Building a Signing Server

The Android APK signing model sets the expectation that the signing key will be the same for the entire lifetime of the app. That can be seen in the recommended lifetype of an Android signing key: 20+ years. On top of that, it is difficult to migrate an app to a new key. Since the signing key is an essential part to preventing APKs from impersonating another, Android signing keys must be kept safe for the entire life of the app. [Read More]

Repomaker Usability Trainers Worldwide, June 2017

Repomaker Usability, Trainers Worldwide Study Prepared by Carrie Winfrey and Tiffany Robertson, Okthanks, in partnership with F-Droid and Guardian Project OK Thanks – Guardian Project For more information, contact carrie@okthanks.com. Purpose The purpose of this study was to understand the following things. Are users able to complete basic tasks including, creating a repo, adding apps from other repos, removing apps, editing app details, and creating a second repo? [Read More]

Tracking usage without tracking people

One thing that has become very clear over the past years is that there is a lot of value in data about people. Of course, the most well known examples these days are advertising and spy agencies, but tracking data is useful for many more things. For example, when trying to build software that is intuitive and easy to use, having real data about how people are using the software can make a massive difference when developers and designers are working on improving their software. [Read More]

fdroidserver UX Testing Report

We ran user tests of fdroidserver, the tools for developers to create and manage F-Droid repositories of apps and media. This test was set up to gather usability feedback about the tools themselves and the related documentation. These tests were put together and run by Seamus Tuohy/Prudent Innovation. Methodology Participants completed a pretest demographic/background information questionnaire. The facilitator then explained that the amount of time taken to complete the test task will be measured and that exploratory behavior within the app should take place after the tasks are completed. [Read More]

Announcing new libraries: F-Droid Update Channels

In many places in the world, it is very common to find Android apps via a multitude of sources: third party app stores, Bluetooth transfers, swapping SD cards, or directly downloaded from websites. As developers, we want to make sure that our users get secure and timely update no matter how they got our apps. We still recommend that people get apps from trusted sources like F-Droid or Google Play. [Read More]

New research report on the challenges developers face

The Guardian Project has been working with the F-Droid community to make it a secure, streamlined, and verifiable app distribution channel for high-risk environments. While doing this we have started to become more aware of the challenges and risks facing software developers who build software in closed and closing spaces around the world. There are a wealth of resources available on how to support and collaborate with high-risk users. [Read More]

F-Droid User Testing, Round 2

#by Hailey Still and Carrie Winfrey **** Here we outline the User Testing process and plan for the F-Droid app store for Android. The key aims of F-Droid are to provide users with a) a comprehensive catalogue of open-source apps, as well as b) provide users with the the ability to transfer any app from their phone to someone in close physical proximity. With this User Test, we are hoping to gain insights into where the product design is successful and what aspects need to be further improved. [Read More]

F-Droid: A new UX 6 years in the making

_(post by Peter Serwylo)_ F-Droid has been a part of the Android ecosystem for over 6 years now. Since then, over 2000 apps have been built for the main repository, many great features have been added, the client has been translated into over 40 different languages, and much more. However, the F-Droid UX has never changed much from the original three tab layout: This will change with the coming release of F-Droid client v0. [Read More]

F-Droid Lubbock Report – What We Want to Know

F-Droid LBK Usability Study Report – What We Want to Know Prepared by Carrie Winfrey Preliminary Version – April 17, 2017 Introduction When planning this user test, the team outlined features and flows within the app on which we wanted feedback. From there, we created tasks for participants to complete that would access these areas, and produce insights related to our inquires. This document is organized by the tasks participants completed. [Read More]

Build Android apps with Debian: apt install android-sdk


In Debian stretch, the upcoming new release, it is now possible to build Android apps using only packages from Debian. This will provide all of the tools needed to build an Android app targeting the “platform” android-23 using the SDK build-tools 24.0.0. Those two are the only versions of “platform” and “build-tools” currently in Debian, but it is possible to use the Google binaries by installing them into /usr/lib/android-sdk.

[Read More]

F-Droid now supports APK Expansion Files aka OBB

Many games, mapping, and other apps require a large amount of data to work. The APK file of an Android app is limited to 100MB in size, yet it is common for a single country map file to be well over 100MB. Also, in order to get users running as quickly as possible, they should not have to wait for huge amounts of data to download in order to just start the app for the first time. [Read More]

Build Your Own App Store: Android Media Distribution for Everyone

Most people get their Android apps from Google Play. It is usually the simplest and most secure option for them. But there are also many people who do not have access to Google Play. This might be due to lack of a proper internet connection or simply because Google Play is blocked within their country. The F-Droid project already offers tools to create independent app distribution channels for Android apps. [Read More]

Imagining the challenges of developers in repressive environments

The Guardian Project team spends a lot of time thinking about users. In our work we focus on easy-to-use applications for users in high-risk scenarios. Because of this we are very focused on security. In our current work with the FDroid community to make it a secure, streamlined, and verifiable app distribution channel for high-risk environments we have started to become more aware of the challenges and risks facing software developers who build software in high-risk environments. [Read More]

Building the most private app store

App stores can work well without any tracking at all Attackers are increasingly seeing app stores as a prime attack vector, whether it is aimed at the masses like XCodeGhost or very targeted like in FBI vs Apple. When we install software from an app store, we are placing a lot of trust in a lot of different parties involved in getting the source code from the original developer delivered to our device in a useful form. [Read More]

How to Migrate Your Android App’s Signing Key

It is time to update to a stronger signing key for your Android app! The old default RSA 1024-bit key is weak and officially deprecated. What? The Android OS requires that every application installed be signed by a digital key. The purpose behind this signature is to identify the author of the application, allow this author and this author alone to make updates to the app, as well as provide a mechanism to establish inter-application trust. [Read More]

First Reproducible Builds Summit

I was just in Athens for the “Reproducible Builds Summit“, an Aspiration-run meeting focused on the issues of getting all software builds to be reproducible. This means that anyone starting with the same source code can build the exact same binary, bit-for-bit. At first glance, it sounds like this horrible, arcane detail, which it is really. But it provides tons on real benefits that can save lots of time. And in terms of programming, it can actually be quite fun, like doing a puzzle or sudoku, since there is a very clear point where you have “won”. [Read More]

CipherKit reproducible builds

We have been on a kick recently with making our build process support “reproducible builds” aka “deterministic builds”. What is this reproducible thing? Basically, what that means is that you can run a script and end up with the exact same binary file as our official releases, be it a APK, JAR, AAR, whatever. That lets anyone verify that our releases are produced only from the source in git, without including anything else, whether deliberately or accidentally (like malware). [Read More]

Building a trustworthy app store that respects privacy

One core piece of our approach is thinking about very high risk situations, like Ai Weiwei or Edward Snowden, then making the tools for operating under that pressure as easy to use as possible. That means that we might occasionally come across as a little paranoid. It is important to dive into the depths of what might be possible. That is an essential step in evaluating what the risks and defenses are, and how to prioritize them. [Read More]

Getting Android tools into Debian

As part of Debian’s project in Google Summer of Code, I’ll be working with two students, Kai-Chung Yan and Komal Sukhani, and another mentor from the Debian Java Team team, Markus Koschany. We are going to be working on getting the Android SDK and tools into Debian, as part of the Debian Android Tools team, building upon the existing work already included from the Java and Android Tools teams. [Read More]

Phishing for developers

I recently received a very interesting phishing email directed at developers with apps in Google Play. One open question is, how targeted it was: did anyone else get this? It turns out that Google has been recently stepping up enforcement of certain terms, so it looks like some people are taking advantage of that. It is a pretty sophisticated or manually targeted phishing email since they got the name of the app, email address, and project name all correct. [Read More]