Explainer: Quantum Resistant Cryptography, Protecting against the Quantum threat

Q-day: When Quantum Computers could break security as we know it

With a different approach to compute compared to classical computers, Quantum Computers can solve certain problems incredibly quickly.

This includes complex factorisation problems, as shown by mathematician Peter Shor's algorithm in the 1990s, which can be used as a tool to crack ECC & RSA security protocols. When Quantum Computers become powerful enought to use such an algorithm to crack existing standards, we'll reach what some commentators call 'Q-day'.

Private companies and nation state are deploying significant capital to accelerate the development of Quantum Computers, while data today is already under threat from 'steal now, decrypt later' attacks.

Quantum Resistant Cryptography: Preparing us for Q-day

To protect our personal, health, company & national security data from the quantum computing threat, new encryption algorithms have been developed and tested by standards bodies around the world.

Led by the National Institute for Standards and Technology (NIST) in the US, the frontrunning algorithms which will protect us are being rigorously tested before being declared in 2024. This group of algorithms are known as 'Quantum Resistant Cryptography'.

The idea has been to develop different encryption methods which are both significantly more complex to solve, for both classical & quantum computing approaches.

Existing encryption standards

Take an assymmetric key algorithm like RSA, where parties have two large, secret, prime numbers, multiplied together to create a unique shared number to encrypt data. These prime numebrs are up to 313 digits long today, and if a classical computer was used to factor these numbers, it could take 316 million years to find each individual's secret key.

It's this factorisation problem that the unique properties of Quantum Computers architecture can be used to best attack RSA using Shor's algorithm.

With a sufficiently powerful Quantum Computer, cracking these standards are well within reach.

Quantum Resistant Cryptography

Take lattice-based cryptography as an example. Lattice based cryptography approaches makes cracking encryption significantly more complex. A lattice, or a series of discrete points across multiple dimensions, is randomly generated by each party. They have their own set of secret and public vectors which help them arrive at a defined point on their lattice (the encryption key) as instructed by their counterparty. This point is obscured by adding randomness (or 'noise').

With the potential for thousands of dimensions, and vectors being secretly held by each of the parties, deccrypting data sent through this message is even too tough for today's conceptualisation of Quantum Computers to solve.

This means, with the right hardware and source of randomness, Quantum Resistant Cryptography can help protect us against Q-day.