Introduction
Technology continues to grow at an unpredictable rate from artificial intelligence to cognitive computing. The security of the current and future technologies does not always align with the same trajectory. Cryptography has served well over the years in encrypting or concealing data of all types, but new cryptography has emerged to fit the new age of system attacks. Quantum cryptography has arrived in a big way. It is important to remember that the current protections used in the world of secure data have never reached a satisfactory point. This is due to the constant versions of vulnerabilities through the bending capabilities of technology. Quantum cryptography was first introduced by physicist Charles Bennet and computer scientist Gilles Brassard in 1984. The pair established the first protocol name BB84. Since the idea of Quantum cryptography, researchers have worked on various aspects to create a reliable product to scale the growing data security needs. It is an exciting field that deserves all the hype and recognition. This paper will discuss the aspects of quantum cryptography’s mechanical use of single photons, implementation, and how it can be used today.
Photons
Quantum cryptography, also known as quantum key distribution (QKD) is based on the laws of physics and attempts to guarantee the security of key distribution (Prawer & Aharonovich, 2016). The single-photon state is introduced by the process of electromagnetic field quantization inside a closed container or an open optical system (Roychoudhuri & Creath, 2005). Photon state is defined by its behavior when viewed through the optical beam splitter. This fascinating ability to maintain multiple states until viewed is a promising feature in the world of cryptography. To categorize a photon simply, it is the stuff light and radio waves are made of. Outside of its ability of multi-positional states, it is extremely lightweight, in fact, it is massless. QKD distributes single photons through a fiberoptic network that carries a cryptographic key.
Superposition
Protons have many unique abilities. One is the concept of superposition. This is the ability of a quantum system to be in multiple places at once until viewed. The notion of time and space are irrelevant when speaking of proton placement. To grasp this, think of the proton as not at any place until looked at. A team of physicists in the US and Germany has color-coded photons into two different colors. This representation of the quantum superposition of photons can help in connecting the different parts of a quantum information network (Johnston, 2016).
Implementation
The first protocol for quantum cryptography is BB84 named after the two creators and the year of its implementation. BB84 uses a rectilinear and diagonal basis for its secure communication protocol. Rectilinear basis refers to the horizontal and vertical polarization of a single photon (V & V, 2021). The diagonal basis refers to the polarization states of 45 and 135 degrees (V & V, 2021). The spin of the photon represents a value of 1 or 0 which is used in the encryption process known as quantum bits or qubits. The thought of binary in computer science is a rigid one. Thinking in terms of 1 or 0 is easy to comprehend; however, quantum computing is not quite as binary as traditionally thought. The qubits representing either 1 or 0 are deterministic on position and there are more than just two positional directions. In the BB84 protocol, light carries a photon with a generated polarized property known as the quantum basis (V & V, 2021). The quantum basis matches the binary values to produce a qubit that is used in generating the quantum key. This protocol is the first of a successful few. There have since been a dozen different protocols such as the E91 entanglement protocol and the most recent T12 decoy-state protocol. As quantum computing grows to a more widespread use the development and implementation of quantum cryptography needs to grow at the same rate.
Qubits
Quantum computing aims to take complicated computations that would take years to complete and solve them in a minute’s time or less. This directly relates to cryptography as mathematical algorithms are used to create encryption easily but are hard to decrypt. If there was a quantum computer that could solve the mathematical problem in minutes that would take a classical computer multiple years, then nothing is secure. Computer science must move beyond the classical 1 or 0 to affect the implementation of quantum computing power and memory capabilities. The qubit is the answer and provides a multi-positional approach to binary definition. The capabilities of the qubit are not completely known, and its behaviors remain inside theory; however, science does not have to be complete to use it.
Bloch sphere
Qubits are represented by a mathematical condition known as the block sphere named after Felix Bloch who won the Nobel Prize in 1962 (Sutor, 2019). Such calculations help generate a point of the quantum turn state of the photon. To determine what constitutes a 1 or a 0 the position or spin must be filtered. Take a choice of 0 the inverse of the cosine 1 to equal 0. If the position constitutes a 0 at this point the rotation of the ʐ axis is irrelevant. Viewed as a globe, each quantum state represented on the block spheres equator has an equal probability of producing either a 1 or 0. In the case of measuring latitude, the resulting 1 and 0 are the opposite or inversed approaches taken by the previous equator definition (Sutor, 2019). Simply put the qubit is a polarization state of the photon. As previously stated, the photon superposition does mean complications as some say, “the qubit is 1 and 0 at the same time.” The functionality provided by the physics of a photon brings a new binary form that provides capabilities yet to be discovered.
Current Applications
The application of QKD at the state of current knowledge seems to be completely secure. This is because if Bob sends Alice an encrypted message with a quantum key and Eve tries to capture the photon encryption the action will change the polarization of the key. When Bob and Alice compare quantum key attributes, they will see right away that Eve tried to break the encryption. The security is sound and provokes a desire to implement QKD protocols widely. Although quantum cryptography is used in a few numbers of corporations it is still not feasible for individual home use. The development of fully integrated light sources within a silicon photonics platform is not something everyone can buy at the local best buy. Like all technology used today, they were once thought of as ridiculously improbable. With a little physics, computer science, and time who knows what the applications of quantum computing and cryptography are?
Space Link Loss
QKD has been studied over the years and has grown in capabilities. One factor of study is the effects of space link losses. Space link loss is determined by the losses and fluctuation of the optical channel used to carry the photon. Scientists use classical studies conducted on satellite optical communications to infer solutions and build an analysis of beam waist. One aspect of quantum mechanics is that the atmosphere needs to be taken into consideration. Quantum signals moving in closed or free space links are directly affected. Studies of signals in the daylight compared to nighttime have shown this to be fact.
Quantum encryption algorithms
It is no dispute that quantum computing will break internet security as currently protected. One commonly used security protocol is RSA. RSA uses a public key to encrypt messages intended for the recipient and anyone who has access to that key can use it. The private key is used to decrypt the protected message. RSA is also used to secure purchase transactions and store information. In quantum computing, no one needs to steal or hack the private key. It can compute the solution of the private key from the public key quickly. In the case of the RSA protocol, a number that is the product of two primes is hard for an individual or classical computer to compute even if given hundreds or thousands of years (Sutor, 2019).
Algorithms come into play at the postprocessing phase of quantum encryption. There are several parameters for QKD to be strong or unbreakable such as the system’s clock rate, excess noise, quality, and speed of the algorithms (Pirandola et al., 2020). Not much is known about quantum algorithms; however, what is known is that cryptosystems using them are resistant to classical algorithms (Pirandola et al., 2020). There are a few algorithms that are used in other quantum applications that may provide more in the quantum cryptography field such as the Quantum Fourier Transform, phase estimation, and order finding algorithms (Abhijith et al., 2022). Just because there is quantum in front of the algorithm definition does not necessarily change the fundamentals. Take RSA for example, reducing factorization to period finding can be used in which an integer can be factored by using modular exponentiation (Abhijith et al., 2022). With quantum computing, the algorithm to encrypt did not change but rather the quantum system can compute the factorization algorithm with what is predicted to be less than a second.
Conclusion
This paper discussed the aspects of quantum cryptography’s mechanical use of single photons, implementation, and how it can be used today. Although evidence in this paper shows that quantum cryptography is possible it can not fully replace classical cryptography used today. For quantum cryptography to even start to implement widely quantum communication networks will need to be built, bandwidth will need to improve as there are theoretical limitations, and mechanics defined in physics needs to be understood more. Current cryptography has its weaknesses, that is a fact. This does not mean that communications over the internet are at large risk. For now, quantum computing and cryptography are a long way from affecting security. The real question is how much time is left in current cryptography. This is hard to say; however, as research continues its current trajectory it is feasible to reach a critical risk in a lifetime.
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