Implements and compares Quantum Key Distribution (QKD) protocols such as BB84, E91, BBM92, and a proposed variant of BBM92. Implemented in Python using Qiskit, NumPy, and Matplotlib for simulation, analysis, and visualization. This code is inspired by Andrey Kardashin’s tutorial on the E91 Quantum Key Distribution Protocol, submitted to the Teach Me QISKit Award 2018 on GitHub and licensed under the Apache License 2.0. The original source code is available at: https://github.com/qiskit-community/qiskit-community-tutorials/blob/master/awards/teach_me_qiskit_2018/e91_qkd/e91_quantum_key_distribution_protocol.ipynb Modifications were made to ensure compatibility with the latest version of the Qiskit SDK. Additional code was developed based on this to simulate other QKD protocols, including BB84, BBM92, and a proposed variant of BBM92.