When it comes to cryptography, the world is not enough. Nevertheless, the story of cryptography in space has never been told in the crypto history literature. Can you help the HeinzNixdorf MuseumsForum to change this?
The HeinzNixdorf MuseumsForum (HNF) in Paderborn, Germany, is not only the world’s biggest computer museum, but also one of my favourite museums. Their cipher machine collection is currently the best in Germany and one of the most outstanding after the NSA Museum near Washington.
Among the items on display in the HNF are a Wheatstone cryptograph …
…, a Japanese Enigma …
…, an M-94 …
…, and a Kryha Liliput …
…, just to name a few.
Crypto in space
Norbert Ryska, the former director of the HNF, has told me that he is currently doing research in the field of cryptography in aerospace. As far as I know, this topic has never been covered in the crypto history literature in a systematic way. Perhaps, Norbert Ryska and the HNF can change this. And perhaps my readers can provide them information. So, if you have answers to one of the following questions, please let me know.
First of all, it is clear that manned space missions have to communicate with ground control via radio. It certainly makes sense to encrypt this communication. Does a reader have information on how this works?
Encryption becomes even more important when communication with an unmanned spaceship or a satellite is concerned. In this case, control commands sent from ground control to the board computer are crucial. As a fake command may be disastrous in such a scenario, cryptographic authentication is extremely important. Today, implementing an authentication system for space missiles is probably not a big deal any more. The same technology as applied on the internet can be used. Anyway, it would be interesting to have some information about the details. In addition, I ask myself how this was done decades ago, when Public Key Infrastructures and modern cryptographic authentication protocols were still unknown. Does a reader know more about this?
In recent years, the topic of updating a software on a satellite has been discussed among cryptologists (when a satellite is in use for decades, software updates are unavoidable). One potential reason for a software update is that the crypto algorithms used by a satellite have been broken. This easily leads to a vicious circle: the replacement of an insecure crypto system is secured with an insecure crypto system. Such a scenario might become reality when powerful quantum computers are availabe one day. Quantum computers can break virtually all asymmetric crypto algorithms currently in use, including RSA, Diffie-Hellman, and ECC.
To solve this dilemma, crypto experts have developped tools for secure satellite communication based on post-quantum cryptography. These tools usually apply hash-based algorithms, as they are considered secure against quantum computer attacks. In addition, hash-based algorithms are relatively simple and provable secure under certain circumstances. On the other hand, hash-based asymmetric methods are not very convenient – they require long keys that can only be used a limited number of times. For these reasons, hash-based asymmetric crypto algorithms are not meant to be used in every day business of a satellite, but only for securing software updates. Of course, a software update may include the installation of a new crypto algorithm.
Quantum crypto in space?
Last year, reports about satellites implementing Quantum Cryptography on satellites hit the news (Quantum Cryptography is completely different from Post Quantum Cryptography). For me, Quantum Cryptography, which is about using quantum effects for secure communication, has always been kind of a solution without a problem. Quantum Cryptography provides some nice means for key exchange, but I don’t see many applications for this technology – as good as always, conventional methods dothe job as well. We will see what happens in the coming years.
Norbert Ryska is not only interested in cryptography in space but also in error-correcting codes in space. I remember that in the 1990s I read about an error-correcting code that was used by one of the Voyager space probes. Does a reader know more about this?
Further reading: How I explained lettuce-based cryptography at a London conference