There are many projects I worked on:
tpm4java is a java API for communicating with a trusted platform module on a PC. It was designed and implemented by Martin Hermanowski and me.
BouncyCastle is a cryptographic library for Java. In my bachelor thesis, I designed and implemented a TLS client stack for BouncyCastle, that is now part of the project.
aircrack-ng is a toolsuite for analyzing and auditing WLANs. In my diploma thesis, I designed new attacks on WEP, an encryption protocol for such networks. Meanwhile, the attack is integrated in aircrack-ng.
dedected.org is a project to investigate DECT and DECT security more closely. Many people participated here. I was working mostly on the reverse engineering and analysis of the cryptographic algorithms used in DECT.