Already for a few years, quantum computing has been announced as the next revolution that would threaten cryptography as we know it. While a classical computer, based on electronics and Turing’s machine architecture makes computations on binary data (bits worth 0 or 1), a quantum computer relies on quantic qualities of matter and works on qubits which can have an infinity of different values.
Google recently announced they have achieved “quantum supremacy” as their 54-qubit Sycamore processor was able to perform a calculation in 200 seconds that would have taken the world’s most powerful supercomputer 10,000 years. Right after this announcement, IBM, their main competitor in the emerging field of quantum computing disputed the results and said the calculation was feasible on 2.5 days on a classical system. IBM also announced they would soon launch 53-qubit quantum computer.
Most cryptographic systems are based on operations that are considered very difficult or, in other terms, that require an unattainable amount of computing power. For instance, RSA is based on the fact that computing an exponential is fast and easy while factoring an integer is extremely difficult and require lots of computing power or time. As early as 1994, Peter Shor, an American professor of applied mathematics at MIT, developed a polynomial-time quantum algorithm for factoring integers that runs exponentially faster than the best algorithms on classical computers. This remained theoretical for long… until the latest announcements on quantum computing.
When industrialized quantum computers will be delivering the amount of computing power announced theoretically, there is no doubt many of our systems will be under threat. All cryptographic systems that secure our payments, telecommunications, or enterprise security systems will have to be reconsidered in the light of the new realities of computing power. All blockchain-based systems that rely upon asymmetric cryptography may lose their fundamental property of non-reversibility.
While the perspective may sound scary, cryptography experts are already working on developing new generations of algorithms that are expected to resist cryptanalysis by these extremely powerful and fast systems. Quantum computers will not be industrially ready on the short term… but we all have to get ready for the post-quantum world.