Feistel ciphers in East Germany in the communist era

ABSTRACT

Feistel ciphers (balanced and unbalanced) represent the most popular symmetric cipher type in modern cryptography. The invention of Feistel ciphers is usually credited to IBM’s Horst Feistel, who co-created the first publicly known encryption algorithm of this type, Lucifer, in the early 1970s. In this publication, the authors will show that Feistel ciphers (or at least a very similar concept) played a surprisingly important role in East Germany in the last two decades of the communism era (i.e., between 1970 and 1990). They will introduce four Feistel ciphers developed by East German cryptologists during these two decades. This includes an unbalanced Feistel cipher that predated RC2, the oldest unbalanced Feistel cipher known in the crypto community (by over a decade), as well as an East German DES variant.

KEYWORDS:

• ALPHA
• BETA
• DELTA
• East Germany
• Feistel cipher
• LAMBDA-1
• SKS V/1
• T-310

Acknowledgement

The authors would like to thank Bernd Lippmann for his support.

Additional information

Notes on contributors

Nicolas Courtois

Nicolas Courtois is a Senior Lecturer at University College London, where he teaches about applied cryptography GA12 and cryptanalysis GA18. His research focuses on the security analysis of cryptographic systems with particular focus on realistic attack scenarios and systems used by millions of users every day. His Google Scholar profile lists more than 100 papers with 7,400 citations in cryptography. His H-index is 37. A university team lead by Nicolas Courtois was given the UK University Cipher Champion in March 2013. He is a founding member of the group Code-Breakers at LinkedIn and a member of the editorial board of Cryptologia. Previously, he was a crypto research engineer at Gemalto, the world’s largest manufacturer of smart cards and secure hardware. He has filed more than ten patents on practical applications of cryptography. He is an expert on security engineering, electronic payment, and crypto currency. His blog is blog.bettercrypto.com.

Jörg Drobick

Jörg Drobick is a German master tradesman in industry and expert for system automation living in Berlin. He grew up in East Germany. After having completed an apprenticeship in a company for instrumentation and control engineering (1980–1983), he worked as a cipher clerk and a cipher machine mechanic for the East German army, NVA (Nationale Volksarmee). Since 1990, Jörg has been engaged in the industry and facility automation. He is a leading expert on East German cryptography, operating a website about this topic (http://scz.bplaced.net/).

Klaus Schmeh

Klaus Schmeh is a German computer scientist, journalist, and speaker in the field of encryption technology. He has published 23 books, over 200 articles, 20 research papers, and almost 800 blog posts mainly about cryptography (many of his publications are in German). He writes a blog (in English) named Klausis Krypto Kolumne about historical cryptology (www.schmeh.org). His latest book, Versteckte Botschaften (2nd edition, Dpunkt, 2017) covers the history of steganography. He is a frequent speaker, who is known for his entertaining presentations, which typically include self-drawn cartoons and Lego brick models. Klaus is a member of the editorial board of Cryptologia.