Modern Mo-Soon... Quantum Computer vs Quantum-Resistant Cryptography: Who Will Win? [Reading Science]

Development of Quantum Computers That Can Instantly Solve Any Encryption
Active Research on Quantum-Resistant Cryptography for Cybersecurity

[Asia Economy Reporter Kim Bong-su] When the spear (mo·矛) and the shield (sun·盾) each boasted of being invincible, someone said, "Then try clashing that spear and shield once." There can be no spear that can pierce every shield, nor a shield that can block every spear. The bewildered weapons merchant fled.

A modern paradoxical confrontation is unfolding. The protagonists are quantum computers and quantum-resistant cryptography (QPC). The 'spear' that can break any encryption, quantum computers, are rapidly advancing and approaching commercialization. On the other hand, despite the uncertain future of quantum computers, there are also many who advocate the utility of the 'shield,' quantum-resistant cryptography.

◇ The Emergence of the 'Invincible Spear' Quantum Computer

"Even the most difficult existing encryption can be broken in just a few seconds." What if this becomes a reality? Existing computer security systems such as blockchain would become useless. Personal information leaks would occur, and cryptocurrency transactions like Bitcoin would become practically impossible. The security of all servers could be breached. All computer networks including financial transactions and national security networks could become useless. The problem is that with the emergence and rapid technological development of quantum computers, this issue is increasingly becoming a 'reality.' Quantum computers, a concept introduced in the 1980s, use the concept of qubits (quantum parallelism), which are in a superposition of 0 and 1, unlike traditional digital bits that are either 0 or 1. Although current computers can perform calculations at high speed, they can only perform one calculation at a time, so complex and varied calculations take too long.

In contrast, quantum computers can perform complex calculations quickly, safely, and accurately as the number of qubits increases. This is similar to how the human brain perceives complex surrounding situations simultaneously to make decisions. For example, a 16-qubit quantum computer can perform in one go the number of calculations that a classical computer would have to perform 65,537 times. Especially in 1993, Peter Shor developed a quantum computer algorithm (Shor's algorithm) that solves prime factorization and discrete logarithm problems in real time, sharpening the edge of the 'invincible spear.' This showed the possibility that encryption systems based on public-key cryptography, which rely on difficult mathematical problems like prime factorization and discrete logarithms, could be instantly broken. This meant that encryption systems in all fields such as internet shopping, banking, security, finance, and defense were no longer safe, signaling a 'cryptography crisis' in the cyber world. What if a country or organization secretly develops such a quantum computer? Hacking satellite and nuclear weapon encryption systems or discovering Swiss bank secret codes would become easy.

Quantum computer technology is advancing rapidly. Although it currently requires enormous equipment to maintain ultra-low temperatures and zero gravity, research is underway on methods that can operate at room temperature and atmospheric pressure. McKinsey & Company predicted in February last year that by 2030, about 2,000 to 5,000 quantum computers will be distributed worldwide.

◇ Will Cryptocurrency Security Be Broken Within a Few Years?

IBM, a global leader in quantum computer research, openly flaunts the possibility of developing this 'invincible spear.' At the Korea Science and Technology Annual Conference on the 29th of last month, Won Sung-sik, CEO of IBM Korea, mentioned the possibility of achieving quantum supremacy next year and the neutralization of cryptocurrency security within a few years at the 'Future and Challenges of Quantum Science and Technology' forum. Achieving quantum supremacy means developing a quantum computer superior to existing supercomputers.

CEO Won said, "To achieve quantum supremacy, we need to exceed 1,000 qubits, and we are targeting next year for this milestone," adding, "We plan to commercialize 433 qubits by the end of this year, achieve 1,121 qubits next year, and 4,000 qubits by 2025. Our roadmap anticipates exceeding 100,000 qubits within a few years." Experts expect that once quantum computing surpasses 100,000 qubits, it will have the computational speed to break current cryptocurrency security systems based on blockchain technology, which records transaction histories across multiple computers for verification.

◇ There Is Also an Unbreakable Shield

So, will the advent of quantum computers completely neutralize cybersecurity? A 'shield' is being prepared. These are quantum cryptographic communication and quantum-resistant cryptography technologies that utilize quantum properties. Quantum cryptographic communication is a next-generation secure communication technology that encrypts information by encoding it into photons, the smallest units of light, and transmitting it. Quantum particles have properties such as uncertainty, superposition, and no-cloning. Only the sender and receiver can decrypt the message, and if hacking is attempted, the signal itself is distorted or altered, making original interpretation impossible. Governments and companies worldwide are researching and developing quantum cryptographic key-based encryption systems using these properties. In South Korea, telecommunications companies like SKT and KT have entered the commercialization phase.

Recently, the Korea Institute of Science and Technology (KIST) developed an advanced quantum cryptographic communication technology and transferred it to private companies. This partially resolved challenges for commercializing existing quantum cryptography, such as the current limitation to within 100 km and one-to-one communication. Han Sang-wook, head of KIST's Quantum Information Research Group, explained, "By applying a plug-and-play (PnP) structure using a single light source, we lowered the difficulty required for operating the TF QKD system and developed a system structure that allows simultaneous expansion to many-to-many networks instead of one-to-one." He added, "This is the world's second success and provides foundational technology to lead the field of long-distance quantum cryptographic networks." However, quantum cryptographic communication requires separate devices and stable channels, which limits scalability.

Research on another method, quantum-resistant cryptography, is also active. Quantum-resistant cryptography generates encryption using difficult mathematical problems that are 'expected' to take hundreds of millions of years to solve even with the ultra-high-speed computation of quantum computers. In South Korea, the National Institute for Mathematical Sciences developed a quantum-resistant cryptographic algorithm based on multivariate quadratic equations in April 2020. While Shor's algorithm breaks public-key cryptography based on prime factorization and discrete logarithms, this algorithm solves systems of multivariate quadratic equations, which Shor's algorithm cannot solve. LG U+ announced last year a lattice-based cryptographic method that effectively targets the 'learning with errors' problem, which involves solving linear equations with errors. This technology is embedded in transmission equipment as software for key generation, exchange, storage, and disposal, eliminating the need for separate key management systems and dedicated key exchange lines, thus offering excellent scalability. It was designated as a domestic standard by the Telecommunications Technology Association (TTA) in 2019. These technologies exploit the fact that the more difficult the mathematical problem, the exponentially more qubit resources are required, making it practically impossible for quantum computers to solve them.

◇ The Emergence of the 'Ultra-Ultra Super Spear'

Then, the 'spear' counterattacked again. This time, by South Korean researchers. It was confirmed that quantum-resistant cryptography, no matter how difficult the mathematical problems it uses, can be targeted through quantum computing. The Electronics and Telecommunications Research Institute (ETRI) developed a quantum algorithm in May, together with researchers from KIST, Seoul National University, Hanyang University, and others, that can break quantum-resistant cryptography using a 'divide-and-conquer' strategy. The divide-and-conquer strategy involves breaking down the entire structure into smaller substructures and attacking them individually. Simply put, by dividing an enormous mathematical problem into smaller parts and solving them individually, it was revealed that attacking quantum-resistant cryptography, previously thought impossible even with small-scale quantum computers, is feasible. The research team explained, "We achieved an 'exponential quantum advantage' where the growth pattern of required resources for the problem shifts from exponential to polynomial," adding, "Typically, exponential resource growth classifies a problem as difficult, while polynomial growth classifies it as easy."

However, the war between the spear and shield is far from over. The development pace and trajectory of quantum computers, as well as the outcomes, remain uncertain. Predicting the winner in the battle between quantum computers and quantum-resistant cryptography is practically impossible at present. Even if quantum computers become commercialized, they are expected to complement rather than replace existing computers by handling complex problems such as factorization, advanced calculus, matrix transformations, machine learning, complex optimization problems, and Monte Carlo simulations. For example, optimizing logistics. ExxonMobil, a U.S. oil company, currently optimizes the routes of over 500 LNG ships worldwide, considering geopolitical risks and climate change, with the number of possible logistics scenarios being 2 to the power of 1 million. This is unsolvable by classical computers but can be calculated optimally by quantum computers.

A domestic quantum computer expert said, "Quantum science and technology are becoming a reality. Although there are still technical challenges before reaching general-purpose use, it is expected to take about 20 years," adding, "Considering the impact quantum computers will bring, it is time to prepare for this future technology first."