Quantum Computing’s Threat to Public Key Cryptography
1 Star2 Stars3 Stars4 Stars5 Stars (No Ratings Yet)

Quantum Computing’s Threat to Public Key Cryptography

Could powerful Quantum Computers make today’s encryption methods obsolete?

In the fascinating race for “quantum supremacy,” Google has just steered ahead of the competition with the unveiling of Bristlecone, its most potent quantum computer to date. Bristlecone encompasses 72 qubits, surging ahead of IBM’s latest 50 qubit machine.

Quantum computers are inevitable, and they’re going to change our world in so many different ways. Granted, the term ‘change’ is subjective, and it could mean changes both positive and negative. But when it comes to SSL and encryption, at first blush quantum computing looks like bad (not fake) news!

Before we get to the potential impact that quantum computers could have on encryption technologies, I’d like to take a moment tell you a bit about quantum computers. (If you know what they are and how they work, you can skip this part.)

What Is a Quantum Computer? How Does It Work?

As you’re reading this sentence right now on your computer or smartphone screen, you’d know that there’s a thing called the ‘binary system.’ All of our computers and other such devices have this system at its foundation. All the data/information that our classical computers ingest, process, and store is in binary – 0s and 1s. This 0 or 1 is called a ‘bit.’ A ‘bit’ can either be 0 or 1 at a given time (think of it as a simple on/off switch).

This is precisely where quantum computers differ.

The reason why quantum computers bring along so much buzz and excitement is that they’re fundamentally different. Unlike classical computers, quantum computers operate on particles that can be in superposition. These particles are called ‘quantum bits’ or ‘qubits.’ Due to the principle of superposition, they can be 0 and 1 simultaneously.

I wouldn’t blame you if you’re scratching your head right now. Let me explain this with a simple example.

Imagine you have a coin and a non-transparent box. Keep in mind that this is a normal coin with two sides – heads and tails. Put this coin in the box and lock it out. Now you have to shake the box, let the coin settle down, and predict which side the coin will show. Now here’s a twist. Once you anticipate it in your mind, you don’t open the box. The only way you can know whether it’s heads or tails is by opening the box; you don’t do that. As you haven’t opened the box yet, the coin is both heads and tails according to quantum law. This is regarded as ‘superposition of states.’ Once you open the box, you lose this state of superposition. It’s kind of like ‘You don’t lose if you don’t play.’

As far as quantum computers are concerned, these particles can be assumed to be in two positions simultaneously.

I hope that the frictional force between your scalp and your nail has come down to zero (I’m feeling particularly scientific right now).

How Quantum Computers Could Impact Today’s Most Widely Adopted Encryption Method

One of the main reasons why the RSA (Rivest–Shamir–Adleman) cryptosystem is still not broken is the inability of our classical computers to compute quickly. The RSA algorithm is highly complicated, and it’d be almost impossible for me to explain it here. But let me try to give you a brief idea.

At the heart of RSA lies the concept of prime-factorization. This concept is molded in such a way that it’d take standard desktop computer 6.4 quadrillion (is that even a real number?) years to crack 2048-bit RSA key. That’s because it can try only one combination at a time due to its reliance on bits, and there are billions and billions of possible solutions.

Enters our villain (with heavy-metal music), the quantum computer.

Our normal computers can try only one combination at a time because it’s using bits. Quantum computer, on the other hand, works on qubits. Therefore, a quantum computer operating on a single qubit can try cracking it using two values at a time. Similarly, a QC with two qubits can be in four positions. We can say that a QC with n qubits can try 2n combinations simultaneously. Bristlecone, which has 72 qubits, can try 272 (4, 722, 366, 482, 86,9 645, 213, 696) values.

Now that’s one hell of a number!

You can assume the rest I think!

Do We Need to Worry?

To be fair, there is no straightforward answer to this.

Right now, the quantum computers that we have are in their infancy. To crack the encryption methods that are currently serving us, these computers will have to come a long way. That’s because the road to a fully-fledged, working quantum computer is full of mountain-like challenges.

One thing is for sure though: they will be a reality one day. It’s written in the stars! When exactly? Well, going by the opinion of experts, it will take quantum computers at least ten years to be useful enough. Plenty of time for cryptographers to develop quantum-resistant or quantum-safe encryption methods, right?

Guess what; it’s already started!


Jay Thakkar

After graduating from university with an engineering degree, Jay found his true passion as a writer…specifically, a cybersecurity writer. He’s now a Hashed Out staff writer covering encryption, privacy, cybersecurity best practices, and related topics.