Cryptography is crucial to communication security. In 1984, a well-known QKD (quantum key distribution) protocol, BB84, was published by Bennett and Brassard. The BB84 Protocol was followed by the QKD protocols published by Ekert (1991) (E91) and Bennett (1992) (B92). Some authors proved security of the theoretical QKD protocols in different theoretical frameworks by defining security of QKD protocols differently. My argument is that the previous proofs of security are neither unique nor exhaustive for each theoretical QKD protocol, which means that proof of security of the theoretical QKD protocols has not been completed or achieved. The non-uniqueness and the non-exhaustiveness of the proofs will lead to more proofs. However, a coming “proof” of security of the theoretical QKD protocols is possible to be a disproof. The research by quantum mechanics in this paper disproves security of the theoretical QKD protocols, by establishing the theoretical framework of quantum mechanical proof, defining security of QKD protocols, establishing the quantum state of the final key of the theoretical protocols from their information leakages, and applying Grover’s fast quantum mechanical algorithm for database search to the quantum state of the final key to result in the Insecurity Theorem. This result is opposite to those of the previous proofs where the theoretical QKD protocols were secure. It is impossible for Alice and Bob to protect their communications from information leakage by stopping or canceling the protocols. The theoretical QKD keys are conventional and basically insecure. Disproof of security of the theoretical QKD protocols is logical.
Cryptography is crucial to communication security. In 1984, a well-known QKD (quantum key distribution) protocol, BB84, was published by Bennett and Brassard. The BB84 Protocol was followed by the QKD protocols published by Ekert (1991) (E91) and Bennett (1992) (B92). Some authors proved security of the theoretical QKD protocols in different theoretical frameworks by defining security of QKD protocols differently. My argument is that the previous proofs of security are neither unique nor exhaustive for each theoretical QKD protocol, which means that proof of security of the theoretical QKD protocols has not been completed or achieved. The non-uniqueness and the non-exhaustiveness of the proofs will lead to more proofs. However, a coming “proof” of security of the theoretical QKD protocols is possible to be a disproof. The research by quantum mechanics in this paper disproves security of the theoretical QKD protocols, by establishing the theoretical framework of quantum mechanical proof, defining security of QKD protocols, establishing the quantum state of the final key of the theoretical protocols from their information leakages, and applying Grover’s fast quantum mechanical algorithm for database search to the quantum state of the final key to result in the Insecurity Theorem. This result is opposite to those of the previous proofs where the theoretical QKD protocols were secure. It is impossible for Alice and Bob to protect their communications from information leakage by stopping or canceling the protocols. The theoretical QKD keys are conventional and basically insecure. Disproof of security of the theoretical QKD protocols is logical.
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.
It is generally accepted that quantum key distribution (QKD) could supply legitimate users with unconditional security during their communication. Quite a lot of satisfactory efforts have been achieved on experimentations with quantum cryptography. However, when the eavesdropper has extra-powerful computational ability, has access to a quantum computer, for example, and can carry into execution any eavesdropping measurement that is allowed by the laws of physics, the security against such attacks has not been widely studied and rigorously proved for most QKD protocols. Quite recently, Shor and Preskill proved concisely the unconditional security of the Bennett-Brassard 1984 (BB84) protocol. Their method is highly valued for its clarity of concept and concision of form. In order to take advantage of the Shor-Preskill technique in their proof of the unconditional security of the BB84 QKD protocol, we introduced in this paper a transformation that can translate the Bennett 1992 (B92) protocol into the BB84 protocol. By proving that the transformation leaks no more information to the eavesdropper, we proved the unconditional security of the B92 protocol. We also settled the problem proposed by Lo about how to prove the unconditional security of the B92 protocol with the Shor-Preskill method.
Quantum Key Distribution (QKD) is a technique that enables secure communication between two parties by sharing a secret key. One of the most well-known QKD protocols is the BB84 protocol, proposed by Charles Bennett and Gilles Brassard in 1984. In this protocol, Alice and Bob use a quantum channel to exchange qubits, allowing them to generate a shared key that is resistant to eavesdropping. This paper presents a comparative study of existing QKD schemes, including the BB84 protocol, and highlights the advancements made in the BB84 protocol over the years. The study aims to provide a comprehensive overview of the different QKD schemes and their strengths and weaknesses and demonstrate QKDs working principles through existing simulations and implementations. Through this study, we show that the BB84 protocol is a highly secure QKD scheme that has been extensively studied and implemented in various settings. Furthermore, we discuss the improvements made to the BB84 protocol to enhance its security and practicality, including the use of decoy states and advanced error correction techniques. Overall, this paper provides a comprehensive analysis of QKD schemes, focusing on the BB84 protocol in secure communication technologies.
Cryptography is being introduced to secure data. Through Classical Cryptographic technique, we can encrypt our data and secure secret key also. But classical cryptography is based on mathematical techniques where reversing one-way function is possible with sufficient computing power and time. So, Quantum Cryptography is introduced to overcome those drawbacks of traditional classical cryptography. It is based on the values of quantum mechanics and photon. Scientists and researchers have brought up a new key distribution protocol based on Quantum Cryptography is called Quantum Key Distribution (QKD) Protocol. The first QKD protocol BB84 was introduced by Charles Bennett and Gilles Brassard in 1984. After that several QKD protocols have been created. In this paper we have improved BB84 Protocol by removing the drawbacks of the existing algorithm towards Eavesdropping which may not be detected or disclosing large portion of secret key. Steps of the existing BB84 algorithm along with the modified one is described in detail with example and pseudo code. Limitations of BB84 and comparative study of both the existing and the improved one based on their security has been made and described in this current work.
Classical cryptographic systems are increasingly challenged by advances in computing power and new algorithmic techniques, particularly with the rise of quantum computing, which threatens the security of current encryption methods. This has spurred interest in quantum-resistant cryptography, aimed at creating algorithms that can withstand attacks from quantum computers. Traditionally, secure key transport over alternate channels has been a significant challenge, but quantum mechanics offers a solution. Quantum Key Distribution (QKD) is a revolutionary method for secure communication that leverages quantum principles. Unlike traditional methods, QKD provides unconditional security, with key security ensured by the laws of physics rather than computational difficulty. The BB84 protocol, introduced in 1984 by Bennett and Brassard, is a leading QKD scheme known for its simplicity and effectiveness in generating eavesdropping-resistant cryptographic keys. It facilitates secure key transport over alternate channels. This documentation aims to advance QKD security by practically implementing and analyzing the BB84 protocol. Through detailed theoretical analysis, simulation studies, and experimental validation, the practical impacts, and limitations of BB84-based QKD systems are examined. Additionally, a practical implementation of quantum key distribution using a sudoku key demonstrates the process's simplicity and effectiveness. These findings are expected to pave new paths in the field of cryptanalysis in the emerging Quantum Age.
Quantum key distribution (QKD), another name for quantum cryptography, is the most advanced subfield of quantum information and communication technology (QICT). The first QKD protocol was proposed in 1984, and since then, more protocols have been proposed. It uses quantum mechanics to enable secure exchange of cryptographic keys. In order to have high confidence in the security of the QKD protocols, such protocols must be proven to be secure against any arbitrary attacks. In this chapter, we discuss and demonstrate security proofs for QKD protocols. Security analysis of QKD protocols can be categorised into two techniques, namely infinite-key and finite-key analyses. Finite-key analysis offers more realistic results than the infinite-key one, while infinite-key analysis provides more simplicity. We briefly provide the background of QKD and also define the basic notion of security in QKD protocols. The cryptographic key is shared between Alice and Bob. Since the key is random and unknown to an eavesdropper, Eve, she is unable to learn anything about the message simply by intercepting the ciphertext. This phenomenon is beyond the ability of classical information processing. We then study some tools that are used in the derivation of security proofs for the infinite- and finite-length key limits.