid_1010000.apk

Signer #1 certificate DN: CN=Ciaran Gultnieks, OU=Unknown, O=Unknown, L=Wetherby, ST=Unknown, C=UK
Signer #1 certificate SHA-256 digest: 43238d512c1e5eb2d6569f4a3afbf5523418b82e0a3ed1552770abb9a9c9ccab
Signer #1 certificate SHA-1 digest: 05f2e65928088981b317fc9a6dbfe04b0fa13b4e
Signer #1 certificate MD5 digest: 17c55c628056e193e95644e989792786
Signer #1 certificate DN: CN=CodeSigning for HERE Global BV, OU=Android Signing, OU=Android Signing, O=HERE Global BV, L=Veldhoven, ST=Veldhoven, C=NL
Signer #1 certificate SHA-256 digest: f3fa1a6eb3f8bace3662e83ab167a90462d1a78240e64cf24675887c5d78cb13
Signer #1 certificate SHA-1 digest: 6d256640c0eff26ccb3a8b817cdc901f3d1d77b4
Signer #1 certificate MD5 digest: 528eab01b512151498f89f5e88767bf9
Tor Browser
Signer #1 certificate DN: C=US, ST=WA, L=Seattle, O=The Tor Project, CN=Tor Browser
Signer #1 certificate SHA-256 digest: 20061f045e737c67375c17794cfedb436a03cec6bacb7cb9f96642205ca2cec8
Signer #1 certificate SHA-1 digest: 6e9d890dcf0d5ca0d7c8f28c822ed228da5f3490
Signer #1 certificate MD5 digest: e8ee59c262de3d867b015afbae38e061

Send SMS Messages

Using Termux:API

termux-sms-send -n "+1234567890" "Just a test!"

Using ADB

adb shell service call isms 7 i32 0 s16 "" s16 "+1234567890" s16 "null" s16 "Just a test!" s16 "null" s16 "null"

Privacy Firendly Apps
Dominik Schürmann
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