Performance Analysis and Multi-hop Protocols for Quantum Cryptography based on BB84

Quantum cryptography and its well-known application, quantum key distribution (QKD), promises unconditional security in data communications and is currently being deployed in commercial applications. However, there exist several challenges that concern QKD, such as secret key rate, distance, security and cost. The work of this thesis is at first developed by studying the best-know QKD protocol (BB84). The study provides performance analysis of the protocol over a quantum bit-flip channel in presence of eavesdropping, in terms of detection and false alarm probabilities, with an extension to the case of a generic quantum noisy channel. Finally, the problem of exchanging keys over long distances has been analized, providing a Multi-Hop protocol without using intercept-resend relays, and its extension to the case of a trusted node network, that exploits QKD only locally to establish secrets keys.