Quantum key distribution (QKD) is a popular introduction to quantum technologies used in education and public outreach, as very little background in quantum theory is needed and the practical applications are easily understood. There is considerably less exposure to the many real-world considerations of practical QKD, as access to the necessary hardware is quite limited. Here we describe a simple, simulation-based QKD project that can be implemented with only a minimal background in quantum concepts and programming. Students are assembled in small groups to develop an “Alice and Bob” protocol for securely distributing symmetric keys in a simulated noisy channel. Their protocol is then shared anonymously with another group who plays the role of Eve and attempts to steal as much secret key as possible. The adversarial aspect is popular with students, and the project itself provides a deeper understanding and appreciation for practical QKD.
Quantum key distribution (QKD) is a popular introduction to quantum technologies used in education and public outreach, as very little background in quantum theory is needed and the practical applications are easily understood. There is considerably less exposure to the many real-world considerations of practical QKD, as access to the necessary hardware is quite limited. Here we describe a simple, simulation-based QKD project that can be implemented with only a minimal background in quantum concepts and programming. Students are assembled in small groups to develop an “Alice and Bob” protocol for securely distributing symmetric keys in a simulated noisy channel. Their protocol is then shared anonymously with another group who plays the role of Eve and attempts to steal as much secret key as possible. The adversarial aspect is popular with students, and the project itself provides a deeper understanding and appreciation for practical QKD.
Quantum key distribution (QKD) is intended to produce cryptographic secret keys between two remote parties, usually called Alice and Bob. Even though QKD has been proven to be unconditionally secure against the eavesdropper, commonly called Eve, practical implementations of QKD may contain vulnerabilities that may lead to the generated secret keys being compromised. In order to detect the presence of the eavesdropper in the channel, in our proposal Alice introduces an interleaved sequence of decoy states which produce a characteristic distribution at Bob's station. Thus, in analyzing such distribution in presence and absence of the eavesdropper Eve, her activity in the channel is detected. This protocol doesn’t require changes at the quantum physical level, but it can be incorporated at the high software level.
Quantum technology, and especially quantum computing, is advancing rapidly. Our every-day secure communication infrastructure relies heavily on public key cryptography; unfortunately, many public key schemes are in fact insecure against quantum algorithms. Furthermore, adversaries who, today, capture information encrypted using classical key distribution systems, can wait and, as soon as quantum computers of sufficient power become available, they may decipher all previously captured information. While some new “post-quantum” public key systems are assumed to be secure against quantum computers, this is only an assumption and, even if the assumption remains valid, still results in systems that are less efficient for end-users than the more commonly used public key systems employed today. While the advent of quantum technology may seem detrimental to security, in fact, one may harness the power of quantum through quantum key distribution (QKD) for stronger security guarantees. Such QKD protocols allow two (or more) parties to establish a shared secret key, secure against an all-powerful adversary. Perhaps surprising is that QKD technology is already here both experimentally and commercially. This tutorial serves as an introduction to basic QKD along with QKD technology from a practical perspective. Quantum communication is a highly interdisciplinary field of research and one of the goals of this article is to introduce a larger set of researchers and practitioners to its study in the hopes of furthering its progress and eventual wide-scale adoption.
Quantum Key Distribution (QKD) is an innovative technology which exploits the laws of quantum physics to generate and distribute shared secret key for use in cryptographic devices. Quantum Key Distribution offers the advantage of ‘unconditionally secure’ key generation with the unique ability to detect eavesdropping on the key distribution channel and shows promise for high-security applications such as those found in banking, government, and military environments. However, Quantum Key Distribution is a nascent technology where realized systems suffer from implementation non-idealities, which may significantly impact system performance and security. In this article, we discuss the modeling of a decoy state enabled Quantum Key Distribution system built to study the impact of these practical limitations. Specifically, we present a thorough background on the decoy state protocol, detailed discussion of the modeled decoy state enabled Quantum Key Distribution system, and evidence for component and sub-system verification, as well as, multiple examples of system-level validation. Additionally, we bring attention to practical considerations associated with implementing the decoy state protocol security condition gained from these research activities.
Abstract Secure communication protocols are becoming increasingly important, e.g. for internet-based communication. Quantum key distribution (QKD) allows two parties, commonly called Alice and Bob, to generate a secret sequence of 0s and 1s called a key that is only known to themselves. Classically, Alice and Bob could never be certain that their communication was not compromised by a malicious eavesdropper. Quantum mechanics however makes secure communication possible. The fundamental principle of quantum mechanics that taking a measurement perturbs the system (unless the measurement is compatible with the quantum state) also applies to an eavesdropper. Using appropriate protocols to create the key, Alice and Bob can detect the presence of an eavesdropper by errors in their measurements. As part of the QuVis Quantum Mechanics Visualisation Project, we have developed a suite of four interactive simulations that demonstrate the basic principles of three different QKD protocols. The simulations use either polarised photons or spin 1/2 particles as physical realisations. The simulations and accompanying activities are freely available for use online or download, and run on a wide range of devices including tablets and PCs. Evaluation with students over three years was used to refine the simulations and activities. Preliminary studies show that the refined simulations and activities help students learn the basic principles of QKD at both the introductory and advanced undergraduate levels.
The counter-intuitive features of quantum mechanics make it possible to solve problems and perform tasks that are beyond the abilities of non-quantum (classical) computers and communication devices. The field of quantum information processing studies how we can achieve such improvements by representing information as quantum states.One of the early achievements of quantum information processing is the development of quantum key distribution (QKD). QKD protocols allow two participants (Alice and Bob) to achieve the classically-impossible task of generating a secret shared key even if their adversary is computationally unlimited.Unfortunately, the security promises of QKD are true only in theory; practical implementations of QKD deviate from the theoretical protocols, and many of these deviations give rise to practical attacks. In this research thesis, we study the security properties of various QKD protocols in many practical settings:First, we study practical security of semiquantum key distribution (SQKD) protocols, where either Alice or Bob is non-quantum (classical). Following practical security problems in previous SQKD protocols, we suggest a new SQKD protocol (the "Mirror protocol") which can be securely implemented, and we prove it robust and secure against a wide range of attacks (the "uniform collective attacks").Then, we study "composable security" of the first QKD protocol created by Bennett and Brassard (BB84). BB84 has its unconditional security proved against adversaries performing the most general attacks in a theoretical (idealized) setting; however, some security approaches do not prove "composable security", which requires the secret key to remain secret even when Alice and Bob actually use it for cryptographic purposes. We generalize an algebraic security approach for BB84, making it prove composable security of BB84 (and many variants of BB84) against the most general attacks.Finally, we analyze an important practical attack (named "Bright Illumination"), showing how it can be modeled as a theoretical "Reversed-Space" attack.Overall, all results aim to enhance our understanding on how to bridge the gap between theory and practice in various sub-fields of QKD, and they may help solve a major open problem in the field of QKD: constructing a realistic QKD implementation that can be proved truly and unconditionally secure against any possible attack.
Abstract The Quantum Key Distribution (QKD) is a well-researched secure communication method for exchanging cryptographic keys only known by the shared participants. The vulnerable problem of a secret key distribution is the negotiation and the transfer over an insecure or untrusted channel. Novel further developments of the QKD communication method are part of in-field technologies and applications in communication devices, such as satellites. However, expensive physical test setups are necessary to improve new application possibilities of cryptographic protocol involving components of quantum mechanics and quantum laws of physics. Therefore, optical simulation software can play a part in essential QKD simulating and further developing quantum-based cryptosystems. In the paper, the authors consider a feasible QKD setup based on the BB84 protocol to create a symmetric key material based on achieving a linear key rate via optical simulation software. The paper still provides two experimental architecture designs to use the QKD for a cryptosystem.