| dc.description.abstract | In this thesis, a new practical method to realize one-time pad perfect secrecy for wireless
communication is presented. Most commonly used security methods are based on cryp- tographic
techniques employed at the upper layers of a wireless network. These methods basically rely on the
computational hardness of some mathematical problems. This com- putational complexity is vulnerable
in nature due to fast-growing computational power of hardware technology, yet not taking into
account the revolution of Quantum computing in further future. Another core problematic issue
exists in symmetric security systems; there is a deadlock between securing the channel and
establishing the shared key. We need the key for securing the channel, on the other hand, for
sharing the key we need a secure channel.
To address such vulnerabilities, Physical Layer Security (PLS) has been widely studied in recent
years. PLS schemes build on the idea of turning unpredictable and random wire- less channel
characteristics into a source for information-theoretic security. Information- theoretic security
itself, relies on Shannon’s pioneer work . Shannon, inspired by one-time pad, also known as Vernam
cipher, theoretically showed that the only unconditional per- fect secrecy system is a one-time pad
with a key at least as random as the plaintext, i.e., a system that uses a different random key to
cipher any new plaintext. In PLS key genera- tion methods, legitimate parties alternately send
probe signals and estimate Channel State Information (CSI) of common random channel and then
convert enough amount of these estimates to secure shared keys. To achieve perfect secrecy, the key
generation methods must meet the key randomness and Key Generation Rate (KGR) requirements of
their specific cryptographic applications.
In this research a new practical system for achieving unconditional perfect secrecy is presented.
Our system uses channel phase as the probing parameter to fully benefit from its uniform
distribution over [0, 2π]. It also uses an encryption method based on modulo-
2π addition of phase values which is the perfect counterpart of XOR addition in binary one-time
pad. Moreover, by intentionally perturbing the wireless channel in vicinity of the transceiver
antenna based on RF-mirrors structure, it produces different random phase values in each channel
probing, much faster than the inherent channel variation would do, resulting in dramatically higher
KGR than any wide-band PLS scheme presented so far and realizing true perfect secrecy. Most
importantly, the focus of this research is a detailed practical algorithm for implementing the
system as well as empirical results which makes
our system the first channel-phase-based PLS scheme implementation, reported so far. | en |
