الفهرس 
IntroductionOnly 14 pages are availabe for public view
Abstract
Quantum Cryptography has been playing an important role in
communications after the reveal of vulnerabilities of classical channels.
The main aim of encryption is to guarantee the security of the messages
among communicators, without reducing the efficiency of communic ation
channel. The most popular idea was quantum key distribution which
unfortunately leads to the loss of lots of qubits since many of them have to
be discarded. In 2002, Quantum secure direct communication QSDC was
launched based on transmitting directly the secret messages without first
establishing a key to encrypt them. It does not require any additional
classical information in communications.
While most of the researches on channel security have
focused on point to point communication, little attention was given
to multi nodes networks. In this study, the possibilities of loopholes
in multi-sites networks using quantum secure direct communication
encryption protocols are analyzed. Several solutions are proposed.
Depending on the installed topology (linear, ring, star and partially
meshed) and on the distance between the nodes, a different solution
is proposed.
In this study as well, a complete modeling and simulation
has been done for a QSDC communication system using quantum
photonic simulator and compared to experimental results. Security
enhancements has been done by introducing decoy state function to
the system and dispersive compensation techniques to drive the
system to match practical fiber lengths which are required in
commercial systems.
Key words: Quantum Cryptography;Quantum Secure Direct
Communication; QSDC; multisite network; Entangled single photon pair;
Two step entanglement based protocol; Frequency coding scheme; Single
photon source; Decoy State protocol; Lumerical;