About Harald Welte

About Harald

Who is Harald Welte? Well, that's what this website is all about.

I'm an independent, free-thinking, freedom-loving individual. I'm a workaholic, humanist and idealist.

Those who know me is that I don't really work for the money, but because a topic is exciting, or if there is some higher goal that can be achieved. I'd rather drop the most lucrative contract and instead work on something exciting and/or revolutionary.

My journey into technology and Free Software

I've been interested in technology ever since I can think of. According to my parents, as a toddler I learned to stand up just so I could reach the buttons of my fathers' stereo system. Things have gone downhill ever since.

From about 1990 onwards, long before the Internet was known to most people and before the web has even been invented, I was involved in data communications and the BBS community, participating in the message-based networks at the time, including Z-Netz, FIDO, TrekNet, CL, MAUS - and subsequently also participating in the UseNet.

To me, it was never just about using the technology, but about operating it, understanding it, and even modifying/improving or developing it. So first I was CoSysOp of a local BBS, but later moved to operate my own infrastructure with dial-in available for users and friends.

In terms of computers I've always mostly been on the PC/x86 side, starting from my very fist own 80286 with 16MHz, 1MB RAM and 20 MByte RLL Hard Disk. After some time with DR-DOS, GEO and the first incarnations of Windows (up to 3.11), I discovered Linux and never turned back ever since.

By about 1994 I was running my own small computer network at home, connected to the outside world via Modems, ISDN and even an analog leased line (38.4kbps) to have always-on connectivity and access to things like e-mail, newsgroups and IRC long before most people had ever heard of the internet. As part of my interest in the world of computer networks, I used to volunteer for KNF, a NGO that enabled internet access to individuals. That's where I got experience with technologies like OSPF, running an Usenet news server (inn), cyrus IMAP server, the smail MTA, Taylor UUCP, dial-up infrastructure, leased-line technology (analog, ISDN, PDH), ISDN PRI/BRI, etc.

At daytime, I was busy with my training as radio communications electronics technician, and in my spare time I was working with much more exiting technology ;)

In the late 1990ies the Internet boom reached Germany, and people with skills in that area were needed to help companies, schools and other organizations to get online and understand how to install, configure and operate DNS, e-mail and web server infrastructure.

In 1999 I got involved with the development of netfilter/iptables, the then-experimental new implementation of the Linux packet filter / firewalling code, schedueled for the 2.4.x kernel series. I became one of the netfilter core team members and wes leading it for some time.

netfilter/iptables remains the standard linux packet filter until today (2015). As it has been used by literally billions of devices, from consumer-grade DSL and cable modem routers, to Linux based smart phones (Motorola EXZ, WebOS, Android) to more enterprise-grade systems and products.

As more and more commercial entities started to use netfilter/iptables in their products (which is good!), unfortunately a large number of them were ignorant of the fact that the software is released under the license terms of the GNU GPL. This led to my license enforcement work and the gpl-violations.org project.

Even though I'm not involved anymore with netfilter/iptables, most of my work has been related with communications technology ad/or its security in some way.

Together with friends, I implemented the OpenPCD open hardware RFID reader, complementary to the librfid protocol stack for the ISO 14443 and ISO 15693 protocol stacks. We went on to build OpenPICC, a similar project about emulating a RFID card. Our RFID work has been key to researching the numerous security problems in the Philips/NXP Mifare system, as well as others like Hitag.

I started the OpenEZX project, aiming at providing a Free Software replacement for the overly proprietary Motorola EZX operating system of early smartphones. While the project included a lot of reverse engineering of smart phone hardware and was a lot of fun, it unfortunately was never completed.

I became the lead system architect of the OpenMoko project (and second employee of the OpenMoko company). At OpenMoko, we were developing a modern, Linux based smart phone (hardware and software) at a time before the first iPhone or Android were released. This project received my full dedication between 2006 and 2008.

After having worked on the electronics and software side of a phone, I wanted to go deeper in to mobile communications and started a free sotftware implementation of the GSM protocol stack on the network side (OpenBSC in 2008) and on the mobile phone side (OsmocomBB in 2010). Under the newly-founded Osmocom umbrella project, I countinued to work on other communications sytems, including for example a receive-only implementation for the TETRA professional mobile radio system.

Since 2011, I spend a lot of time working on mostly Digital + RF electrical engineering at my company sysmocom, as well as continued work on the various Osmocom GSM/GPRS protocol implementations.

Short CV



Well, I have to admit a life dedicated to Free Software and such a wide range of technologies doesn't really leave too much spare time for other topics. Before 2005, I still was very fond of photography, particularly the old-fashioned analog/chemical process. I did all the development/prints myself, and it was a lot of fun.

These days, I would guess the only non-IT related hobby is my passion for motor bike ridiing. At this point I own three bikes:

  • A BMW F 650 ST
  • A Yamaha FZ-6 Fazer
  • A Yamaha TW-225 (located in Taiwan)