Programming with Python: Understanding and implementing double-cube encryption

Programming with Python: Understanding and implementing double-cube encryption The principle Let Python do the math Interview: Klaus Schmeh on the security of the double-cube Read the article in c’t 22/2023

Two inconspicuous people meet on a bridge and exchange a scrap of paper with a handshake. On it are words that are all five letters long and, on closer inspection, do not resemble any known language. Should one of the two spies be caught later, there is nothing on his body apart from the note that could provide a clue to the message.

During the Cold War, it was not uncommon for agents to encode their messages using a cipher called a double cube, which was carried out with pen and paper without the use of special utensils. All you needed were two keywords that you defined in advance. This simplicity was an advantage over other methods that required a machine like the Enigma or a code table. Should such funds fall into the hands of third parties, the security of the process or, worse, the lives of the agents would be at risk.

Double dice is also an easy-to-remember process, without any numbers or formulas, that only takes a few minutes. Sure, you can leave a task like this to a computer today, which will immediately spit out the encrypted ciphertext at the touch of a button. We also programmed such a Python program and present it in this article. However, it still makes sense to first play through an example cipher with pen and paper so that you can understand the program more easily later on.

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