computer science

OpenKeychain

OpenKeychain is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand OpenKeychain rather than just read about it. In short: OpenKeychain is a free and open-source mobile app for the Android operating system that provides strong, user-based encryption which is compatible with the OpenPGP standard. This allows users to encrypt, decrypt, sign, and verify signatures for text, emails, and files.

Key takeaways

OpenKeychain belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect OpenKeychain to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of OpenKeychain from memory before moving on to harder problems.

Reference excerpt

OpenKeychain is a free and open-source mobile app for the Android operating system that provides strong, user-based encryption which is compatible with the OpenPGP standard. This allows users to encrypt, decrypt, sign, and verify signatures for text, emails, and files. The app allows the user to store the public keys of other users with whom they interact, and to encrypt files such that only a specified user can decrypt them. In the same manner, if a file is received from another user and its public keys are saved, the receiver can verify the authenticity of that file and decrypt it if necessary.

K-9 Mail Support Together with K-9 Mail, it supports end-to-end encrypted emails via the OpenPGP INLINE and PGP/MIME formats. The developers of OpenKeychain and K-9 Mail are trying to change the way user interfaces for email encryption are designed. They propose to remove the ability to create encrypted-only emails and hide the case of signed-only emails. Instead, they focus on end-to-end security that provides confidentiality and authenticity by always encrypting and signing emails together.

Reception OpenKeychain is listed on the official OpenPGP homepage and the well-known developer collective Guardian Project recommends it instead of APG to encrypt emails. TechRepublic published an article about it and conclude that "OpenKeychain happens to be one of the easiest encryption tools available for Android (that also happens to best follow OpenPGP standards)." The publisher Heise reviewed it in their c't Android magazine 2016 and discussed OpenKeychain's backup mechanism. The academic community uses OpenKeychain for experimental evaluations: It has been used as an example where cryptographic operations could be executed in a Trusted Execution Environment. Furthermore, modern alternatives for public key fingerprints have been implemented by other researchers. In 2016, the German Federal Office for Information Security published a study about OpenPGP on Android and evaluated OpenKeychain's functionality. OpenKeychain has been adapted to work with smartcards and NFC rings resulting in a usability study published on Ubicomp 2017.

Funding The OpenKeychain developers participated in 3 Google Summer of Code programs with a total of 6 successful students. In 2015, one of the main developers got a one-year funding to improve the OpenPGP support in K-9 Mail paid by the Open Technology Fund.

History OpenKeychain has been created as a fork of Android Privacy Guard (APG) in March 2012. Between December 2010 and October 2013 no new version of APG was released. Thus, OpenKeychain has been started with the intention of picking up the development to improve the user interface and API. A first version 2.0 has been released in January 2013. After three years without updates, APG merged back security fixes from OpenKeychain and some months later rebased an entire new version on OpenKeychain’s source code. However, this process stopped in March 2014, while the OpenKeychain developers continued to regularly release new versions. A number of vulnerabilities found by Cure53 have been fixed in OpenKeychain. These are still not fixed in APG since its last release in March 2014. Since K-9 Mail version 5.200, APG is no longer supported as a cryptography provider.

Maintenance Mode Since 17 Aug 2021 OpenKeychain has been placed in "Maintenance Mode", because the maintainers have concluded that providing the features of OpenKeychain as an App, as opposed to a library, was a misguided decision in the first place. They continued to provide security fixes, but have become less responsive over time. Applications have started to switch to the Pgppainless library.

References

External links Official website GitHub repository of OpenKeychain OpenKeychain on Google Play OpenKeychain Android package at the F-Droid repository PGPainless - Use OpenPGP Painlessly!

Worked examples

Example 1 — a first encounter with OpenKeychain

Start with the simplest possible case. Write down what OpenKeychain claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to OpenKeychain before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about OpenKeychain ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of OpenKeychain

In research: OpenKeychain appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses OpenKeychain in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: OpenKeychain is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cryptographic software, Free and open-source Android software, OpenPGP, so understanding it makes those chapters shorter.
In everyday life: Look for OpenKeychain outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study OpenKeychain in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what OpenKeychain means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain OpenKeychain out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is OpenKeychain in simple terms?

Why does OpenKeychain matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study OpenKeychain?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on OpenKeychain.