Development of the Block Cipher LAMBDA1 in 1990

Abstract

In 1990, it became apparent that the German Democratic Republic (GDR) would leave the socialist community of states. This involved the gradual reduction of cooperation between the cipher services of these countries and the separation of cipher connections. LAMBDA1 is a block cipher developed in East Germany in 1990. It was designed for a cipher device for which a Soviet algorithm was originally intended. The plan was to use a predecessor of the Soviet block cipher algorithm, called GOST. This now had to be replaced. The aim was to provide a cipher algorithm that could not be easily decrypted by either the Warsaw Treaty countries states or the NATO countries. The background to these considerations was the assumption that the GDR would confirm to exist as an independent state for an extended period in a kind of transitional phase. The article describes the circumstances under which the LAMBDA1 algorithm was developed in just one month. It was based on the results of previous projects and was then intensively analyzed. The project was only abandoned when it became clear that the unification of the two German countries would take place at short notice and was imminent. The algorithm below is described only to the extent necessary to understand the development process.