This paper focuses on the implementation and comparative analysis of two widely studied QKD protocols. The BB84 and E91 protocols are security measures that were devised back in the 1980s and 90s by experts like Charles Bennett and Ekaterina S. Ekert. This paper demonstrates with Qiskit protocol implementation documentation and simulation results together with extensive security analysis how BB84 and E91 protocols can be utilized through an open-source quantum computing framework developed by IBM. This paper aims to examine the BB84 and E91 protocol resistance to eavesdropping invasions while testing their performance across different communication ranges. We utilize quantum superposition to encode information into qubits during BB84 protocol implementation which allows us to simulate an intercept-resend attack to determine its vulnerability. Research shows that BB84 provides simpler execution yet suffers from more eavesdropping attacks especially at extended distances through increased error rates from interception methods. E91 protocol achieves detection of eavesdropping by distributing entangled qubits between two parties so measurements of those qubits reveal tampering through their outcome correlations. Our experimental findings confirm that E91 delivers enhanced security capabilities through its ability to keep errors minimal across longer distances thus demonstrating resistance against distance-related threats. The comparative analysis underscores the strengths and limitations of each protocol. BB84, despite its simplicity and ease of implementation, shows diminished security over longer distances. E91, which uses the non-local properties of entangled qubits, offers enhanced protection for long-distance communication, making it a more practical choice for robust QKD systems.
This paper focuses on the implementation and comparative analysis of two widely studied QKD protocols. The BB84 and E91 protocols are security measures that were devised back in the 1980s and 90s by experts like Charles Bennett and Ekaterina S. Ekert. This paper demonstrates with Qiskit protocol implementation documentation and simulation results together with extensive security analysis how BB84 and E91 protocols can be utilized through an open-source quantum computing framework developed by IBM. This paper aims to examine the BB84 and E91 protocol resistance to eavesdropping invasions while testing their performance across different communication ranges. We utilize quantum superposition to encode information into qubits during BB84 protocol implementation which allows us to simulate an intercept-resend attack to determine its vulnerability. Research shows that BB84 provides simpler execution yet suffers from more eavesdropping attacks especially at extended distances through increased error rates from interception methods. E91 protocol achieves detection of eavesdropping by distributing entangled qubits between two parties so measurements of those qubits reveal tampering through their outcome correlations. Our experimental findings confirm that E91 delivers enhanced security capabilities through its ability to keep errors minimal across longer distances thus demonstrating resistance against distance-related threats. The comparative analysis underscores the strengths and limitations of each protocol. BB84, despite its simplicity and ease of implementation, shows diminished security over longer distances. E91, which uses the non-local properties of entangled qubits, offers enhanced protection for long-distance communication, making it a more practical choice for robust QKD systems.
Abstract This paper investigates practical performances of the Ekert 91 protocol (E91) for future secure quantum networks. To seek future possible improvement, we investigate the important different principles of E91 and Bennet-Brasard (BB84) protocols. We perform a series of computer simulations to evaluate the performances of them and investigate the practical parameters. Furthermore, we simulate the E91 protocol using real-world practical scenarios involving eavesdropping and quantum channel errors. We present two scenarios: (1) the performance with eavesdropper interception under a perfect channel and (2) the performances with eavesdropper interception combined with channel errors. We found that: (i) the E91 protocol produces fewer keys compared to the BB84 protocol but does not require verification between two parties, (ii) the E91 protocol enhances security due to the utilization of Clauser, Horne, Shimony, and Holt (CHSH) inequality, and (iii) both eavesdropper and channel errors can impact the less production of keys obtained during the keys production.
Quantum cryptography is anticipated to drive substantial advancements in cybersecurity. The impending arrival of quantum cryptography compromises current encryption methods, possibly compromising the effectiveness of traditional key management-based security protocols. One fundamental Quantum Key Distribution (QKD) protocol, BB84, encounters challenges when operating with fewer Quantum bits (Qubits) and bases that only support up to 8 Qubits. This limitation weakens the system’s security, making brute force, intercept, and resend attacks less challenging. Consequently, this study proposes a method to enhance the security of the BB84 protocol, to reduce susceptibility to attacks and eavesdropping. The improved BB84 protocol utilizes 9, 12, and 16 quantum bits along with two, and three bases to significantly bolster security. This allows authorized parties to eliminate the use of compromised keys. Additionally, the study implements the E91 QKD protocol utilizing the Entanglement Pair Generation (EPR) method to produce secure keys. While the existing E91 protocol ensures security through Bell’s theorem and Bell’s inequality, it overlooks the impact of noise, leading to inaccuracies in eavesdropper detection. To address this, the study introduces an additional security measure. Whenever an eavesdropper attempts to measure the quantum state, the proposed E91 protocol collapses its state from$\vert 10\rangle to\vert 11\rangle ,settingthefirstQubitto\vert 1\rangle andtheotherQubitto\vert 0\rangle $, thus providing the eavesdropper with incorrect information, accompanied by a phase angle of$15\pi $/8. This leads to a misconception, preventing eavesdroppers from obtaining useful details about transferred quantum states. Additionally, considering that the proposed E91 protocol relies on entangled particles and utilizes double Qubit gates, which are inherently noisier than single Qubit gates and more susceptible to quantum decoherence, this study employs error mitigation techniques during the final measurement to predict outcomes more efficiently.
Quantum Key Distribution (QKD) is a ground-breaking solution to secure communication that uses fundamental quantum mechanics principles to allow for the exchange of cryptographic keys with provable security. BB84 and E91, two of the first and most significant QKD systems, presented two different approaches to using quantum characteristics to prevent eavesdropping and maintain confidentiality. A brief literature review of these two fundamental protocols is presented in this paper. Bennett and Brassard created the BB84 protocol in 1984. It uses polarized photons and detects interception using the uncertainty principle. On the other hand, Bell's theorem and entangled photon pairs are used in the E91 protocol, which was first presented by Ekert in 1991, to guarantee the integrity of the shared key. Each protocol's theoretical foundations, methods of implementation, and relative benefits has been explored in addition to how they have influenced contemporary quantum cryptography systems. This paper attempts to give a basic understanding of QKD and its early advancements by examining the similarities and differences between BB84 and E91.
Quantum cryptography offers possibilities to distribute keys securely by relying on the principles of quantum mechanics. This paper presents repeatable simulations of two well-known quantum key distribution protocols, BB84 and E91, and examines how eavesdropping, noise, and transmission losses affect their security. The simulations are carried out using the Qiskit framework. A theoretical analysis of the expected quantum bit error rate (QBER) under ideal conditions and during an intercept–resend attack is included. The Clauser–Horne–Shimony–Holt (CHSH) parameter is also evaluated for the entanglement-based protocol. The results show error rates close to zero without attack, an increase to about 25\% under eavesdropping, and reduced correlations in the presence of attacks or losses. For the E91 protocol, the CHSH parameter exceeds the classical bound (S >2) in the entangled scenario and drops below the classical limit (S <= 2) in the attack case.
The rapid advancement of quantum computing poses a significant threat to classical cryptographic systems that form the backbone of modern digital security.Algorithms such as RSA and ECC, which rely on the computational difficulty of integer factorization and discrete logarithm problems, become vulnerable to quantum attacks, particularly Shor's algorithm.This project presents a comprehensive Quantum Key Distribution (QKD) Simulator that implements the BB84 and E91 protocols using IBM's Qiskit quantum computing framework, providing an interactive platform for understanding, simulating, and analyzing quantum-safe key exchange mechanisms.The simulator features a full-stack architecture with a FastAPI backend powered by Python and Qiskit for quantum circuit execution, and a React 19 frontend with TypeScript for interactive visualization.The BB84 protocol implementation supports configurable qubit counts, multiple measurement bases (Z, X, and Diagonal), Eve's intercept-resend attack simulation with adjustable interception rates, and Quantum Bit Error Rate (QBER) calculation with a security threshold of 8.5%.The E91 protocol implementation uses entangled Bell state pairs with configurable measurement angles, CHSH inequality violation testing for quantum security verification, and reverse gate anti-eavesdropping mechanisms.Additionally, the system includes an AES encryption module that uses quantum-generated keys from BB84 and E91 simulations to perform AES-128, AES-192, and AES-256 encryption, with privacy amplification for keys shorter than the required length.A simulation history system with SQLite and PostgreSQL support enables experiment tracking, comparison, and analysis.The project demonstrates the practical application of quantum mechanics principles to cryptographic security and serves as an educational tool for understanding the transition from classical to quantum-safe cryptography.
Quantum Key Distribution (QKD) provides an innovative approach for secure communication by utilizing the principles of quantum mechanics. Among various QKD protocols, the BB84 protocol remains the most widely studied and implemented due to its simplicity and theoretical security guarantees. However, practical implementations of BB84 are vulnerable to several eavesdropping attacks and channel imperfections. This paper presents a comprehensive study on the detection and analysis of eavesdropping attacks in the BB84 protocol. The work focuses on common attacks such as intercept-resend attack, photon-number splitting attack, Trojan horse attack, and phase-covariant cloning attack. The effect of these attacks on Quantum Bit Error Rate (QBER) is analyzed in detail. Simulation-based observations are discussed to demonstrate how QBER increases under malicious interference. The study further explores statistical methods for detecting eavesdropping and examines practical countermeasures including decoy states, privacy amplification, and error correction techniques. The paper concludes that BB84 remains robust against eavesdropping when proper detection and mitigation mechanisms are employed.