Types of Random Number Generators (RNGs): From L1 to L4 RNGs Explained

The Crucial Role of Verified Randomness in Cryptography

Every cryptographic key, certificate, and secure transaction starts with the same requirement: randomness. But randomness that cannot be verified is randomness that cannot be trusted. This is the problem that the RNG classification system — and the principle of Locally Verified Entropy (LOVE™) — exists to solve. Not all random number generators are equal. Understanding the difference is the first step toward a cryptographic foundation that doesn’t ask you to assume anything.

Recognizing the significance of this topic, Quside and Deloitte have collaborated to shed light on the evolving landscape of random number generation. In our joint article, “Quantum Random Number Generators—What’s All the Fuss About?” we delve into how quantum technology advancements enhance cybersecurity. This partnership combines Deloitte’s expertise in cyber readiness with Quside’s pioneering work in quantum random number generation to provide comprehensive insights into RNG types, their classifications, and their impact on security.

On this page, we expand upon our collaboration with Deloitte to offer an in-depth exploration of RNG levels—from the illusion of randomness at Level 1 to the quantified uncertainty of Level 4. We’ll discuss why Level 4 RNGs, like those developed by Quside, represent the pinnacle of cryptographic security and how they are redefining standards in the industry. Whether you’re a cybersecurity professional, a tech enthusiast, or someone interested in the future of digital security, this guide will provide everything you need to know about RNGs from Level 1 to Level 4.

The Foundation of Randomness: Understanding Entropy Sources and DRBGs

Entropy Sources

An entropy source is a mechanism that captures unpredictability from physical phenomena. These could be natural processes like thermal noise, atmospheric noise, or quantum mechanical events. The true randomness in these physical processes provides the raw material needed for secure cryptographic operations. Without a high-quality entropy source, any generated random numbers could be predictable, compromising the entire security system.

 

Deterministic Random Bit Generators (DRBGs)

A DRBG is an algorithm that expands the initial random input (the seed) from the entropy source into a larger sequence of bits that appear random. While DRBGs are essential for producing random-looking sequences efficiently, they do not create randomness on their own—they rely entirely on the unpredictability provided by the entropy source.

 

The Symbiotic Relationship

For an RNG to be secure and effective in cryptographic applications, it must combine a high-quality entropy source with a robust DRBG. The entropy source provides the true randomness, while the DRBG efficiently extends this randomness to meet the demands of modern applications. The security strength of the RNG hinges on the unpredictability of the entropy source; without it, even the best DRBG cannot compensate for poor randomness.

How Do You Measure the Quality of an RNG?

The Challenge of True Randomness

Random-looking sequences can be generated by algorithms, but without true unpredictability, they may be vulnerable to prediction or manipulation. This is particularly dangerous in cryptographic applications, where predictability can lead to security breaches.

 

Common Misconceptions

A widespread mistake is using statistical tests designed for DRBGs to assess the unpredictability of entropy sources. While these tests can indicate whether a sequence appears random, they do not measure the actual entropy or unpredictability. Relying solely on these tests can give a false sense of security.

 

Industry Standards and Guidelines

Recognizing this issue, organizations like the National Institute of Standards and Technology (NIST) have updated their guidelines to clarify the proper use of statistical tests. In April 2022, NIST emphasized that their statistical test suites should not be used to assess cryptographic random number generators for entropy quality.

 

The Importance of Proper Entropy Testing

Proper entropy testing involves analyzing the entropy source directly to ensure it produces unpredictable outputs. This often requires specialized methods and understanding of the physical processes involved. As global standards continue to evolve, collaborating towards unified approaches to entropy assessment is crucial for maintaining robust security.

This is precisely what LOVE™ addresses. Locally Verified Entropy sets a clear bar: entropy quality must be measured at the source, in real time, not inferred from statistical tests after the fact.

Navigating the Levels of Random Number Generation

Not all random number generators are created equal. RNGs can be classified into four levels based on their source of randomness and the quality of entropy they provide. Understanding these levels is essential for selecting the right RNG for your security needs, from basic simulations to critical cryptographic applications.

To continue exploring the RNG types and their impact on cybersecurity, read our collaborative article with Deloitte: Quantum Random Number Generators—What’s All the Fuss About?. This insightful piece delves into the crucial role of randomness in cryptography, how quantum technologies enhance security, and the future of quantum random number generation. Read the full article on Deloitte Insights »

Level 1 RNGs: The Illusion of Randomness

At the most basic level, Level 1 RNGs present an illusion of randomness without providing true unpredictability. These generators often produce outputs that appear random at first glance but are actually deterministic or repeating patterns.

The Danger of Predictable Randomness

Using non-random or poorly implemented RNGs in cryptography can lead to catastrophic security failures. A notable example is the 2010 security breach of the Sony PlayStation 3. Developers used the same random number repeatedly instead of generating a new one for each cryptographic operation. This oversight allowed attackers to reverse-engineer the private keys and compromise the system’s security.


Risks of Level 1 RNGs

  • Predictability: Outputs can be anticipated by attackers, leading to easy exploitation.
  • Repetition: Reusing the same values undermines the very purpose of randomness in cryptography.
  • Vulnerability: Systems relying on Level 1 RNGs are susceptible to attacks that can bypass security measures entirely.

Level 2 RNGs: Opportunistic Randomness

Level 2 RNGs attempt to harness randomness from everyday processes that exhibit seemingly unpredictable behavior. These non-dedicated entropy sources include keyboard typing rhythms, mouse movements, disk drive timings, and variations in network traffic.

Leveraging Everyday Unpredictability

The idea behind Level 2 RNGs is to capitalize on the inherent randomness in human actions and complex system behaviors. Since these sources are readily available, they are often used in situations where dedicated entropy sources are not accessible.


Limitations and Vulnerabilities

  • Predictable Patterns: Human behaviors and system processes often have underlying patterns that can be analyzed and predicted over time.
  • Low Entropy Quality: The amount of true randomness extracted is generally low, making them insufficient for high-security applications.
  • Low Speed: Entropy generation occurs at a very slow rate, which can result in weak entropy vulnerabilities, including issues like entropy starvation and system performance bottlenecks.
  • Exploitation Risk: Attackers can influence or observe these processes to reduce unpredictability, compromising the RNG.

Level 3 RNGs: Engineered Chaos

Level 3 RNGs represent a significant advancement by employing dedicated entropy sources specifically designed for generating randomness. These include components like ring oscillators, avalanche diodes, and basic Quantum Random Number Generators (QRNGs).

Purpose-Built Entropy Sources

  • Ring Oscillators: Utilize feedback loops in electronic circuits to produce high-frequency signals with chaotic behavior.
  • Avalanche Diodes: Leverage the noise created by electron avalanche breakdown, a quantum mechanical effect.
  • Basic QRNGs: Exploit quantum phenomena to generate random numbers.

Advantages

  • Improved Entropy Quality: Dedicated hardware provides better randomness than Levels 1 and 2.
  • Greater Unpredictability: Physical processes used are less susceptible to external prediction or manipulation.

 


Remaining Vulnerabilities

  • Entropy Quality Management: The randomness must be carefully managed and verified to ensure consistency.
  • Statistical Reliance: Many designs depend heavily on statistical tests, which may not fully capture unpredictability.
  • Limited Verification: Physical testing of unpredictability can be impractical or complex, leaving potential gaps in security.

Level 4 RNGs: Quantified Uncertainty

Level 4 RNGs are where entropy stops being assumed and starts being proven. They generate randomness from dedicated physical sources — and critically, they verify the quality of that randomness locally, continuously, and in real time. This is what we call LOVE™: Locally Verified Entropy. Not a claim. A measurement.

Measurable and Verifiable Entropy

  • Model Unpredictability: Provide mathematical and physical models of the entropy source, ensuring randomness is based on fundamental principles.
  • Continuous Assessment: Implement real-time monitoring and testing of the entropy output to detect any anomalies.
  • Provable Security: Offer evidence that the randomness meets the highest standards required for critical cryptographic applications.

The Strongest Cryptographic Foundation

  • Quantum Phenomena Exploitation: using Advanced Quantum RNGs (L4 QRNG), Quside’s entropy sources like Quside Ruby N1 and Ruby S1 utilize processes like phase-diffusion and polarization switching, which are fundamentally unpredictable.
  • Metrology Integration: Implement methods to verify entropy quality continuously and feed your telemetry data pipelines.

Available Today For:

  • Data Centers and Mobile Systems: Enhance security for cloud services and mobile communications.
  • Space Applications: Used in satellites and space communications where security is paramount.
  • Government Systems: Protect sensitive data within governmental agencies.

Quside L4 QRNG

Quside: Pioneering Level 4 Quantum RNG Technology

Quside builds Level 4 Quantum Random Number Generators designed around a single principle: entropy must be verified at the source, not assumed. Our devices generate randomness from quantum optical processes — and measure its quality in real time, locally, on every deployment.

Fast and Measurable Randomness

Advanced QRNG (L4 QRNG)

Leveraging quantum phenomena, our devices generate randomness that is both measurable and verifiable.

SP800-90B-compliant

Our entropy sources meet the rigorous certification standards set by NIST, ensuring the highest levels of entropy and reliability.

Real-Time Entropy Verification

Advanced Observability: continuous monitoring ensures the integrity of the random numbers produced.

Robust Physical Models

Built upon well-understood quantum mechanical principles, providing provable security foundations.

Key Features of Quside's QRNGs

Scalability

Available in various form factors, from compact chips to high-throughput appliances.

Ease of Integration

Designed for compatibility with existing systems without significant overhauls.

Cost-Effectiveness

With different performance tiers, we aim to reduce costs and facilitate wider adoption, making our products accessible to new markets with higher volume demands.

Crypto-agility

Enhancing your security posture with both current and emerging threats, including those posed by quantum computing.

Listen the Podcast!!

Guess what happens when you feed an article on RNGs to AI? You get an awesome podcast!

We decided to see what AI could do with Deloitte’s deep dive on RNGs, expecting maybe a summary or two. Instead, it produced a surprisingly enlightening podcast packed with great examples! Who knew AI could be such a natural storyteller?
If you’re interested in cybersecurity, quantum randomness, or just want to hear an AI’s take on complex topics, give it a listen. Sometimes the best insights come from the most unexpected places!

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Testimonials

What Our Customers & Partners Say

Combining PQShield’s PQSDK with Quside’s QRNGs delivers even wider options for developers to integrate quantum-safe cryptography into their applications easily. This integration is also nicely timed with the full release of the NIST PQC standards in August 2024


Ben Packman
Chief Strategy Officer at PQShield

As businesses seek ever more sophisticated solutions for modern problems, Equinix is proud to support the growth, scale and democratisation of the quantum industry. Working with businesses such as Quside provides our customers in Spain and around the world with unique access to some of the most innovative security solutions on the planet for the on-going transition to quantum-safe cybersecurity and efficient randomized accelerated computation.


Eulalia Flo
Managing Director for Equinix, Spain

At Telefónica, we persistently evolve our understanding of the future to transform it into reality. These quantum-safe developments will enable Telefónica and its customers to benefit from enhanced security with easier deployment. End users will also gain from the assurance of uninterrupted services and protection against advanced cyber threats during the whole device’s lifetime.

 


Antonio Guzmán
Discovery Director at Telefónica Innovación Digital
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Join the Future of Secure Communications with Quside

Every cryptographic key your systems generate depends on entropy. Most organisations assume that entropy is fine. Level 4 changes that — because with LOVE, entropy is no longer invisible infrastructure. It is measured, observable, and verified at the source. That is what Quside builds. And it is available today. Join the organisations that verify their entropy.

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Why Choose Quside's Level 4 RNGs?

Unparalleled Security

Leverage true quantum randomness for the highest level of unpredictability.


SP800-90B-compliant

Meet and exceed international security standards and guidelines.


Scalability

Solutions designed to meet the demands of various applications and industries.


Cost-Effectiveness

Optimized for deployment at scale, reducing overall security costs.


Ease of Integration

Compatible with existing hardware and software infrastructures.


Love-Compliant

Quside QRNGs provide locally, continuously, and observably verified entropy at the source.


Resources

Expand Your Knowledge

Stay informed about the latest developments in quantum technology and cryptographic security.

High-security point-to-point network

A customer recently deployed a CV-QKD link to protect 2 high-security end points, using Quside’s FMC 400 to produce the basis choices in real-time.

Acceleration of randomized workloads

Using Quside’s Randomness Acceleration Platform, our client was able to demonstrate up to 10x speed on the randomness consumption bottleneck for their Monte Carlo-based financial models.

Secure GEO-satellite QKD communication

Quside with its FMC400 architecture is part of a consortium developing the first European GEO-satellite QKD system for the distribution of unbreakable encryption keys over distances larger than 100 km with high availability.

Cloud-based and quantum-safe.

A customer launched integrated Quside’s Quantum Entropy products to build and appliance that is supporting a novel cloud-based secutiry infrastructure.

Co-founder & CEO

Carlos Abellan

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.

FAQs

Answer your question about new QRNGs categorization

What types of Random Number Generators (RNGs) exist?

There are two main types of RNGs: Pseudorandom Number Generators (PRNGs) and True Random Number Generators (TRNGs). PRNGs rely on deterministic algorithms to generate numbers that appear random but can be predictable if the algorithm is known. TRNGs, on the other hand, generate randomness based on unpredictable physical processes, such as quantum phenomena, making them ideal for high-security applications.


What is a Quantum Random Number Generator (QRNG)?

QRNGs are a subset of TRNG devices that use quantum mechanical properties to generate random numbers. Quantum phenomena are naturally unpredictable, guaranteeing that the numbers produced are genuinely random, free from any biases or predictable patterns.


What is the classification of RNG levels?

RNGs are classified into four levels based on the quality and unpredictability of the randomness they provide:

  • Level 1: Pseudorandomness, where numbers appear random but can be predictable.
  • Level 2: Opportunistic randomness, relying on non-dedicated entropy sources like mouse movements or network jitter.
  • Level 3: Engineered randomness, using dedicated hardware like ring oscillators, avalanche diodes, and even some quantum random number generators but without real-time verification.
  • Level 4: Quantified Uncertainty, where randomness is generated through measurable physical processes, including real-time verification of entropy quality, providing the highest level of security.

What are the differences between Level 3 and Level 4 RNGs?

Level 3 RNGs use dedicated hardware to generate randomness but cannot continuously verify entropy quality in real-time. This means that, while randomness is generated, it might not consistently maintain the highest security standards. Level 4 RNGs, however, use quantum phenomena to create numbers and offer real-time verification to ensure the randomness always remains genuinely unpredictable and secure.


What is a Level 4 in random number generators (L4 RNG)?

Level 4 RNGs represent the pinnacle of random number generation technology. They employ measurable entropy sources that are not only purposefully designed but also provably quantifiable and continuously verifiable during operation.


What makes Level 4 RNGs different from other levels?

Unlike lower levels, which rely on deterministic or physical processes that can sometimes be predictable, Level 4 RNGs generate random numbers based on quantum processes that are inherently unpredictable. Moreover, it continuously verifies the quality of the randomness, ensuring consistent security.


Why is real-time verification of randomness a key feature of Level 4 RNGs?

Real-time verification of entropy in Level 4 RNGs ensures that the generated random numbers remain completely random over time. If there is any drop in entropy quality, the system can immediately detect and correct it, which is critical for maintaining security in high-stakes applications.


How does Level 4 prevent “entropy starvation”?

Level 4 RNGs prevent entropy starvation by continuously generating quantifiable high-quality entropy. This ensures sufficient randomness is always available to maintain cryptographic security, a common issue in lower-level systems.


In which applications are Level 4 RNGs most useful?

Level 4 RNGs are ideal for high-security data centers, financial systems, government communications, and space missions. These applications require not just genuine randomness but also the ability to verify and guarantee that randomness in real-time.


What risks can be avoided using Level 4 instead of lower levels?

Lower-level generators may produce random but predictable numbers, exposing systems to cyberattacks. Level 4 significantly reduces these risks with its truly unpredictable randomness and continuous verification.


How do Level 4 RNGs differ from lower-level RNGs?

Level 4 RNGs provide true randomness with real-time verification, ensuring the numbers are genuinely unpredictable and continuously monitored for quality. Lower-level RNGs (Levels 1 to 3) may generate random numbers. Still, they either rely on deterministic algorithms (Level 1), non-dedicated sources (Level 2), or dedicated hardware without verification (Level 3), including some QRNGs, making them less secure and more vulnerable to attacks.


How is randomness generated in Level 4 RNG systems?

In Level 4 RNG systems, randomness is generated by leveraging physical and/or quantum phenomena, such as phase diffusion or polarization switching. These phenomena are entirely unpredictable, ensuring true randomness.


Are Level 4 RNGs already in use?

Yes, Level 4 RNGs are already used in sectors such as space, data centers, and government applications. Their ability to provide genuine, verifiable randomness makes them a leading solution for securing critical infrastructures. Quside’s Level 4 RNGs are available in different form factors (chip, embedded, pcie…).


What happens if the quality of randomness in a Level 4 RNG decreases?

If the quality of randomness decreases, Level 4 RNG systems detect the anomaly immediately through their real-time verification capabilities. This allows the system to adjust or correct the random number generation process to maintain security and produce new high-quality entropy