The road to quantum cryptography is anything but clearcut

Yesterday, I proposed quantum cryptography as a potential solution to the looming threat of modern cryptography being rendered obsolete by the development of quantum computing. Today, let’s look at some of the challenges and problems associated with bringing quantum cryptography to life.

First, a quick review:

Quantum cryptography is different from modern cryptography in that it encodes private and public keys via the polarization of photons, which are then sent through fiber optic cables and/or high powered lasers around the world.

Sounds simple enough in theory, but in practice it’s anything but.

One of the main problems with quantum cryptography is figuring out how to transfer the photons between two parties, especially when those parties are many thousands of miles away. In order to encode keys through the polarization of individual photons, current quantum cryptography systems rely on low-powered lasers which can be programmed to only emit one photon at a time. With such a low level of energy, those photons become completely unreadable after travelling through a mere hundred miles of fiber optic cable.

That wouldn’t have been such a big problem 300 hundred years ago, but we live in a globalized world where we expect the transmission of secure information to be nearly instant to and from anywhere in the world.

One solution is to just set up booster stations every hundred miles that receive the signal, convert it back to digital data, and then transmit it again through more fiber optics to the final destination or the next intermediary. Of course, this gives rise to another problem which is that anytime the quantum signal is converted to a traditional digital signal, the data becomes susceptible to traditional hacking methods and the quantum encryption becomes useless. Especially if a lot of quantum data is travelling through the same central ground station, someone could just go post up at the receiver and hack away at the goldmine of converted digital signal.

The bottom line here is that if quantum cryptography is going to work, we need to figure out how to transmit the quantum (in the form of individual photons) signal directly to one another without having to convert it back to digital anywhere along the way.

What about satellites? This is certainly one of the more promising solutions, and indeed the Chinese recently launched a $100 million satellite into low earth orbit to assist in transmitting quantum signals. But no solution is perfect, and one major problem with this concept is that anyone would be able to interrupt the transmission of data to and from satellites by emitting an interfering beam of light.

This article is certainly not an exhaustive list of the problems associated with the development of quantum cryptography, but it has presented some of the biggest considerations being tackled right now by scientists around the world. Have any questions or comments about this topic? Leave them below!