The need for secure transmission in the fields of banking and defense has led to the interest in quantum cryptographic protocols which are theoretically more secure than any classical cryptographic protocol. However, the current implementations of the quantum cryptographic protocols have weaknesses. The main goal of this work is to find ways to strengthen quantum cryptographic protocols by using new implementation schemes. We present a method to improve the randomness of the sequence of polarization states used in BB84, the two-stage and the three-stage protocols. An analysis of quantum cryptography in the presence of noise is given. We also study a variant of the three-stage protocol where the intensity of the photons is tracked. We have developed a further improvement to this protocol where the state of the photons is also estimated.
The need for secure transmission in the fields of banking and defense has led to the interest in quantum cryptographic protocols which are theoretically more secure than any classical cryptographic protocol. However, the current implementations of the quantum cryptographic protocols have weaknesses. The main goal of this work is to find ways to strengthen quantum cryptographic protocols by using new implementation schemes. We present a method to improve the randomness of the sequence of polarization states used in BB84, the two-stage and the three-stage protocols. An analysis of quantum cryptography in the presence of noise is given. We also study a variant of the three-stage protocol where the intensity of the photons is tracked. We have developed a further improvement to this protocol where the state of the photons is also estimated.
The paper presents the implementation of a quantum cryptography protocol for secure communication. As computing power increases, classical cryptography and key management schemes based on computational complexity become increasingly susceptible to brute force and cryptanalytic attacks. Current implementations of quantum cryptography are based on the BB84 protocol, which is susceptible to siphoning attacks on the multiple photons emitted by practical laser sources. The three-stage protocol, whose implementation is described in this paper, is a departure from conventional practice and it obviates some of the known vulnerabilities of the current implementations of quantum cryptography. This paper presents an implementation of the three-stage quantum communication protocol in free-space. To the best of the authors' knowledge, this is the first implementation of a quantum protocol where multiple photons can be used for secure communication.
The paper presents the implementation of a quantum cryptography protocol for secure communication. As computing power increases, classical cryptography and key management schemes based on computational complexity become increasingly susceptible to brute force and cryptanalytic attacks. Current implementations of quantum cryptography are based on the BB84 protocol, which is susceptible to siphoning attacks on the multiple photons emitted by practical laser sources. The three-stage protocol, whose implementation is described in this paper, is a departure from conventional practice and it obviates some of the known vulnerabilities of the current implementations of quantum cryptography. This paper presents an implementation of the three- stage quantum communication protocol in free- space. To the best of the authors' knowledge, this is the first implementation of a quantum protocol where multiple photons can be used for secure communication.
Most current research on quantum cryptography requires transmission and reception of single photons that creates severe implementation challenges and limits range. This paper argues for the development of threshold quantum cryptography protocols in which the system is secure so long as the number of photons being exchanged between Alice and Bob is below a specified threshold. We speak of a (p-k-n) threshold system where if the number of photons exchanged is less than p, the system is completely secure, when it is between p and k, the system is partially secure, and when it exceeds k, the system is insecure. The BB84 protocol is (1-1-1) whereas the three-stage protocol appears to be (p-4p-n), where p is the least number of photons necessary to determine the polarization state of identically prepared photons. New quantum cryptography systems should be sought that provide greater flexibility in the choice of p and k.
Quantum cryptography, the principles of which are based on classical mechanics laws, solves exceptionally the issue of key distribution in classical cryptography. BB84, the first quantum key distribution created by Charles Bennett and Gilles Brassard in 1984 offers unconditional security and allows the transmission of a key with the length equal to the length of the message. According to Vernom, using the key with the above feature once together with an encryption algorithm leads to the formation of a most secure cryptographic system. The paper presents a method for improving the BB84 quantum protocol, using ten states of polarization, quantum memory and direct communication in both directions. The implementation of both the proposed method and the BB84 protocol was done through a C# application.
Currently, theoretical and experimental work in the field of quantum cryptography is being carried out in many research centers around the world. Over the past two decades since the start of active research, many quantum cryptographic protocols have been proposed, a significant number of laboratory experiments have been performed on their practical implementation, important work has been done to prove the resistance of the proposed protocols to certain types of attacks, and the first commercial quantum key distribution systems have been developed. However, there are still many tasks and problems in the field of quantum cryptography, the solution of which is of great scientific and technical importance. So, in particular, such a promising direction as quantum protocols for direct secure communication requires further development, allowing, under certain conditions, to transfer secret information without encryption, both between two and between a large number of users. Currently, such protocols have been developed using two-and three-particle entangled states, but there are almost no similar protocols with entangled states of a larger number of qubits that do not require large quantum memory for their implementation and, at the same time, have a large information capacity. Therefore, the development of new quantum direct secure communication protocols with increased information capacity, the analysis of their resistance to attacks, as well as the determination of the best protocols according to the criteria of resistance and information capacity.
Information security is increasingly important as society migrates to the information age. Classical cryptography widely used nowadays is based on computational complexity, which means that it assumes that solving some particular mathematical problems is hard on a classical computer. With the development of supercomputers and, potentially, quantum computers, classical cryptography has more and more potential risks. Quantum cryptography provides a solution which is based on the Heisenberg uncertainty principle and no-cloning theorem. While BB84-based quantum protocols are only secure when a single photon is used in communication, the three-stage quantum protocol is multi-photon tolerant. However, existing analyses assume perfect noiseless channels. In this paper, a multi-photon analysis is performed for the three-stage quantum protocol under the collective-rotation noise model. The analysis provides insights into the impact of the noise level on a three-stage quantum cryptography system.