How Kullo uses OpenSSL

Although Kullo uses the crypto library Botan for all it’s encryption jobs it needs OpenSSL. That is because The Open Kullo Protocol is an HTTP-based API that enforces TLS. Since we don’t want to reinvent the wheel and implement HTTPs on our own, we use a library for that. On the desktop platforms that is Qt Network at the moment. An alternative would be cURL and I am sure there are others. These libraries have in common that they depend on OpenSSL to implement the TLS. If there’s an Botan TLS based HTTP(s)-library for C++ out there, I’d appreciate a hint in the comments.

So OpenSSL is mandatory. But where do we get it from and in which version? That question has to be answered differently for every operating system. Continue reading

Kullo goes live

We’re happy to announce that we’re launching Kullo publicly today. From now on, everyone can register a Kullo address without any registration code whatsoever. This is a major step on our journey to make secure communication possible for everyone.

Sending end-to-end encrypted messages and documents is now as easy as Skype. Simply download the software, choose a Kullo address and get started.


You don’t have a Kullo address yet? Get it now at

Workaround for OS X update bug in Kullo 0.20.9

In Kullo 0.20.9, which was released on Monday this week (2015-01-27), there is a bug that prevents a user to interact with the app entirely under some conditions.

The problem appears when all of these conditions are fulfilled:

  • User runs OS X
  • MasterKey backup reminder pops up
  • A Kullo update is available

In this case you see one of the windows but you are not able to click any button or close Kullo. Continue reading

Introducing todo mode

From the very beginning, every Kullo message had the two message states: read/unread and done/undone. That is a result of the common problem with email: You read a message on your phone but right now you’re not able to get it done. Nevertheless, it is marked as read and gets easily lost when you open your inbox at your desktop later.

todo-buttonTo make working with done/undone more useful, we finished the todo mode in the 0.20.9 release. You can now filter messages as well as conversations for those that need to be done. Just use the little todo mode button to activate todo mode. Powerusers just hit Cmd+T on OS X and Ctrl+T on other platforms. Continue reading

Kullo 20


Kullo 20 is our next chapter to make secure communication even more convenient and fun. We did not only fix a huge list of minor bugs but also implemented a number of features, our early users asked for, including:

  • Group conversations
  • Inline previews of image attachments
  • Improved security for read/done flag
  • German translation
  • Signed code to reduce warnings on OS X and Windows
  • In-app downloader for updates

The update will be online after lunch today for existing Kullo users. If you don’t have a Kullo address yet, make sure to subscribe on out waiting list.