Shim Kyunga, head of the Public Infrastructure Research Division at the National Institute for Mathematical Sciences (NIMS) and an authority in this field, explains the essence of cryptography research as follows. In 2020, she led her research team to develop a "high-speed cryptographic technology invulnerable even to quantum computers," marking a turning point in earning global recognition for Korean cryptographic technology.

The United Nations (UN) has designated 2025 as the "International Year of Quantum Science." The scientific community views this as the inaugural year of transition from an era dominated by digital technology to one led by quantum technology. And in the midst of this change, the busiest people are cryptography researchers.

This is because the advent of quantum computers is imminent. The encryption technologies we use today rely on mathematical problems that are difficult for current computers to solve. However, once quantum computers advance sufficiently, existing encryption systems could be rapidly rendered obsolete.

Kim Kwangjo, Professor Emeritus at KAIST, has been warning about this issue for a long time. He pointed out, "In 1994, when mathematician Peter Shor announced the 'Shor's algorithm' that could undermine the core principles of existing cryptography, quantum computers were still considered a technology of the distant future. But in just 30 years, the cryptographic technologies we use today have become exposed to a fatal threat."

Professor Kim is the first Korean to be selected as a Fellow of the International Association for Cryptologic Research (IACR), making him one of the top authorities in this field. In 2021, he developed the post-quantum electronic signature "SOLMAE" with superior performance compared to existing methods at the U.S. National Institute of Standards and Technology (NIST), and this year, he is working to have it designated as a Korean standard.

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Director Shim also expressed the same concern. "If quantum computers emerge, the cryptographic technologies we use on the internet today are highly likely to become insecure," she emphasized, adding, "To ensure secure communications and data protection in the future, it is essential to transition our cryptographic systems to 'Post-Quantum Cryptography (PQC).' "

PQC refers to cryptographic technologies that cannot be easily broken even by quantum computers. Current encryption relies on the difficulty of solving certain mathematical problems, but if these problems are solved, the encryption is also broken. PQC is a new cryptographic system that applies methods difficult for even quantum computers to solve, thus avoiding this risk. Both experts agree: "The transition to PQC must be accelerated."

　Shim Kyunga, Head of Suryeon Research Center

PQC, a new encryption system that quantum computers cannot solve,
is essential
Safe communication and data protection are necessary
Lattice-based encryption can also be cracked in 10 years

　Kim Kwangjo, Professor Emeritus at KAIST

When the 'Shor algorithm' was announced,
quantum computers were considered a distant future
Now exposed as a critical threat in 30 years
May appear as soon as 5 years or at latest within 20 years

Photo by Pixabay

PQC is a cryptographic technology that protects information in a way that cannot be easily broken, not only by conventional computers but also by powerful quantum computers of the future. This technology maintains security by relying on the principle that certain mathematical problems are hard to solve. However, if these mathematical problems are solved, the encryption is no longer secure.

One of the most widely used cryptographic technologies is RSA. Developed in 1978 by Ronald Rivest, Adi Shamir, and Leonard Adleman, RSA is based on the mathematical principle that multiplying two very large prime numbers is easy, but factoring the resulting number back into its original primes is extremely difficult.

With conventional computers, this calculation takes an enormous amount of time, which is why RSA encryption has been considered secure. However, with the advent of "Shor's algorithm," a new computational method, it has become known that quantum computers can solve this factoring problem very quickly. As a result, there is a possibility that existing encryption methods, including RSA, may no longer be secure.

PQC was developed to address this issue. PQC includes various cryptographic methods, most notably lattice-based cryptography, multivariate polynomial cryptography, and hash-based cryptography. Among these, lattice-based cryptography is currently regarded as the most secure, as it is considered difficult to break even with known quantum algorithms.

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A lattice, simply put, is a set of regularly arranged points, like intersections on a Go board. Starting from any point, moving the same distance in a specific direction will always land you on another point. While lattices made up of points and lines can be easily visualized in two-dimensional space, in cryptography, they are used in much higher dimensions (n dimensions).

As the number of dimensions increases, the number of possible points grows exponentially, and the computational workload required for a computer to process them increases explosively in proportion to 2 to the power of n. This is why high-dimensional lattice problems form the basis of cryptographic technologies that are difficult to solve, even with quantum computers.

The important point here is that lattice-based cryptography is not absolutely unbreakable, but it is extremely difficult to break with existing algorithms. Scientists currently regard lattice-based cryptography as the strongest among available cryptographic technologies, and believe it is likely to remain secure for at least 10 more years, even as quantum computers continue to develop. This means that lattice-based cryptography can maintain its security for a certain period even after quantum computers become practical.

Director Shim explained, "Since a lattice is a set of points expressed as integer linear combinations in n-dimensional space, the higher the dimension, the more difficult it is to attack. However, if the dimension is too high, the computational workload increases and speed may decrease. While it is currently difficult to break, more efficient attack methods could be developed in the future, so increasing the key length, such as the dimension, is necessary to counter attacks."

In fact, in May 2022, a research team at the Electronics and Telecommunications Research Institute in Korea made headlines by developing a quantum algorithm that could target PQC using a "divide and conquer strategy" for the first time in the world. Although further academic verification is needed, this case shows that PQC could eventually be broken someday.

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The arrival of quantum computers also appears to be imminent. Professor Kim predicted, "According to Moore's Law, computational power doubles every 18 months. If this is applied to quantum computing, 100 qubits will become 100,000 qubits in 10 years," adding, "In 10 years, a 100,000-qubit quantum computer will be able to easily hack current cryptographic systems." He further said, "It could happen as soon as within 5 years, and at the latest, I don't think it will take more than 20 years."

According to Director Shim, to address potential vulnerabilities in structured lattices and ensure diversity in cryptographic methods, NIST reopened a call for new electronic signature algorithms in June last year.

Similarly, the Korean government is moving quickly to prepare for the transition to a PQC system by 2035. In January, it completed the selection of the "Korean Post-Quantum Cryptography (KpqC)" based on lattice-based algorithms and is promoting a pilot project to support the transition to PQC.

An official from the Ministry of Science and ICT said, "If the level of security differs between countries, problems may arise. Therefore, major countries are pushing for a transition to PQC by 2035, considering the commercialization timeline of quantum computers," adding, "Through pilot projects applying the selected algorithms to real life, we will verify their functionality in each sector and ensure a smooth transition by 2035."