Description
Simulation codes of the article titled A New Scheme for Improving Channel-based Secret Key
Generation Rates
Abstract: Physical layer Secret key generation from the wireless channel is an emerging area of interest to provide confidentiality and authentication. One of the main challenges in this domain is to increase the length of the secret key while maintaining its randomness and uniformity. In this work, new dimensions for wireless channel-based key generation are proposed for orthogonal frequency division multiplexing (OFDM) systems. The novel perspective of the proposed work lies in the generation of key bits not only from the magnitudes of OFDM subchannels as it has conventionally been done but also from the number and positions/indices of those subchannels, whose channel gains are above the mean of the respective subblock. The effectiveness of the proposed algorithms is evaluated in terms of key generation rate and key mismatch rate. Additionally, a statistical test suite offered by the National Institute of Standards and Technology is used to evaluate the randomness of the generated key bits. It is shown in the simulation results that the involvement of the proposed dimensions can double the key generation rate compared to conventional algorithms.
Introduction:
Due to the broadcast nature of wireless communication, it
is vulnerable to eavesdropping and spoofing attacks [1]. The
conventional encryption-based solutions to tackle such attacks
may not be feasible in 5G and beyond heterogeneous wireless
networks due to the complexity of generation, management,
and sharing of secret keys among different entities. In order
to resolve such issues, physical layer key generation provides
an alternative to encryption-based methods by exploiting the
channel reciprocity property as a common source of random-
ness between communicating nodes. Also, the rich multipath
environment will ensure that the attacker will experience an
independent channel if it is half-wavelength apart from legit-
imate nodes. Besides, there is no need for any infrastructure
to distribute physical layer keys [2].
Physical layer key generation in multi-carrier systems such
as orthogonal frequency division multiplexing (OFDM) has
attracted significant interest due to increasing security and
pricey concerns. The major works in this direction are based on
the exploitation of received signal strength (RSS), amplitude
and phase of the channel impulse response (CIR)/channel
frequency response (CFR), and other feedback mechanisms
[3]. The authors in [4] exploit RSS for channel-based key gen-
eration in the OFDM system for both indoor and outdoor en-
vironments. In [5], subcarriers’ channel responses are utilized
in OFDM for secret key generation. Similarly, an experimental
setup for key generation from subcarriers’ channel responses
in OFDM is presented in [6]. In [7], multiple independent
phases are quantized for secret key generation in a multi-
carrier system. Likewise, the authors make use of phase change
of the time-varying channel frequency response corresponding
to OFDM subcarriers in [8]. In [9], OFDM subcarriers are
exploited along with precoding matrix indices for secret key
generation.
The above-mentioned conventional key generation-based
algorithms are effective methods for key generation. However,
they have certain limitations in terms of generating longer
keys while keeping the randomness and uniformity of the
key bits [3]. In order to enhance the key generation rate, we
proposed novel dimensions of key generation for multicarrier
communication systems in [10], where the indices of sub-
channel corresponding to best channel gains are exploited for
key generation along with the amplitude. We further build on
top of [10] by proposing the use of number, position, and
amplitude of subchannels in OFDM, which further enhances
the overall key rate compared to [10].
The main contributions of the proposed work are as follows.
• New dimensions of key generation are proposed, where
the number of subchannels in each subblock of the
OFDM block along with their position and amplitudes,
whose channel gains are above the mean of the subblock,
are exploited for a key generation. The proposed methods
are inspired by the concept of OFDM with subcarrier
number modulation (SNM) [11]. Particularly, the whole
OFDM block is divided into subblocks, where the number
of the subcarrier in each subblock is used similar to
OFDM SNM. However, here the number of subcarriers
is not chosen based on the data to convey information as
in OFDM-SNM but rather the number and positions, of
those subcarriers in each subblock whose gains are above
the mean of channel gains of each subblock, are used for
key generation.
• The proposed approaches can be used to provide confi-
dentiality and authentication against eavesdropping and
spoofing attacks in any multicarrier system such as
OFDM, OFDM-SNM [12], and OFDM-index modula-
tion. Besides, there is a potential to extend this work to
other domains such as space, time, and code.
• Several performance metrics, including key generation
rate (KGR) and key mismatch rate (KMR) are also
evaluated to get valuable insights about the proposed
algorithm. Moreover, a statistical test suite offered by the
National Institute of Standards and Technology (NIST) is
adopted to check the randomness of generated key bits.
The remaining parts of this work can be read from the publisher website at IEEE.
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