I write my blog in Hungarian, but a few entries are available in English, also via RSS


kr!pt - kript.berta.hu2020-10-17

I was looking for an encryption/decryption tool with a very simple GUI that is available on all platforms (including mobile phones) and uses an open format so that I can decrypt my file via other standard tools too. Another key requirement was that I had to trust the tool.

The main use case was the protection of those few files I do not want to upload to a cloud drive unencrypted.

Having checked and discarded multiple Android apps, I ended up writing a tool on my own. Please find it here:


It is just an HTML file with JavaScript, your browser runs it on the client side only, it does not upload anything anywhere. Actually, it is just a very simple wrapper for the CryptoJS library. Whatever I encrypt can be decrypted with an equivalent OpenSSL command. I used it on files ~10 megabytes, anything bigger should not be handled in a browser.

Feel free to use it! :)


What does the word 'cyber' mean?2020-05-31

One can meet the wore 'cyber' more and more frequently; sometimes as part of expressions like 'cybercrime', 'cyberattack' or 'cyberwar', but nowadays I hear people say that what really scares them is 'the cyber'. What does the word 'cyber' mean?

The word 'cyber' comes from cybernetics, an approach for controlling systems or processes with feedback loops. Such a system can be a turbine but can also be a social or economic process. The word cybernetics was created in the 1940s and it is older than IT.

The sci-fi author William Gibson envisioned in the 1980s a bleak, dystopic world in his books Neuromancer, Count Zero and Mona Lisa Overdrive, where the world with a wide-spread overarching computer network called cyberspace. In Gibson's books, information is the most valuable asset; the world is controlled by multinational corporations more powerful than nation states. Humanity is struggling, decimated by epidemics, war and pollution, but gadgets are part of the everyday life (or even people's bodies), and people tend to spend more and more of their lives in cyberspace. Cyberspace is where business is done, wars are waged and there is also crime in cyberspace. There are also cyberspace cowboys (known as hackers today), people who know cyberspace very well and try to get along as criminals, mercenaries, investigators, bodyguards or anything else in between. Gibson is one of the founders of the 'cyberpunk' genre.

A sci-fi expression has gone out of control and mainstream, as if we could read in today's news about Jedi, Bene Gesserit or muggles.

The word 'cyber' typically means that something is done via IT, via computer networks or via the Internet. It is often used in a negative context (e.g. about attacks), but it has no negative meaning by itself. Meanwhile, for IT people everything is cyber. Technically, if you remove the word 'cyber' from a sentence, it rarely changes its meaning. The word 'cyber' has become yet another empty marketing buzzword, meaning that somebody is trying to sell you something.

TL;DR: s/cyber//gi


animation: agile vs waterfall2019-02-02

I created a PowerPoint animation on the comparing agile and waterfall software development featuring Fred Flintstone.


Our crypto course at AIT2015-03-22

Together with Levente Buttyán (Crysys Lab) and István Lám (Tresorit) we run a course called Applied Cryptography at Aquincum Institute of Technology. AIT is a faculty of the Budapest University of Technology and Economics (BME), offering a study abroad program for North American students.

Our course introduces students to building blocks of cryptography (primitives), provides an overview of PKI and electronic signatures shows crypto protocols for secure communications and how crypto can be used in cloud services. While providing mathematical background, the course focuses on how crypto can be used - covering its technical, business, management and legal aspects. I am holding the lectures about PKI and electronic signatures.

Please find further details and my slides here.


My presentation at Cryptonite2014-09-01

Previously I blogged about a lecture series in cryptography called Cryptonite, this is an initiative of Hackerspace Budapest. Last week I gave a presentation at Cryptonite, I spoke about following two topics:

My slides are in English, but I spoke in Hungarian.

Update: Please find a video of my presentation here.


More entries...


This is my personal website, opinions expressed here are strictly my own, and do not reflect the opinion of my employer. My English blog is experimental and only a small portion of my Hungarian blog is available in English. Contents of my blog may be freely used according to Creative Commons license CC BY.