Future quantum computers have the potential to crack today's internet encryption

Mathematician Peter Shor — creator of the revolutionary method for making quantum computers possible — now warns that quantum computing threatens to crack the encryption coding used by conventional computers.

In 1995, when Shor first published his algorithm showing how a quantum computer could factor integers into prime factors in fractions of a second, quantum computers were purely theoretical.

Today, because of its promise to speedily perform very large computations, quantum computing is a growing, venture capital-funded research area for start-up tech companies.

NASA, for example, wants to use quantum computing in its space missions and in developing new aerospace materials. Manufacturing and financial businesses, among others, are also considering the data applications of quantum computers.

NASA is collaborating with Google, which last year demonstrated a first-generation quantum computer called Sycamore. Sycamore successfully competed against a traditional supercomputer, completing a calculation that Google estimated would have taken a supercomputer 10,000 years to complete.

An Internet security warning

Nature Magazine recently published an interview with Shor about his warning on internet security.

Shor, a professor at the Massachusetts Institute of Technology, noted that today's quantum computers do not yet pose a threat to conventional computer encryption. But, he said, the possibility is on the horizon that future quantum computers will crack the current prime number-based encryption code known as RSA.

Asked by interviewer Davide Castelvecchi what might securely replace RSA in the quantum computer age, Shor said: "I think we have post-quantum cryptosystems that you could replace RSA with. RSA is not the big problem right now. The big problem is that there are other ways to break internet security, such as badly programmed software, viruses, sending information to some not entirely honest player. I think the only obstruction to replacing RSA with a secure post-quantum cryptosystem will be will-power and programming time. I think it’s something we know how to do; it’s just not clear that we’ll do it in time."

Shor said that, with an enormous effort, we could switch to a post-quantum encryption system. The question is timing. 

"If we wait around too long, it will be too late," Shor said.

The quantum advantage

The quantum computing advantage is based on the use of qubits (quantum bits), instead of binary bits (1s and 0s) that are electrically or optically transmitted to convey information.

Qubits are usually subatomic particles (electrons or photons) that can be manipulated because of their quantum properties to be in several different, yet predictable, combinations simultaneously (superposition and entanglement). The qubit flexibility can exponentially increase the speed of computations.

Taking advantage of quantum properties is complicated though, because qubits are difficult to generate and fragile to work with, making them error prone.

Shor's 1995 algorithm paper proposed a way to measure the error without destroying the computation.

The problem in a limerick

Shor is also a published poet. He and his wife wrote the following limerick about the problem for a poetry contest in Science News:

If computers that you build are quantum, 

Then spies of all factions will want 'em. 

Our codes will all fail, 

And they'll read our email, 

Till we've crypto that's quantum, and daunt 'em.