A5/1 cracker accelerated with OpenCL


SDR software that sucks less

OpenWRT hacking

OpenWRT and Debian crossarch fun

My articles

AbcLinuxu (Czech) - Linux, OpenSource, security (Czech) - Bitcoin, computer security

KP (Czech) - civil rights advocacy

My talks

Fast attacks on A5/1 at InstallFest 2016 (Czech)

Software defined radio at InstallFest 2016 (Czech)

Build your own NSA! (English) + recording (Czech) at CTJB 2014

brmlab tour (photos) + recording (Czech) at CTJB 2014

Bitcoin at LinuxDays 2012 and CryptoFest 2013 + recording (Czech)

Talknight (Czech)

Misc. user page - lots of useful tips and code snippets

Videoserver - recordings of various lectures

More code!






List of brmlab projects I contribute to

Some commercial experience…

▒ Linux administration (mail, web server, Samba, calendar, network…) in several small companies and ISP

▒ Some websites (no, I don't do the design itself), custom CMS, Wordpress, Prestashop

▒ A SCADA controller with advanced realtime FPGA-based motor control

▒ BT4LE distributed data acquisition for patient monitoring at Mindpax

▒ midibtn - device with lots of buttons and colorful lights with MIDI interface

FSB, a time synchronization device for FSV ČVUT drone



GSM sniffing and decoding toolkit


realtime the entire Tetra network!


decode metadata and maybe more


I work as a Linux administrator, webmaster and embedded developer (AVR, RPi, some circuit and board design and a very basic knowledge of FPGA). I have proven that I can quickly introduce myself into almost any programming language or technology and produce drafts of seemingly impossible things. However, I'm not very good at extending products beyond advanced prototypes - but people learned it and are hiring me for rapid prototyping, which I really enjoy!

I am currently studying 3rd year of bachelor program General Computer Science on Charles University full-time, so I have very limited time for other projects.

OpenPGP key, fingerprint CD98 5440 4372 0C6D 164D A24D F019 2F8E 6527 282E.

  • E-mail: jenda .a. hrach ... eu
  • Jabber: hrachj .a. abclinuxu ... cz, hrachj .a. jabber ... cz
  • IRC: Jenda` on #brmlab on freenode
  • Bitcoin: 1JENDAF7MncjqE3nPA1Zzqh85WJhvdpSwX
  • HAM: OK1DNA in JO70FB (sometimes idling on OK0N, but not really often)
  • IČ (czech tax identification number): 887 88 954
  • Phone: +420 737 660 630. Please note that phone eavesdropping is a common practice in my country. Additionaly, as location data are routinely sold by Czech operators, I often leave my phone at home.
  • SIP (usually offline): 910114502,