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Can Quantum Computer be a threat to public key cryptography?

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  • Can Quantum Computer be a threat to public key cryptography?


    Quantum computing has become a hot topic in recent years. Before tackling it, we need to take a look at digital computing.

    In digital computing, all information is stored as "0" and "1". The unit of information that we call "BIT" can be thought of as a lamp. The lamp can be either "On" or "Off". The lamp "On/Off" shows us the information. With a large number of these lamps, large volume of information can be stored in an array of "0/1" or "On/Off".

    Early computers really used lamps and therefore had high volume, low speed and high power consumption.


    With the invention of transistors in the middle of the last century, they replaced lamps. This made it possible to create PCs with much lower power consumption. With the advance of technology, the size of transistors has decreased day by day, making it possible to use very small smartphones.
    According to an empirical law called Moore's Law, the number of transistors that we can put at a certain level almost doubles every two years.This law has been valid for the past 50 years. However, there is a problem.

    On the one hand, as transistors become too small, classical physics loses its credibility and we actually have to get help from quantum physics.

    On the other hand, the electrical and magnetic behavior of small-scale quantum materials can be very different from larger materials. For example, a quantum particle can have a combination of all states instead of two states. In fact, the Quantum BIT (QUBIT) can store a probabilistic combination of "0" and "1" instead of just two modes of "0/1". As a result, transistors with these dimensions will exhibit strange behavior. However, they can store much more information.

    As mentioned earlier, QUBIT can be both "1" and "0" at the same time. This is called Superposition, which is one of the unique properties of quantum computers. Thus, when a quantum computer adds "0" to "1", it simultaneously adds "1" to "0", "1" to "1", and "0" to "0". If we can use this feature correctly, the computation speed and volume will be significantly increased.

    A stranger feature than Superposition is that QUBITs of quantum computers can be entangled together، intertwined and then influence each other from all over the world. These features are interesting in theory, but they are not easy to implement.

    Use cases

    Suppose there are a million products in the database and you want to find a specific product. On a regular computer, items must be checked one by one (First, second, third and so on). On the quantum computer we can examine all at once.

    In addition, the quantum computer can increase the speed of artificial intelligence learning and its ability to adapt to new information. For example, if you want to design a car wheel and want to make a change to make the car move better, a quantum computer will do it much easier.

    The next point is to break the code. If a regular computer wants to break the code, it should test all the combinations one by one, but the quantum computer can try all the combinations at once.

    Some of the challenges of using QUBIT

    1. QUBIT arrangement: How can we make these arrangements in very small dimensions?

    2. Temperature: At normal temperatures, QUBITs are not very stable and their state can randomly change. If we reduce the temperature too much to stabilize them, then they cannot be used in everyday life.

    3. programming: The basics of building a quantum computer program are unknown to us. There are some of the features like Superposition and Entanglement that we need to consider and apply in programming, but it is very difficult for us to understand their impact on programming. QUBITs should be treated as particles that are interconnected through some strings. This makes it easier to design the program and predict the behavior of the QUBIT. So, we need a higher level programming language that is like a game in which we open a lot of intertwined fishing lines to reach the fish. One can imagine that all of these strings are interconnected and that they are both rising, falling, and twisting. Drawing these strings together is a quantum program.

    Of course, it is important to note that advances in nanotechnology have partially overcome some of these challenges.

    Quantum computing and public key cryptography

    cryptocurrencies and other DLT-based projects utilize the algorithms like ECDSA and ECDH. Quantum computing is still in its early stage and it would need a lot of course until it attains the level which could wreck the crypto network. Why?

    Firstly, The production of quantum chips is extremely difficult. A sufficient number of QUBITs must be kept in a stable state for a sufficient period of time so that meaningful calculations can be carried out. For this, they must be shielded from all environmental factors as much as possible. Small temperature fluctuations or vibrations create a problem. Therefore, development is slow. Although IBM introduced the first commercial quantum computer at the beginning of the year, with its 20 QUBITs and record stability of 75 microseconds, it poses no real threat to the classic cryptosystems. To break Bitcoin requires at least 1,500 QUBITs.

    Secondly, According to Simon Benjamin, the Professor of Quantum Technologies in the University of Oxford,
    even if Google and IBM, as companies looking for Quantum Supremacy, can take a big step in their plans for quantum computers, this would not be a miracle. This is just one important step, but we cannot predict with certainty what computers will do. We still don't know how useful these computers can be, or what, for example, a 50-QUBIT computer can do. So, it's exciting but unclear. We have not yet reached the stage of telling others to give up their laptop and smartphone and buy a quantum computer.

    As a final point I should point out that there are already quantum-proof one-way signature methods that have already been implemented by some projects. Also, IBM and other well-known companies are developing cryptographic security measures to protect archived data against attacks by quantum computers.
    Last edited by crypto_enthusiast; 2 September 2019, 08:46 AM.