What Is Post-Quantum Cryptography? Future-Proofing Encryption

Discover everything you need to know about post-quantum cryptography and how to prepare your organization for the quantum era.

Nikolina Cveticanin Image
Updated:

November 14,2022

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You may have heard of the term post-quantum cryptography floating around the internet, but what does it mean? Simply put, post-quantum cryptography is a type of cryptography designed to be secure even after quantum computers are developed. 

The emergence of quantum computers is a big concern for many people, as they could potentially break even the most secure encryption methods we use today. That's why it's essential to start preparing for post-quantum cryptography now. In this article, we will discuss what post-quantum cryptography is, how it works, and why it matters.

Post-Quantum Cryptography Definition

It was established way back in the 1980s that if computers took advantage of quantum mechanical properties, their processing speed would increase dramatically. A decade later, mathematician Peter Shor demonstrated how the algorithm used for public key encryption could be easily broken by the (theoretical) quantum computer.

Ever since then, researchers have strived to discover what a post-quantum cryptography system could look like in the future. So, how do you best describe post-quantum cryptography

Post-quantum cryptography (also known as quantum-resistant cryptography) is a type of cryptography designed to be secure against cyberattacks by quantum computers. In other words, this is an effort to develop cryptographic systems for (standard) computers that can stop attacks by quantum computers

The work on post-quantum cryptography is a task that looks toward the future since a large-scale quantum computer hasn’t yet been built, and the current technology is not operating with enough processing power to crack today’s most secure algorithms.

Still, once full-scale quantum computers are developed, we might have to deal with one of the biggest threats to public key cryptography.

Quantum computers with enough processing power will easily be able to break the very foundations of public key algorithms. These are the discrete logarithm, integer factorization, and elliptic-curve discrete logarithm problems. On the other hand, symmetric cryptography is thought to be more resilient.

Pre-Quantum vs. Quantum vs. Post-Quantum Cryptography

Quantum computers process information in qubits, which are quantum bits. This process is done by using the laws of quantum mechanics. A quantum computer is much faster than its “classic” counterpart, thanks to the qubits being combinations of 0s and 1, which results in quicker variable processing. 

Pre-quantum cryptography relies on using a particular type of cipher, known as an algorithm, to transform data that humans can read into a secret code. The difficulty lies in making these ciphers harder to reverse-engineer but easier to understand. 

On the other hand, quantum cryptography uses geometric ciphers and properties of atoms to create an unbreakable secret code from human-readable data. What’s challenging with post-quantum cryptography is that quantum physics is still developing, and it’s very costly to build prototypes for quantum computers. 

Types of Post-Quantum Cryptography

To better understand post-quantum cryptography, we need to explain how different ideas in this field work. There are four post-quantum cryptography types in total, so let’s take a look at what they are and how they work.

Lattice-Based Cryptography 

These cryptographic algorithms are based on the problem with the shortest or nearest vector. This quantum-resistant cryptography deals with the difficulty of solving certain issues on high-dimensional lattices. The most common lattice-based cryptosystem is the NTRUEncrypt algorithm, which is used in a variety of applications, including email and file encryption.

Hash-Based Cryptography 

This type of cryptography derives from a signature scheme that uses only a key pair for signing a message. This signature scheme is known as the one-time signature. If two different notes are signed by an OTS key pair, this might threaten the network, and a hacker might forge signatures and compromise the users’ personal data. 

The most common hash-based cryptosystem is the SHA-3 algorithm, which is used in a variety of applications, including file encryption and digital signatures.

Code-Based Cryptography 

In code-based cryptography, complex mathematical equations are used to create secure cryptographic keys and perform cryptographic operations. This approach is an alternative to public-key cryptosystems and is based on decoding random linear code and solving challenging unknown error-correcting codes.

There are two code-based quantum cryptography techniques: one devised by Robert McEliece and the other by Harald Niederreiter. Unlike other public-key algorithms, code-based cryptography utilizes simple mathematical equations to create and verify cryptographic keys and perform other cryptographic operations.

Multivariate Cryptography 

The foundation of multivariate cryptography schemes lies in the challenge of solving nonlinear equations over finite fields. This type of cryptography relies on using multivariate polynomials, typically of the second degree, and must be solved as an NP-hard problem

In most cases, these polynomials take the form of quadratic equations, though other variations exist that present their own unique challenges. Despite this difficulty, multivariate public key cryptosystems remain popular for encryption thanks to their security and efficiency.

The Importance of Post-Quantum Cryptography

Once developed, quantum computers will easily be able to compromise any cipher developed by a standard computer. This was officially established by a group of researchers from MIT and the University of Innsbruck in 2016

The security issue was recognized as critical during the same year, and submissions were opened for new ciphers that would replace the current public encryption techniques. The National Institute of Standards and Technology, which initiated this post-quantum cryptography competition, developed several defenses during this project. 

One such solution was to double the size of digital keys to increase the number of permutations. This is particularly helpful against brute-force or dictionary attacks

Right now, with a strong focus on post-quantum cryptography, NIST is working toward analyzing and testing numerous techniques so one can be adopted and standardized. There were 69 proposals, and 15 of them were shortlisted

Why Should Organizations Start Acting Now? 

To prepare for the arrival of cryptographically relevant quantum computers and implement PQC measures, organizations will need to invest significant time, money, and effort. The first cryptographically relevant quantum computers are likely to be ready for use during our lifetime, and we can expect that quantum attacks will first target organizations that still use standard computers.

To avoid these attacks, companies will also need to get rid of obsolete archives and records. This process will involve overhauling various aspects of their cryptosystems, such as authenticating users, managing key exchange protocols, and creating digital signatures. As a result, it may take decades for organizations to migrate fully to PQC.

There will be several post-quantum cryptography challenges ahead of us, including understanding the nuances of operating systems and hardware and determining what security measures are already in place.

Nevertheless, preparing for cryptographically relevant quantum computers and adopting adequate PQC measures is vital in staying ahead of future threats from quantum computing technologies.

If your organization hasn't yet updated its systems and processes to comply with the latest cybersecurity standards set by the NIST, you may be at risk of becoming vulnerable to attacks from cybercriminals

This is because many software programs and other digital tools currently use outdated security protocols that sometimes become obsolete as soon as new, more robust cybersecurity standards are released. Therefore, it's essential to align your migration processes with the NIST's standards and implement strong cybersecurity algorithms over time in a systematic way.

What’s the Best Way To Adopt PQC? 

If you're an organization that uses cryptography to keep your communications and data secure, it's essential to begin transitioning to new PQC standards as soon as possible. A multiphased approach can help ensure that your systems and encrypted data remain secure during the transition.

To get started with this transition, you should begin by conducting an inventory of all your systems and applications that rely on cryptography and assessing what algorithms and cryptographic standards are currently in use. This will allow you to identify which of these systems and applications will need to be improved to accommodate the new PQC standards.

Once you've completed this assessment, you can begin improving your crypto-agility. You can do this by developing a plan to quickly incorporate the initial slate of new PQC standards into your systems while ensuring enough flexibility to incorporate additional PQC algorithms in the future. 

To do this effectively, you may also want to test how your current systems perform with the new algorithms.

Bottom Line 

We’ve come a long way since the first idea that there once would be a quantum computer. Technology has evolved to the point that we can now say that the first quantum computer will be operational during our lifetime. That said, cryptographically relevant quantum computers are still in development, and it may be some time before they're ready for widespread adoption.

In the meantime, organizations can take steps to improve their crypto-agility and ensure that their systems are prepared for the transition to quantum-resistant cryptography. Quantum computing technology may pose a potential threat, but the future of cryptography looks bright, and new technologies will improve our existing systems and change how we perceive cybersecurity.

FAQ
What is quantum computing?

Quantum computing is a science field based on quantum theory principles, which explains the behavior of material and energy on subatomic and atomic levels.

How many stable qubits will a quantum computer need to be cryptographically relevant?

A quantum computer will require around 6,000 stable qubits to break a public key and run Shor’s Algorithm.

What is the purpose of post-quantum cryptography?

The primary purpose of post-quantum cryptography is to develop systems that will be secure enough to withstand attacks from regular and quantum computers. These systems need to operate with existing networks and protocols.

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