Dr. Ralph Wernsdorf

The mathematician at the Rohde & Schwarz SIT GmbH works on block ciphers

Ralph Wernsdorf studied mathematics of the Humboldt-University zu Berlin and got his degrees in 1980 (Diploma) and 1983 (Ph.D). He is an employee of Rohde & Schwarz SIT GmbH, which is located in Berlin-Adlershof since 2002. The company develops and offers encryption solutions for secure communications in critical infrastructures. Examples can be seen in the figure: Equipment which protects phone calls against eavesdropping and sensitive data during their transmission via public networks.

Dr. Wernsdorf worked in several projects, studies and product developments in the area of IT-security. As “head of cryptology fundamentals“ he together with his team solved demanding mathematical and cryptographic tasks. Together with colleagues he wrote a series of contributions to scientific conferences and other publications (for example for the Journal „Discrete Applied Mathematics“), especially about algebraic properties of block ciphers.

His research focus

Most of the known block ciphers are characterized by the successive application of so called round functions. Each round function performs a reversible transformation (permutation) of the plaintext with the usage of a key-dependent parameter. Properties of the permutation group which is generated by these round functions can be important for the security of the encryption algorithm. If this permutation group is too small then this can cause cryptographic weaknesses. For several known block ciphers (e.g. the AES) it is proved that the alternating group (a large permutation group) is generated.

Contact: Dr. Ralph Wernsdorf, e-mail, tel.: +49 30 65884-222, www.sit.rohde-schwarz.com