MIMO-Based Secret Key Generation Strategies: Rate Analysis

MIMO-Based Secret Key Generation Strategies: Rate Analysis

Kan Chen (Kansas State University, Manhattan, KS, USA) and Bala Natarajan (Kansas State University, Manhattan, KS, USA)
DOI: 10.4018/IJMCMC.2014070102


Over the last decade, physical layer secret key generation (PHY-SKG) techniques that exploit reciprocity of wireless channels have attracted considerable interest among researchers in the field of wireless communication. Compared to traditional cryptographic methods, PHY-SKG techniques offer the following advantages: a computationally bounded adversary does not need to be assumed; PHY-SKG avoids the requirement of key management, and secret keys can be dynamically replenished. Additionally, PHY-SKG can enhance existing security schemes because it operates independently of higher layer security schemes. However, a key drawback of PHY-SKG is low secret key generation rate (SKGR), a critical performance metric. Therefore, the role of advanced network technologies (e.g., multiple input multiple output (MIMO) and cooperative MIMO) must be explored to enhance SKGR. This paper describes how MIMO and cooperative MIMO techniques can enhance SKGR.
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Avoidance of eavesdropping, message modification, and node impersonation from unintended recipients is difficult because of the broadcast nature of wireless communication (Molisch, 2010). Adversarial users are modeled as unauthorized users that attempt to extract information from legitimate users. To protect the confidentiality, integrity, and authenticity of transmitted data, secrecy at physical layer (PHY-layer) has recently attracted significant interest among researchers. Traditional key-based enciphering techniques are limited by key distribution (Wang, Xu, & Ren, 2011); computational complexity (Maurer, 1993), etc .Therefore, security techniques on physical layer has garnered attention after the distinguished work by Shannon (Shannon, 1949). Following Shannon's fundamental work on information-theoretic security, Wyner introduced a new wire-tap channel model in (Wyner, 1975). Based on the assumption that the wiretap channel is a probabilistically degrade version of the main channel (Mukherjee A., Fakoorian, Huang, & Swindlehurst, 2014), the object of Wyner’s keyless security scheme at PHY-Layer is to maximize the transmission rate of main channel while minimizing the amount of information leaked to wiretap channel (wiretapper). Thereafter, Maurer presented a strategy that allows joint development of secret keys between transmitter and receiver with the help of a public and error-free feedback channel (Maurer, 1993). Therefore, secret keys can be extracted between communication parties by exploiting the common randomness in wireless channel (reciprocity). Recently, Radio Frequency (RF) fingerprinting technique is proposed by PHY-Layer security community as an additional layer for wireless device. Transmitters are identified by examining their unique transient characteristics. A receiver can challenge a user to prove its unique identity to further enhance the security level of wireless communication. Therefore, the three main thrust areas in PHY-Layer security research are (1) keyless security based on the work of by Wyner (Wyner, 1975) (R. Liu, 2013) (Rodrigues, 2006); (2) PHY-layer secret key generation (PHY-SKG) following the work of Shannon and Maurer (Maurer, 1993) (Ahlswede & Csiszar, 1993) (Csiszar & Narayan, 1997); and (3) RF fingerprint (Rehman, Sowerby, & Coghill, 2014) (Rehman, Sowerby, & Coghill, 2012) (Rehman, Sowerby, & Coghill, 2014). In this paper, we mainly focus on the PHY-SKG problem. Secret keys are generated by common randomness that sources extract from channels between parties in a wireless communication system. Eavesdroppers experience independent physical channels from legitimate users as long as they are a few wavelengths away from legitimate nodes (Lai & Ho, 2012), as is common in wireless networks. Therefore, keys are secure with an information theoretic guarantee (Bloch M., Barros, Rodrigues, & McLaughlin, 2008). Compared to a classical secret key generation (SKG) algorithm such as Diffie-Hellman protocol, PHY-SKG technique has the following advantages: (1) a computationally bounded adversary does not need to be assumed (Wang, Su, Ren, & Kim, 2011); (2) PHY-SKG does not require key management, which is a challenging topic in traditional key generation schemes (Sayeed & Perrig, 2008); (3) secret keys can be dynamically replenished since wireless channels vary over time (Shiu, Chang, Wu, Huang, & Chen, 2011). Additionally, PHY-SKG can be used to enhance existing security schemes because it can be implemented independently of higher layer security schemes (Mukherjee A., Fakoorian, Huang, & Swindlehurst, 2014).

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