Quantum computers.  What are the security issues

  • In the Coded Sword and Shield race, the Quantum Sword might gain an advantage soon. Then the security (including national security) of most security measures in use today will be called into question
  • The diagnosis of threats arising from the development of quantum technologies has contributed to more intensive work on “Shield” – a new way of building and transmitting cryptographic mechanisms
  • The security of quantum cryptography results, among other things, from the fact that anyone wishing to eavesdrop on transmitted information, as soon as they are noticed, will change it, which will not only distort the transmitted information, but also inform the sender and receiver of the fact of the eavesdropping.
  • These solutions are currently very limited in use by the armed forces and some financial institutions, but will likely become a new standard for encryption and data transmission in the near future (eg within the 6G network)
  • More such texts can be found on the main page of Onet.pl

Although hardly anyone is aware of this, the encryption of the information we transmit is one of the foundations of the interaction of modern societies. We use it to connect to websites, share files, or perform banking transactions. All this is due to the fact that it is possible to exchange information securely. In cryptography, as in other areas of life related to security, you can observe the “shield” and “sword” race – one party wants to keep its secrets and the other wants to get them. This race could reach a new level in the near future with advances at the intersection of quantum physics and information theory.

Physics and quantum technologies

Quantum mechanics is one of the most dynamically developing fields of physics – many Nobel Prizes have already been awarded for achievements in this field of knowledge. Thanks to these discoveries, for example, it is possible to create a laser. The use of Kantian mechanics may also affect other areas of human life and contribute to the creation of new inventions. Those that will affect the current way of exchanging digital information, especially those that we want to encrypt, seem to be of particular interest.

To explain the importance of quantum computers and quantum cryptography, it is necessary to point out several findings from quantum physics. It is worth starting with the fact that the behavior and locations of particles (such as photons or electrons) are random and non-deterministic – this is the fundamental discovery of quantum mechanics – predictability and statistics have replaced the predictability of conventional mechanics. In other words, elementary particles (such as electrons moving around the nucleus of an atom) fall into what are called superpositions – it is impossible to determine their position and momentum at the same time, until they are measured in different places at the same time. However, at the moment of measurement, the superposition state collapses, so that the particle’s position (but not its momentum, and vice versa) can be determined.

Another important discovery is the phenomenon known as “quantum entanglement” of particles, which means that when two objects (such as photons) interact in the past, the two objects retain a “memory” of their shared past. In other words, if the parameters are measured on one particle, the state of the other particle is known in advance, and interestingly, this effect may occur regardless of the distance between the two particles.

Quantum computers

Classical computers for information processing use a binary system, in which the “building blocks” are bits with a numerical value 1 or 0. Using a sequence of these bits, you can write any value, for example 8 bits (the so-called byte) that allows you to write numbers From 0 to 256, as a result, it allows you to encode all characters in the Latin alphabet, Arabic numbers and special characters. On the other hand, quantum computers are a completely different new type of device. To create it, it is necessary to move away from well-known and proven solutions in the field of classical geometry in favor of trying to use the properties that reality itself possesses at the subatomic level.

In 1981, A. Richard Feynman, the American pioneer in quantum electrodynamics, formulated the principles of quantum computers. Their primary property was to use, among other things, superposition, as the principle of operation of qubits (the smallest and indivisible units of quantum information), that is, the property of particles (such as electrons, photons or atomic nuclei) that allows them to be in different places at the same time, but With a different possibility. The advantage of qubits is that they can contain more information than conventional bits (they can also be quantum entangled with each other). Their computing power is growing exponentially (with 2 qubits we can have 4 bits of information, with 4 we can have 16 bits, etc.). However, to use this potential, algorithms are needed that are able to perform operations on these overlays, and finally calculate the result (traditional computers are still needed here) – these operations are repeated many times and the result is averaged.

It should be emphasized that quantum computers (so far) can be faster at solving a limited set of problems – those that require parallel processing of data. In other words, they will not replace traditional computers, at least for the foreseeable future. However, this narrow slice where quantum computers can become much faster than conventional machines is critical to modern cryptography.

In 2019, Google declared its quantum supremacy – the fact that a 53-qubit computer was capable of computing faster than today’s supercomputers. Instead of counting 10 thousand. A year, Google’s computer completed the task in 200 seconds. After the fact, IBM specialists pointed out an error in the data and showed that their supercomputer would need two and a half days to complete the task. Therefore, the indisputable quantum supremacy still had to wait. So far, Google technicians have solved the problem (they generated a string of random numbers), which, while important, is not important from a security perspective – they haven’t yet decrypted the encrypted message. However, there are many indications that it is only a matter of time before the efficiently used qubits speed up factorization, i.e. decomposition into prime numbers of keys commonly used today to encrypt information. In other words, in the Coded Sword and Shield race, the Quantum Sword might gain an advantage soon. The security of most security measures in use today will then be questioned.

Photo: Boykov / Shutterstock

Las Vegas quantum computer

“Quantum Sword”

Confidence in cryptographic algorithms currently in use is based on trust in the rules of mathematics. Nowadays, encrypting information with a 256-bit key sufficiently protects our communications against decryption – a supercomputer that would be able to perform billions of operations per second would take millions of years to decrypt. However, there is a risk that quantum computers could do such a task faster, provided they have the appropriate algorithms at their disposal. This algorithm was introduced in 1994 by Prof. Peter Shor, allows decomposing large natural numbers into primes, provided a sufficiently powerful quantum computer is used. So it seems only a matter of time before quantum computers equipped with proper algorithms become a serious national security challenge. This is due to the fact that, perhaps in a dozen years or so, the currently stolen information will be decrypted, although thanks to the use of quantum computers in the future, the secrets in it will be revealed. This fear generated the movement known as post-quantum cryptography.

“Quantum Shield”

Diagnosing the threats arising from the development of quantum technologies has contributed to more extensive work on the “shield” – a new way of building and transmitting cryptographic mechanisms (the keys used to secure information). Significantly, these efforts also use findings from quantum physicists (including principles of randomness and quantum entanglement). Implementing quantum security will make the connection secure again, because to decrypt it, not only the laws of mathematics will have to be broken, but the laws of nature themselves. The security of quantum cryptography results, among other things, from the fact that anyone wishing to eavesdrop on the transmitted information by mere observation will alter it, which will not only distort the transmitted information, but also inform the sender and receiver of the eavesdropping. These solutions are currently used to a very limited extent by the armed forces and some financial institutions, but they will likely become a new standard for encryption and data transmission in the near future (eg within the 6G network).

The introduction of such solutions will have both positive and negative consequences. Since it is the laws of physics, and not mathematical rules, that will protect the security of transmitted information, the brand of the supplier of communication equipment will not matter. In other words, devices of any production can be used in data transmission networks – it does not matter whether the manufacturer deliberately inserted some vulnerability in the code that would allow eavesdropping, thanks to the fact that no eavesdropping in quantum cryptography can not be done disclosed.

In addition, with the first successes, work on the use of, among other things, quantum entanglement for the purposes of data exchange. In 2020, Chinese scientists were able to link quantum memories together over a distance of 50 kilometers. At the same time, it should be noted that currently secure quantum communication is possible (using photons) over short distances over optical fibers. This situation could improve because another team of scientists was recently able to transmit simple information over 600 km. This performance can be improved by placing a signal transducer in space. Then, using satellites, the signal (the entangled pairs of photons that make up the key) can be sent across the entire planet’s space, and then the dream of a crack-resistant Internet can become a reality.


Today, quantum computers are at a similar stage of development as the personal computers of the 1970s, and like artificial intelligence, they can perform very narrowly specialized tasks. However, it is likely, in terms of cryptography, that the race between “sword” and “shield” can certainly be decided in favor of “shield”. However, you have to be patient. We still have to wait for the final effects. After the hype around quantum technology, there will certainly be a period of disappointment, but then (maybe not 10 years ago) there was a period of standardization and efficient applications that would deliver both a secure quantum internet and quantum computers under this roof.

The article was published in collaboration with the Circulation Portal, the Knowledge Portal, and the Social Engagement Portal as part of the Jagiellonian University Strategic Program Excellence Initiative.


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