# What is a Quantum Random Number Generator (QRNG)?

## Random number generators and cryptography

Every time you send an email, connect to your bank account or check your medical examination, you rely on random numbers to protect the security of your online activity. Cryptography is the set of tools we use to keep us safe online, and random numbers are the foundation in which cryptography is built upon. In other words, if we could not generate unpredictable random digits, secure online communications would not be possible.

While there are many ways to generate “random numbers”, not all of them are good enough for cryptographic use. For instance, computers are unable to produce random digits on their own, unless we help them with external hardware means. The reason is simple: a computer is a machine designed to reliably execute one instruction after another, in a completely predictable and repeatable way.

That said, computers have functions and instructions to generate so-called pseudo-random numbers (PRNGs), which produce sequences of digits with certain “random” statistical properties. But the random numbers produced from a PRNG are completely predictable and therefore cannot be used “as is” for cryptographic applications.

The way to bring randomness (or unpredictability, to be more precise) to computers for cryptographic use is via so-called true random number generators (TRNGs).

## How do true random number generators (TRNGs) work?

TRNGs are based on measuring a specific (random) physical process to produce random digits. Thus, the randomness of such numbers comes from the underlying physical process, which may indeed be completely unpredictable. TRNGs are the baseline for security applications.

TRNGs are hardware components and sophisticated engineering is required to build them properly. Unfortunately, current communication systems rely on weak TRNG designs, compromising security and/or performance of the communications. There are mainly two reasons for this reliance on weak TRNG designs. First, some systems do not even have a dedicated TRNG hardware component, due to cost or design choice, thus relying on generic components in the system to produce random samples (e.g., clock interrupts from the operating system). Second, many TRNGs are designed based on physical principles that are complex and therefore produce “random-looking” dynamics (e.g., chaos), but which are, by principle, predictable and deterministic, which a sufficiently motivated attacker or a badly operated system may reveal to compromise security.

Building reliable, fast and unpredictable TRNGs is essential for the present and future of cryptography. And Quantum technologies are now being used to produce quantum-enhanced TRNGs, that is How do quantum number generators work.

## What is a quantum random number generator?

Quantum random number generators (QRNGs) are a special case of TRNG, that generate randomness by measuring quantum processes, which are, by nature non-deterministic. The advantages are multiple, including a fundamental advantage in using quantum indeterminacy, typically faster performances by leveraging photonics and most importantly, the ability to understand and verify the origin of unpredictability, which is a core assurance for the entire cybersecurity chain.

Until now, engineering high-quality, scalable and fast quantum random number generators has been a challenge to date, and this is the area Quside has been pushing to advance over the last decade. Our proprietary technology allows for fast, high-quality, and scalable production, leading to a solution that is ready for today’s unpredictability concerns and tomorrow’s performance requirements.

## Fast and measurable random number solutions by Quside

Quside has been researching, engineering and producing high-quality QRNGs for over a decade. The proprietary technology that Quside has put together provides 3 major advantages:

1. Fast: Quside products can generate hundreds of Mb/s and even Gb/s already today. We leverage photonics to produce very fast random streams.
2. Measurable: using our peer-reviewed Randomness Metrology methods, our customers can access transparently quality metrics that directly relate to the quantum physical principle responsible for unpredictability.
3. Unpredictable: we use a largely peer-reviewed quantum process to generate randomness, thus harnessing nature to enhance entropy production.

Additionally, Quside has also put a major effort on scaling the technology, which can be today produced at scale using photonic integrated chips (PICs).

## How are quantum random numbers generated?

About Quside’s phase-diffusion technology, Quside QRNGs are based on the phase-diffusion process in semiconductor lasers. The core element of the technology is converting microscopic quantum observables, which are delicate and hard to measure, into macroscopic dynamics that are robust and easy to capture. To do this, we modulate a semiconductor laser from below to above its threshold level or produce a stream of phase randomized optical pulses. This is called gain-switching.

Then, we use an interferometer to convert the phase fluctuations into the amplitude domain, generating a stream of amplitude-randomized optical pulses at the output (see refs [2, 3] for two examples of interferometers that we use). Finally, a fast photodiode converts the photonic signal into the electronic domain, where standard electronics are used for turning the analog signal into the digital realm.

At the heart, the unpredictability of the phase-diffusion technology traces back to the process of spontaneous emission, which occurs as a result of the interaction between the quantum vacuum field and the laser’s gain medium. Quside’s technology exploits this quantum-mechanical process to produce quantum-based random numbers at multiple Gigabits per second.

## More about the Randomness metrology

Testing randomness is a complex matter and the way it has been traditionally done is completely flawed. The question “how do you know it is random?” is a hard one to answer, and this is an area where we have been working since 2012, introducing our randomness metrology methodology in 2014 and collaborating with world-leading researchers from NIST, IQOQI and TU Delft to apply it in landmark experiments.

Our methodology defines strict quality bounds on all our devices to capture the quality of the unpredictability we produce, and the best part is that we can confidently do it in a transparent manner. This boosts trust and confidence with our customers, who do not have to rely on black boxes anymore for producing their cryptographic material.

In many traditional TRNGs, not based on quantum processes, it is extremely hard or even impossible to place rigorous quality bounds. As randomness is not emerging from a fundamentally random process.

## Quantum Random Number Generator solutions

Start using fast and measurable quantum randomness with Quside. Securing communications is undeniably one of the most important endeavors of our society today. New cryptographic standards are now emerging, to enhance even further our protection and governments are releasing their mandates to transition the security of their networks and data, as the Quantum Computing Preparedness Cybersecurity Act by the US government on July 14th, 2022.

Migrating to the new post-quantum standards with a hybrid security approach in mind is essential and the time to act is now and building a strong randomness generation foundation on which the new standards can rely upon is equally important.

Remember that no security can be achieved unless we can produce unpredictable random numbers, and the question is: are we producing them? How do we now? Using the highest quality randomness generation technologies and monitoring them properly is where Quside can get you to the next level.

Carlos Abellan

Co-funder & CEO

PhD in quantum technologies at ICFO, where he developed the quantum randomness technologies that were transferred to Quside. 10 years of experience in quantum and photonics technologies, co-inventor of multiple patent families and co-author of 15+ papers in top scientific journals. Received the award MIT Innovators Under 35 Europe.

Want to hear more about the quantum side?

STAY CONNECTED AND GET THE LATEST NEWS
RELATED POSTS
Can quantum random number generators improve computational results?

A research collaboration between Quside, ICFO, and others, has shown how using quantum random number generators provide the required quality and efficiency for safely running even the most complex stochastic simulations.

Quantum random numbers for physics-inspired optimization problems

Making decisions is commonly a challenge due to the uncertainty and overwhelming information needed to deal with a problem: from every engineering design, data analysis or most business decisions to...

Cyber Attacks and Ransomware: What You Need To Know

Cybercriminals don’t take vacations and the list of cyber attacks and ransomware keeps increasing throughout the year.