I will discuss how to break GEA-1. The attack is based on a very particular relation between two out of the three LFSRs internally used by GEA-1. As this is very unlikely to happen by chance, there is a strong indication that the security of GEA-1 was deliberately weakened to 40 bits in order to fulfil European export restrictions. I will also briefly how to construct corresponding sets of LFSRs.
Gregor Leander received his diploma degree in mathematics in 2001 from the University of Bremen, Germany. In 2004 he received his Ph.D.\@ degree, focusing on the study of Boolean functions, from the Ruhr University Bochum, Germany under the supervision of Hans Dobbertin. From 2006 to 2007 he spent one year as a post-doctoral researcher at the University of Toulon in France. From 2008 to 2012 he was an associate professor at the Technical University of Denmark in Lyngby, before he returned to the Ruhr University Bochum in 2013. Since 2015 he is a professor at the Ruhr University Bochum. His research interests include the study of Boolean functions and the design and analysis of symmetric cryptography