arXiv:1308.6437 · IEEE Transactions on Information Forensics and Security

Coding With Scrambling, Concatenation, and HARQ for the AWGN Wire-Tap Channel: A Security Gap Analysis

Marco Baldi, Marco Bianchi, Franco Chiaraluce

Published Feb 10, 2012• 128 citations

Abstract

This paper examines the use of nonsystematic channel codes to obtain secure transmissions over the additive white Gaussian noise wire-tap channel. Unlike the previous approaches, we propose to implement nonsystematic coded transmission by scrambling the information bits, and characterize the bit error rate of scrambled transmissions through theoretical arguments and numerical simulations. We have focused on some examples of Bose-Chaudhuri-Hocquenghem and low-density parity-check codes to estimate the security gap, which we have used as a measure of physical layer security, in addition to the bit error rate. Based on a number of numerical examples, we found that such a transmission technique can outperform alternative solutions. In fact, when an eavesdropper (Eve) has a worse channel than the authorized user (Bob), the security gap required to reach a given level of security is very small. The amount of degradation of Eve's channel with respect to Bob's that is needed to achieve sufficient security can be further reduced by implementing scrambling and descrambling operations on blocks of frames, rather than on single frames. While Eve's channel has a quality equal to or better than that of Bob's channel, we have shown that the use of a hybrid automatic repeat-request protocol with authentication still allows achieving a sufficient level of security. Finally, the secrecy performance of some practical schemes has also been measured in terms of the equivocation rate about the message at the eavesdropper and compared with that of ideal codes.

DOI: 10.1109/tifs.2012.2187515

Related papers

Increasing Physical Layer Security through Scrambled Codes and ARQ

Marco Baldi, Marco Bianchi, Franco Chiaraluce

We elaborate on the proposal of non-systematic channel codes on the AWGN wire-tap channel. Such coding technique, based on scrambling, achieves secure transmission with a small security gap between the authorized receiver (Bob) and the unauthorized one (Eve). In this paper, we show that, by implementing scrambling and descrambling on blocks of concatenated frames, rather than on single frames, the security gap between Bob and Eve can be further reduced. The usage of concatenated scrambling also allows to achieve security when Bob and Eve experience the same channel quality. In this case, the introduction of an ARQ protocol with authentication is needed.

arXiv:1109.0908IEEE International Conference on Communications workshopsJun 1, 201117 citations

Increasing physical layer security through scrambled codes and ARQ

Marco Baldi, Marco Bianchi, Franco Chiaraluce

We develop the proposal of non-systematic channel codes on the AWGN wire-tap channel. Such coding technique, based on scrambling, achieves high transmission security with a small degradation of the eavesdropper's channel with respect to the legitimate receiver's channel. In this paper, we show that, by implementing scrambling and descrambling on blocks of concatenated frames, rather than on single frames, the channel degradation needed is further reduced. The usage of concatenated scrambling allows to achieve security also when both receivers experience the same channel quality. However, in this case, the introduction of an ARQ protocol with authentication is needed.

Jan 1, 201120 citations

Security gap assessment for the fast fading wiretap channel

Nicola Maturo, Marco Baldi, Marco Bianchi +1 more

Using the error rate as a metric is useful for assessing the performance of actual transmission schemes from the physical layer security viewpoint. The security gap concept has been used over the additive white Gaussian noise channel as a practical measure for combined reliability and security. In this paper, the definition of security gap is extended to a wire-tap channel with fast fading. Our aim is to show that by introducing scrambling and error correction coding can significantly reduce the required quality difference between the channel of the authorized user and that of the unauthorized one.

May 1, 20136 citations

Communicating over wireless channels with information-theoretic secrecy

Xiaojun Tang

Wireless systems are susceptible to eavesdropping as an unwelcome result of the broadcast nature of the wireless medium. Fortunately, the wireless medium also provides endowments including the temporal dispersion, the capability of signal superposition and other properties, to facilitate defending against eavesdropping. The focus of the thesis is to provide schemes for utilizing these properties at the physical layer and their performance analysis from an information-theoretic secrecy perspective. The work is based on Wyner's results on the wire-tap channel, in which the transmission between two legitimate users (Alice and Bob) is eavesdropped upon by Eve. The secrecy level is measured by the equivocation rate at Eve. The system performance is measured by the secrecy capacity. This is the maximum rate at which a message can be sent from Alice to Bob, while constraining the equivocation rate at Eve equal to the communication rate, and thus ensuring that Eve cannot deduce any useful information asymptotically. First, the scenario where a secret message needs to be delivered to the intended receiver within a given delay constraint and without the knowledge of the channel state information (CSI) at the transmitter is considered. In particular, hybrid automatic retransmission request (HARQ) protocols are revisited for a block-fading wire-tap channel via a joint consideration of channel coding, secrecy coding, and retransmission protocols. Two secure HARQ protocols: a repetition time diversity (RTD) scheme with maximal-ratio combining, and an incremental redundancy (INR) scheme based on ratecompatible Wyner secrecy codes are analyzed via an outage-based formulation. The throughput of RTD and INR protocols under probabilistic outage requirements is derived. Asymptotic analysis and numerical computations are given to demonstrate both the benefits of HARQ protocols and the tradeoff between reliability and confidentiality in delay-constrained communications. Second, the effects of interference on information-theoretic secret communication is considered. More specifically, the wiretap channel with a helping interferer (WT-HI) is proposed and studied. Here, an interferer, which does not know the confidential message, helps in ensuring the secrecy of the message by sending independent signals. Achievable secrecy rates and upper bounds on the secrecy capacity are given for both discrete memoryless and Gaussian channels. Interference has conventionally been regarded as a harmful phenomenon that leads to decreasing the rate and the reliability performance of wireless systems. In this work, it is shown that interference can be exploited to assist wireless secrecy. Lastly, the problem of secret key generation over fading channels, in which there exists an additional authenticated, public and error-free feedback channel from Bob to Alice, is considered. A key generation scheme consisting of a communication phase and a key-generation phase is presented. The communication phase is based on layered broadcast coding, which adapts the decoded rate at Bob to the actual channel state without requiring CSI available at Alice. The key-generation phase is based on the messages decoded by Bob after the communication phase and the public feedback. The achievable secrecy key rate and the optimal power distribution over coded layers for maximizing the secrecy key rate are characterized. Theoretical and numerical results show that the broadcast approach outperforms the single-level-coding based approach significantly, and hence demonstrate the role of introducing self-interference in facilitating secret-key generation over slowly fading channels when transmit CSI is not available.

Jan 1, 20100 citations

Increasing physical layer security through reliability-based HARQ

Qinyu Zou, Bangning Zhang, Yanqing Ma +1 more

In this paper, we proposed a secure communication scheme based on Reliability-Based Hybrid Automatic Repeat reQuest (RB-HARQ) protocol over the additive white Gaussian noise (AWGN) wiretap channel. RB-HARQ protocol aims at retransmitting the unreliable bits required for the authorized user's (Bob) successfully decoding and minimizing the information leakage that may benefit to eavesdropper (Eve). The secrecy level in this paper is assessed through the bit error rate (BER) at both the authorized user (Bob) and eavesdropper (Eve). Therefore, we analyze the BER of our proposed scheme through theoretical arguments and simulations. Numerical results suggest that RB-HARQ protocol can significantly enhance the security performance of our communication system.

International Conference on Wireless Communications and Signal Processing (WCSP)Oct 1, 20162 citations

Physical Layer Security Using Scrambled BCH with Adaptive Granular HARQ

Azlan Abd Aziz, Mohammed Ahmed Magzoub Albashier, Azwan Mahmud +2 more

A dramatic increase in the number of devices that are connected to the wireless networks has seen many challenging issues.One of them is the security problem.Enhancement in physical layer security has shown promising results to improve these security issues in the existing wireless networks.This paper proposes a transmission technique based on scrambled Bose Chaudhuri Hocquenghem code with feedback to improve the physical layer security in wireless communication system.The security of the transmission system over a wiretap channel is investigated.Scrambling matrix is applied to the code word and a hybrid automatic repeat request (HARQ) protocol is used.In this paper, the security gap is used as a performance metric to measure the difference between the authorized and unauthorized channel.We find that the proposed technique results in smaller security gap compared to the conventional techniques.

Dec 23, 20220 citations