What Is Post-Quantum Cryptography (PQC)? Practical 2026 Explainer

Currently, the global digital infrastructure of over 70% of companies is reliant on RSA and ECC-based cryptography. This is a huge vulnerability because the quantum threat is right upon us. Google has already set up 2029 as the target milestone of Q-day, which means it won’t be long before adversaries get their hands on it to exploit encrypted systems for the harvested data advantage.

Does a solution to this problem exist? Fortunately, yes.

Post-Quantum Cryptography (PQC) is the answer to this challenge. PQC is a new class of cryptographic algorithms that is designed specifically to secure data against quantum attacks. Today, let's learn what PQC is, what the purpose of post-quantum cryptography is, and how post-quantum cryptography algorithms can be used to protect the future of digital security.

What Is Post-Quantum Cryptography (PQC)?

Simply put, post-quantum cryptography is a cryptographic approach that is designed to protect data and remain secure even against quantum computers. It is a new generation of digital encryption that is built to withstand quantum-based attacks, which would break present-day traditional cryptography.

Traditional cryptography, like RSA and ECC, relies on complex mathematical problems to ensure security. Since these problems are extremely difficult for classical computers to resolve, the encryption becomes secure. With quantum computers, however, these complex problems will be easily solved using Shor’s algorithm which allows decryption and renders current systems vulnerable.

PQC algorithms do not rely on vulnerable mathematical assumptions to function for security. Instead, these algorithms are designed with advanced mathematical structures to create a security foundation which is hard for both classical and quantum computers.

What Is the Purpose of Post Quantum Cryptography?

When it comes to post quantum cryptography, the primary purpose is to protect digital systems and data from quantum threats. The thing is, while large-scale quantum computers are still developing, the threat is quite significant due to the rapid pace of advancement. We can see that quantum computing progress is on the horizon. 

Even Google's quantum processor has made significant progress and we can see how capabilities are improving for the development of quantum systems which may cause current encryption to fail.

The 'Harvest Now, Decrypt Later' Problem:

Apart from future risks, post quantum cryptography is also the answer to the ‘harvest now, decrypt later’ problem. To put it into simpler terms, attackers believe that they can collect encrypted data today and use it later to decrypt it for sensitive information. This could expose the future of secure communications to breaches and cause organizations to lose data.

Post quantum cryptography solves this problem by replacing the use of traditional encryption, which relies on vulnerable algorithms for security. As a result, the encrypted data is protected against future threats and remains secure in both classical and quantum systems.

Five Types of Post-Quantum Cryptography (PQC)

It is important to understand that post quantum is not a single method or algorithm. Instead, it is a conglomerate of five different cryptographic approaches designed to resist quantum attacks on both classical and quantum computers. This classification is similar to grouping based on hardness assumptions of the mathematical problems for which security is defined. Let's explore these approaches one by one:

1. Lattice-Based Cryptography:

First and foremost, lattice-based cryptography is the most studied and most promising category of post quantum cryptography algorithms. It uses mathematical lattices with high-dimensional structures to build cryptographic security. These lattices are complex geometric structures and serve as the foundation for modern encryption schemes, which causes even quantum computers to struggle in solving them.

ARMchain also uses MLDSA, a lattice-based digital signature scheme, for the security layer of its algorithm. This integration allows our systems to operate securely with quantum-resistant cryptography. As a result, users can transact with a high level of security.

2. Hash-Based Cryptography:

Hash-based cryptography is a method that relies on cryptographic hash functions to generate digital signatures instead of algebraic structures. The security of this approach is strong because it relies on the difficulty of reversing hash functions or finding collisions.

This approach is considered highly secure, but hash-based systems can have their own limitations, such as larger signature sizes or restricted use cases, which have limited wider adoption of this category.

3. Code-Based Cryptography:

Code-based cryptography is a scheme which is built on the difficulty of decoding random error-correcting codes. An interesting fact about these is that they have been studied for decades, since the 1970s, and are widely believed to remain resistant even in the quantum era.

However, due to the large key sizes of these systems, code-based cryptography has never really achieved mainstream adoption. But nonetheless, it remains an important candidate for post quantum security.

4. Multivariate Polynomial Cryptography:

MPC cryptography is highly interesting because it uses multivariate polynomial equations to solve hard mathematical problems for secure encryption and signatures. These systems are computationally very hard and prove to be resistant to classical attacks. However, many multivariate schemes have been broken by cryptanalysts over time, which has resulted in this category remaining more experimental compared to lattice-based or hash-based systems.

5. Isogeny-Based Cryptography:

Isogeny-based cryptography is an emerging field and is in its experimental phase. This approach relies on mathematical relationships between isogenies of elliptic curves.

It is considered promising due to its small key sizes, but over the years, some proposed systems have been broken. The research on this area is still ongoing, but it could be an interesting direction in post quantum cryptography.

Comparison of Post-Quantum Cryptography (PQC) Types

Here is a comparison of all the types of post quantum cryptography:

What Type of Post Quantum Cryptography Does ARMchain Use, and Why?

ARMchain uses lattice-based cryptography as its core post quantum cryptography foundation. Specifically, it uses MLDSA for digital signatures and transaction authentication. MLDSA, Module-Lattice-Based Digital Signature Algorithm, is a digital signature scheme that works on lattice-based cryptography. It’s a NIST-standardized algorithm based on the mathematical hardness of module lattice problems, specifically Module Learning with Errors and Module Short Integer Solution. These problems are believed to be intractable for both classical and quantum computers.

The EVM Compatibility Advantage:

Building a new blockchain is not just a technical challenge. It’s an ecosystem challenge. Ethereum has thousands of developers, extensively audited smart contract libraries, battle-tested applications, and accumulated knowledge about secure development practices. Forcing developers to abandon this ecosystem for entirely new programming models is a non-starter.

ARMchain maintains full compatibility with the Ethereum Virtual Machine while adding quantum-enhanced capabilities through specialized opcodes. Existing Solidity contracts run without modification. Development tools like Hardhat, Truffle, and Remix work seamlessly. Developers can migrate applications from Ethereum to ARMchain with minimal friction.

It is highly crucial to understand that post quantum cryptography is not a future upgrade. It is a present-day architectural correction for a future that is already being prepared for.

Final Words

Post-quantum cryptography is no longer a concept of the past. It is very much present and right upon us. In fact, it represents a necessary shift of thinking from classical security assumptions to quantum-resistant design in a world where quantum computing is steadily advancing.

While large-scale adoption challenges and fully scalable quantum machines are not yet here, the underlying breakthroughs in quantum computing are advancing rapidly... and the cryptographic foundations of modern digital systems we rely on today are already being evaluated against future quantum-enabled threats. This whole transition has made post-quantum less of a theoretical upgrade and more of a practical migration in progress.

For blockchain systems, the security stakes are even higher due to long-lived on-chain data and irreversible cryptographic transactions. In this situation, ARMchain’s adoption of lattice-based cryptography reflects a deliberate design choice built for the next security era of quantum resilience.

The question is, are you ready to adapt, or will you wait for the future to decide for you?