"Quantum-resistant cryptosystems will be widely adopted in 5 years" Interview with Professor Damien Stehle

2022.08.09 09:45:05 | 2022.08.10 10:28:50

[Photo by Shin Hyun-gyu]이미지 확대

[Photo by Shin Hyun-gyu]

It was August 2016. The White House National Security Council (NSC) and the National Institute of Technology and Standards (NIST), a US government agency, issue a short memorandum of about 1,000 characters.”Current algorithms are vulnerable to attacks from large-scale quantum computers. The National Institute of Standards and Technology (NIST) has published a Federal Register Notice requesting comments on a proposed process to solicit, evaluate, and standardize one or more quantum-resistant public -key cryptographic algorithms.” And that was the start of the whole journey of global cryptographers.

Starting with this, the US government has been working to create standards for the cryptographic system to defend attacks with quantum computers. The encryption system currently called `RSA` (created in 1977 by three professors including Ron Ribest, Adi Shamir, and Leonard Adleman - RSA is named after the initials of the three professors) and a cryptographic system called `ECC` (a cryptographic system developed to overcome the limitations of RSA in 1985 - Algorithm using elliptic curves - Canadian company Certicom has intellectual property rights) are the most used now, but they all have vulnerabilities that quantum computers can easily dismantle. The White House faced this problem and started an attempt to set a completely new standard six years ago.

In the field of mathematics, a number of researchers have conducted various studies to establish a cryptographic system that defends threats from quantum computing skills (Post-Quantum Cryptography). And in May of this year, when about 6 years have passed since August 2016, President Joe Biden of the United States directly issued orders to "create a Pentagon encryption system that can block quantum computers." The order, signed by President Biden himself, reads: "Quantum computing poses significant risks to the economic and national security of the United States.The United States must seek to encourage transformative and fundamental scientific discoveries through investments in core QIS research programs.The United States must seek to foster the next generation of scientists and engineers with quantum-relevant skill sets, including those relevant to quantum-resistant cryptography.”

Two months later, on July 5, the US National Institute of Technology and Standards selected four criteria as a cryptographic system that can prevent attacks from quantum computers. When the mathematical algorithms (RSA, ECC) that kept the Internet world safe in the past were in danger of dying due to quantum computers, four superhero candidates were born to replace them. And two of the four main standards were proposed by a computer scientist from France. His name is Damien Stehlé. He is a professor at École Normale Supérieure de Lyon, France. For reference, according to the French education system, the Higher Normal School (Grandes Écoles) is the school that only selected elites could enter. After the general baccalaureate exam, students have to take another test through two years of preparation before the entrance. The interview with Prof. Stehlé was conducted with the help of CryptoLab CEO Cheon Jung-hee (Professor of Department of Mathematical Sciences, Seoul National University).

◆ Complete New Start of Cryptosystem

Professor Stehlé said, "My understanding about the plans of the US government, is that now that they start having standards of quantum safe crypto, and then these standards will be deployed forward on and progressively replace current ones.It`s similar to the decision in the mid-1999`s when they switched to ECC from RSA." The US National Institute of Technology and Standards announced that in 1999, 15 ECC-using elliptic curves were selected to replace RSA. After the US government`s decision, RSA began to be replaced by ECC in the 2000s, and today, ECC is more in the spotlight in areas such as the Bitcoin cryptosystem and the Internet of Things.

Researchers working with Professor Stehlé have proposed two cryptographic systems with quantum resistance (CRYSTALS-KYBER and CRYSTALS-Dilithium). It is a method that requires a computer to solve the computational problem of finding the nearest point from one point in the dimension of hundreds to thousands of units formed through a lattice pattern like a crystal to break the password. The two cryptosystems proposed by Professor Stehlé and his colleagues have the same principle as above, but `CRYSTALS-KYBER` is a method for encrypting a key, and `CRYSTALS-Dilithium` is a method for encrypting a digital signature. All of them are designed to present mathematical problems that are difficult to solve even with a quantum computer, which handles enormous operations that conventional semiconductor computers cannot. NIST said that the standards devised by Professor Stehlé and his colleagues were both selected for their strong security and excellent performance, and NIST expects them to work well in most applications. NIST was examining four candidates as quantum-resistant cryptosystems in the area of ​​generating cryptographic keys, and only CRYSTALS-KYBER proposed by Professor Stehlé and his colleagues was selected. Professor Stehlé said "it was a bit of a surprise”. It was even more surprising because of the remaining three cryptosystems that were eliminated, two of them had no large difference in performance and capacity from `CRYSTALS-KYBER proposed by Professor Stehlé et al.

◆ Global companies start testing Post-Quantum Cryptography

There are many companies around the world that make encryption systems that use ‘lattice’ patterns like Professor Stehlé. These include `ZAMA`, a company that develops homomorphic encryption using a lattice, `Dfinity`, a Swiss-San Francisco-based cryptosystem foundation, and `Algorand`, which was created by professors of MIT. In particular, `Algorand` recruited MIT Professor Chris Peikert, a world-renowned lattice based cryptography system researcher, in January 2021, and `Dfinity` also recruited cryptologist Jan Camenish from IBM in 2018. In Korea, a start-up `CryptoLab` using the lattice structure is also jumping into this global competition. The United States also does not insist on only the four criteria selected in July of this year as quantum-resistant cryptography standards. It has recently announced that it will re-compose a completely separate quantum-resistant cryptographic key project. Prof. Stehlé said, "It seems that the US government is willing to continue to change the standards that can defend quantum computers, if some unexpected problems are found."

Prof. Stehlé said that the scope of the encryption system proposed by himself and his colleagues is not just for the purpose of defending quantum computers, but can replace most of the encryption systems used today. He said that the use of post-quantum cryptosystems will be expanded, especially if quantum computers, which are not yet widely used, break through current security technologies. It can be used for various applications, from security systems on the web starting with https. In particular, national security could be a very important and sensitive area if a specific group that abused quantum computers can easily penetrate the existing defense security system. ECC encryption systems currently installed in many sensitive areas such as defense, aviation, space, and energy can be easily breached if quantum computers are used. "For the moment, there have been experimental deployments in order to test how much it costs, how much it consumes bandwidths and computer power and so on” he said. Pilot adoption for satellite data security or aircraft security is already active. For example, he added that `Airbus` is showing great interest in quantum-resistant digital signature systems” He also speculated, “Commercial deployments on large scale probably take the next five years, I would say.”

◆ Active research on cryptographic systems in Europe and Japan

The US’s move is just one example. A new technology called quantum computer is approaching as a security threat all over the world, including the European Union, the UK, Japan, Russia, and China. Thanks to this, mathematicians and cryptographers around the world have entered a full-fledged competition to create a cryptographic system that can defend quantum computers. Professor Stehlé said that as outstanding researchers in the field of mathematics are transferred to industry and companies, there is a shortage of people in the academic world to teach, and as a result, there is a shortage of cryptography education, which will cause further shortage. The war for securing cryptographers will inevitably intensify for the time being. A close example is that Japanese telecommunication company NTT is rapidly attracting cryptographers and intensifying research by establishing a research center in the United States. A company called `Sandbox AQ`, which is invested by Alphabet, the parent company of Google, has also recently brought in outstanding mathematicians in academia. In addition, startups such as Zama, Difitiny, and Algorand are also competing to attract outstanding talent from universities. Professor Stehlé said, "Many entities open research branches in the US. It`s a general phenomenon in the field. Many companies open many applications linking cryptocurrencies, blockchain, quantum security and government applications, military applications and so on. There is a significant flow from academics to industry.” Moreover, an important fact is that these companies all support fundamental mathematical research of talented people, said Prof. Stehlé and Prof. Cheon Jung-hee. This means that they are not only taking a shallow approach to the business opportunity that is right in front of them, but are thinking about a fundamental method that can change the game.

Professor Stehlé said that the winner of this battle for cryptography talent was the United States in the past, but now it is difficult to see that the United States will always lead the way as people can work anywhere now. As evidence, he said that many cryptosystem-related startups such as `Zama`, ‘Algorand’ are coming out in Europe, and places such as NTT in Japan are hiring cryptographers so hard. Professor Stehlé said there are also European strengths. In particular, strong collaboration between cryptographers exists in Europe. The success of Professor Stehlé’s team right now can be regarded as an example of a strong collaboration system among cryptography researchers in Europe. His team members from various countries such as France, Germany, the Netherlands, and Switzerland have researched together and created post-quantum cryptography standards. "In Europe, cooperation between cryptographers is very active," said Professor Stehlé . CEO Cheon Jung-hee expressed his disappointment, saying, "In Europe, cryptographers are actively conducting new research through cooperation, but in Asia, such a movement is not strong."

◆ Secret Sources of French Education that won 11 Fields Medals

In the interview with Professor Stehlé, we were able to get several implications for education, which is a fundamental way to lead in the global cryptography rush. First of all, France, the homeland of Professor Stehlé, is a mathematics powerhouse that has produced 11 people who have won the Fields Medal, which is called the Nobel Prize in mathematics. The `Fields Award` became famous in Korea as June Heo, a professor at Princeton University, received the award, and Professor Heo is the only Korean-born recipient. Professor Stehlé mentioned two reasons as to why France was able to become such a powerhouse in mathematics.

First, there is a free research atmosphere. In France, it is very difficult to get admission into the Grandes Écoles, but once you do, you have minimal learning and great freedom of research. Professor Stehlé said, "Higher Normal School selects people very picky and selects only the best," he said. "I think it`s an educational system to enable critical thinking," he added, "It is difficult to say that a person who solves problems well is a good researcher." In other words, the French Higher Normal School seeks not only a person who solves problems well, but also the person who chooses right problems. The judgment of choosing a valuable problem was regarded as a very important ability. Professor Stehlé said, “(Grandes Écoles’ philosophy) should be seen as a completely different mindset, in which students are not just given a problem to be studied, but that the process of finding the right problem is also a really important part of education" he said.

Second. There is a high respect for the science of `mathematics` in French society as a whole. Professor Stehlé said, "If a student is good in high school, then he will be told or he or she will be told to continue in mathematics, because it`s socially recognized as the most difficult topic and at the same time, the most prestigious topic. More than physics or computer science or even medical sciences.” He said that the best engineering institutions in France select students based on their mathematical abilities.

There was an article published in HRB in 2012, ‘Data Scientist: The Sexiest Job in the 21st Century.’ When asked if the title should be changed to `Cryptographer: The Sexiest job in France`, Professor Stehlé said, "Maybe." He said, "In the case of machine learning, there has been a tremendous movement of human resources from academia to companies after research has been conducted. Maybe the 2nd wave from academia to industry is happening in the cryptography field.”

On the other hand, professor Cheon at SNU (CEO of CryptoLabs) revealed his regrets for the Korean system, and envy for the French system. The reason why there are so many Fields Medals in France is that, especially in post-graduate education, they can choose to solve the problems they want to solve, and they are given the freedom and time to research to solve the problems. On the other hand, Korea still tries to teach curriculum-based, and it is a pity that relatively little time is devoted to free research. "People who are good at math are born at a similar rate in any country," he said. "But I think the important thing is how to educate people who are good at math after that."

By Shin Hyun-gyu

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