In the first of my three-part series on securing the post quantum world, I considered what indeterminism means for society – a philosophy that suggests that not all events are wholly determined by antecedent causes. Here, I start to explore some ideas around the possible indeterministic tools we have at hand to protect our deterministic assets.
Securing the world today
To start off, it is important to consider our position on security in society today. No quantum computer will ever easily break the physical keys to my front door, nor will they stop bullets. The security that we speak of is in the digital world, which completely dominates our modern world.
It is important to realize that all the tools used today, be it keys, password registers or PKI cards, are all deterministic security tools. Even a good quantum key distribution network is used to distribute deterministic keys. But the deterministic world cannot protect a world equipped with indeterministic tools. But in the post quantum world, we have indeterministic tools, we just have never used them for security before. So, what could some solutions to these problems be?
The many door principle
The many door principle essentially makes the key surplus to requirement. It answers the question “What if there are no keys to open the door in the first place?” The idea is simple; we use keys to lock doors to keep core assets safe kept behind the door. I could take the key with me and transport it anywhere I want. But what if I can’t observe the door? Using a key on a door that I cannot see by any physical means seems tricky. The not-so-basic quantum twist of this door is of course that it will disappear once I look at it. So only the placer of the door will know where it is. And it requires a distinct way to open it in the first place.
On a quantum network, I can create an entangled state that spans many miles between different quantum computing devices. This means that it is possible to create a container state, spanning many miles and different end-points that together form the same ‘door’-state. Rather than observing the door, I toggle the quantum door-state to make it induce a change without completely observing it. This can result in a spin-off quantum state at my quantum computer.
Let’s say that it is possible to design such a state, that the toggling of the door (perhaps several times) results in my being able to look up information in an otherwise seemingly random set. This door toggling would then essentially tell me where to find the original data, without having to destroy or observe the door-state itself.
The trick is of course the indeterminism of the door. I can use the toggle algorithm at any location, put only at places where the door-state is present, as quantum bits (qubits) from entangled pairs in a quantum network will result in me finding a useful answer. And if I want to observe the door, to see at which quantum computing location the door is present, I destroy the door and my access to it. So only the creator of the door-state knows who can access the data, and puts doors in their front yard accordingly.
This naturally presupposes a few requirements; such as having a fault tolerant quantum internet with confirmed locations, and nobody trying to continuously observe your door-state. The latter is obvious, as any such action would completely defeat the functionality of the quantum computer. The attacker cannot know where to look for the door and would hence have to look at all qubits. Such is an extreme event and highly unlikely to occur. However, it does not provide an answer to the question in which yard I should place the door in the first place…
In the third and final piece of this three-part series, I will consider the ‘many key’ approach to securing core assets in the quantum world.