Quantum Hacking: How Safe Are Your Secrets From a Quantum Computer?
Quantum computers are getting better all the time. So you had better watch out. Quantum computers are capable of breaking highly complex codes very fast - including the ones that guard our online data today. So how safe are our secrets from one of these computers?
Nowadays, we are transmitting vast quantities of private data: from emails to documents in the cloud or online banking transactions. Privacy is ensured by means of "encryption". These are digital keys to secure the data and it works a bit like a safe: you can only access the information in the safe if you have the right key. The lock is usually a number hundreds or sometimes even thousands of digits long, and the corresponding key consists of two numbers that have to be multiplied by each other to give the number that will unlock it.
Quantum hacker
A hacker with a normal computer could never crack a digital lock like this - it takes an immense amount of time to work out the key that goes with a particular lock. If they had a powerful quantum computer, however, they could do it. Today's computers work with bits (zeros and ones), but a quantum computer uses "qubits" and these - thanks to the bizarre laws of the quantum world - can be a 0 and a 1 at the same time. This allows the computer to perform multiple calculations simultaneously, making it a lot faster. In other words, it can calculate the key numbers that will break a numerical code in just a few hours. Bang goes your security!
Quantum key
So far there are no quantum computers powerful enough to actually do this, but some experts estimate that they will be available within a decade. Besides, the quantum computer will then be able to hack into security retroactively, so hackers can collect encrypted information now and decode it a few years from now.
To keep state and banking secrets secret in future, people are therefore already working on post-quantum cryptography. In 2016 the U.S. National Institute of Standards and Technology (NIST) launched a global competition for cryptographers to find quantum-proof alternatives. Only a few of the dozens of entries are still intact today.
Some people are adopting the "if you can't beat them, join them" approach: using quantum technology itself as protection. "Quantum key distribution", for example, sends light particles and measures their properties on arrival. If you attempt to copy any of this information, the original information is changed. So what is the downside? Communication using light particles requires quantum networks (which are not yet sufficiently widely available), it is prone to errors and it does not (yet) work very well over long distances.
The future
Experts believe that combining these two security methods (post-quantum cryptography and quantum key distribution) will result in a solution that could protect sensitive information. However, it is still difficult to predict whether these methods will still be secure enough in the distant future.