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A Dive into Post-Quantum Cryptography: Preparing for the Quantum Era
- Krishna Kandlapelli
- 2 days ago
- 6 min read
Recently, Google unveiled its state of the art quantum computing chip, named Willow. With it came some mind-boggling numbers. Most notably, a computational benchmark that would take the world's fastest supercomputer today - 1025 years (10 septillion years) to compute, would take Willow just 5 minutes to perform. With such great processing power on the horizon, comes great responsibility.
This leap in computational ability isn't just a technological marvel; it's a monumental shift that directly challenges the very foundations that current security systems are built upon. So how does this affect us, and should we be worried? To answer this, this article will explore current and future cryptography, and its impact on society.
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What is cryptography?
Cryptography is the art of masking sensitive information to ensure the secure communication of data. Digitally, this is done by encryption. Think of encryption as the digital lock and key for your data. Encryption is the process in which plaintext, like the text messages you send, is converted into unintelligible cipher text; data is transmitted as cipher text, and once it needs to be decrypted, a key is used depending on the symmetry of the encryption, and its finally converted back into the original plaintext.
There are 2 main types of symmetry when it comes to encryption, symmetric and asymmetric. Symmetric encryption employs the use of a single, shared secret key for both encryption and decryption. On the other hand, asymmetric encryption utilises a pair of keys: a public key to encrypt, which can be freely shared, and a private one to decrypt, which is kept confidential by the recipient. Regardless of the type of encryption, both methods allow for secure transmission of data and protects sensitive information from prying eyes.
Why is Post-Quantum Cryptography (PQC) important?
The actual encryption is done via a series of challenging mathematical formulas, next to impossible for a human to decode in an ample amount of time. Some examples of crypto-system calculations done today are RSA (factoring large composite numbers into their prime factors) and ECC (solving a discrete logarithm problem on elliptic curves). For classical computers, these mathematical problems are severely difficult to solve, an estimated 1000 years to decrypt! However, with the rise of quantum computing, revered crypto-systems such as RSA and ECC can possibly be unraveled within a matter of hours if not minutes.
Fields such as medicine, material science, and of course, technology will be revolutionised with groundbreaking advancements. Yet in spite of this, it also presents profound societal and ethical dilemmas. As discussed, a quantum systems’ ability to break current cryptographic protocols raises significant global security and privacy concerns.
Not to fear, this level of computing isn’t close to stable today, but will be possible in the years and decades to come; and once quantum computers become widely available, they will undoubtedly fall into the hands of criminals with malicious intent. If the current, modern cryptography can’t keep up, sensitive information is at risk of being compromised, worldwide. This begs the question, what can be done to keep our data safe? To understand the answer to that question, classical theories such as binary must be essentially thrown out the window. We have to engage with the very principles that give quantum technology their immense power.
How does it work?
Today's computers run on electrons and transistors. You may have heard of binary, a switch in a computer is either on or off, marked with 1’s and 0’s. This type of computer architecture is efficient for everyday tasks. However, quantum computers are powered by a completely different structure, with electrons, protons, neutrons and photons, collectively forming as qubits. These qubits linger in a state of superposition, and depending on its charge (also known as weight), it can be altered to be any probabilistic combination of on and off. There are 2 types of qubits, physical and logical. Logical qubits are error-corrected and are stable enough to perform reliable quantum computations. They are built using thousands of physical qubits, which are the actual qubits in a system, and are prone to errors and decoherence (which refers to losing the state of superposition).
A computer with just 50 logical qubits, can represent over 1 quadrillion (that’s 15 zeros - 1015) states at any given time. This means instead of processing a solution one step at a time, it can process an enormous amount of solutions in just a single step. It’s important to note that current quantum systems, such as Willow, are nowhere near cracking present security protocols, which would require thousands of perfect, error-corrected logical qubits.
So how do we create cryptography that will be challenging for even the most powerful tech to crack? Currently, there are several approaches, such as code-based, multivariate polynomial, and hash-based cryptography. Nonetheless, the most promising structure is Lattice-based cryptography, as it’s regarded as a front-runner in the space of PQC for its complexity and scalability.
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Imagine a 2-dimensional grid of points arranged in a pattern - this would be a 2D lattice, a pair of vectors within this space can technically reach every single point in the lattice. Now imagine a 3D lattice, and then a 4D, 5D… 100D, 1000D lattice. Hard right? This is the basic structure that complex problems are built upon, that even quantum computers struggle to solve.
An example is the Closest Vector Problem (CVP), where a random point is chosen in a given lattice, and the goal is to find the closest lattice point to the random point. It’s easy to comprehend in a 2D or 3D lattice, but in higher dimensions, this becomes extremely difficult as there are just too many possibilities to check!
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So how does this apply to the process of data transmission and encryption? The sender would have a lattice setup with a ‘good basis’ - meaning the vectors are short and almost perpendicular to each other and clearly define the lattice structure; thus traversing the lattice is precise, quick, and finding the closest point is straightforward. This represents the private key to decrypt the data, which can be seen as the point closest to the randomly chosen point.
On the other side, the receiver would hold the public key, which encrypts the data. The public key would contain the same lattice, but with vectors that are extremely close to being parallel to each other. This means they almost cancel each other out, creating such a high degree of accuracy that when finding the closest point, any miscalculation can lead to completely wrong results, making the problem incredibly computationally intensive.
Furthermore, with the bad basis, the number of possible combinations increases exponentially, which makes brute forcing such a problem impossible. Moreover, with a bad basis, there are no known efficient algorithms to find the closest coordinates. Besides CVP, there are a plethora of other types of problems built upon the lattice structure, and overall, they can make for an extremely resilient private key.
Challenges within society
Quantum computing, while promising a new era across a variety of fields, also presents serious ethical and social challenges. Its ability to break current cryptographic methods poses a threat to global data security protocols, necessitating timely and costly transitions to PQC. This possibly creates barriers for smaller organisations and developing nations that may struggle to keep up with the pace, contributing to a quantum divide where only the most technologically advanced can remain secure.
According to the World Economic Forum, more than 150 countries have no strategy to tackle quantum technology. This disparity can lead to potential misuse and an exploitation of power, allowing for serious issues such as financial manipulation and cyber warfare. This calls for a proper architecture to be developed, that’s accessible to all and secure. Initiative is already being taken with a PQC standardisation process at the National Institute of Standards and Technology (NIST).
Through selecting, testing and developing a set of post-quantum encryption standards, a clear roadmap is being built around PCQ, ensuring a society with a secure future. However, the job is not close to finished; governments, industries, and research institutions must relentlessly collaborate to work upon ethical frameworks, promote transparency through open source initiatives, and invest further in developing quantum technology.
Conclusion
Essentially, quantum computing has the ability to transform industries and research, yet also has the capability to effortlessly compromise data world wide. As we stand on the brink of the quantum era, the choices big tech and governments make today will shape the security and stability of our digital world tomorrow. By proactively investing in PQC and fostering global cooperation, we can harness the transformative potential of quantum computing while safeguarding the privacy and security of individuals, organisations, and nations worldwide.
Reference List
[Reference 1]
[Reference 2]
[Reference 3]
Gitonga, C.K. (2025). The Impact of Quantum Computing on Cryptographic Systems: Urgency of Quantum-Resistant Algorithms and Practical Applications in Cryptography.
European Journal of Information Technologies and Computer Science, [online] 5(1), pp.1–10. doi:https://doi.org/10.24018/compute.2025.5.1.146.
Hidary, J. and Sarkar, A. (2023). The world is heading for a ‘quantum divide’: here’s why it matters. [online] World Economic Forum. Available at: https://www.weforum.org/stories/2023/01/the-world-quantum-divide-why-it-matters-davos2023/.
Magnuson, S. (2019). The Race for Quantum Resistant Cryptography. National Defense, [online] 103(784), pp.25–25. Available at: https://www.jstor.org/stable/27022510.
Neven, H. (2024). Meet Willow, our state-of-the-art quantum chip. [online] Google. Available at: https://blog.google/technology/research/google-willow-quantum-chip/.
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