Current indoor wireless communication systems are shifting from classical microwave bands towards mm wave frequencies, whereas here the 60 GHz band is of special interest. Future systems are expected to work at even higher carrier frequencies in the sub-mm band beyond 300 GHz. In indoor wave propagation channels of such systems, diffraction occurs at a multitude of objects and hence must be considered for propagation simulations. Although the relevance of diffraction has been thouroughly studied at lower frequencies, it has not yet been analyzed methodically in the mm and sub-mm wave frequency range. This paper presents an extensive measurement campaign of the diffraction at objects like edges, wedges and cylinders for frequencies of 60 and 300 GHz. Different materials, realistic antennas as well as transmission through the objects are taken into account. Theoretical approaches are validated against the measurement results. Furthermore, shadowing of rays by persons is investigated and modeled with the help of diffraction. Finally, ray tracing is applied in an office scenario in order to evaluate the impact of diffraction on mm and sub-mm wave indoor channel characteristics.

Diffraction in mm and Sub-mm Wave Indoor Propagation Channels

This paper presents 28 GHz and 73 GHz millimeter-wave propagation measurements performed in a typical office environment using a 400 Megachip-per-second broadband sliding correlator channel sounder and highly directional steerable 15 dBi (30° beamwidth) and 20 dBi (15° beamwidth) horn antennas. Power delay profiles were acquired for 48 transmitter-receiver location combinations over distances ranging from 3.9 m to 45.9 m with maximum transmit powers of 24 dBm and 12.3 dBm at 28 GHz and 73 GHz, respectively. Directional and omnidirectional path loss models and RMS delay spread statistics are presented for line-of-sight and non-line-of-sight environments for both co- and cross-polarized antenna configurations. The LOS omnidirectional path loss exponents were 1.1 and 1.3 at 28 GHz and 73 GHz, and 2.7 and 3.2 in NLOS at 28 GHz and 73 GHz, respectively, for vertically-polarized antennas. The mean directional RMS delay spreads were 18.4 ns and 13.3 ns, with maximum values of 193 ns and 288 ns at 28 GHz and 73 GHz, respectively.

/pdf/28-ghz-and-73-ghz-millimeter-wave-indoor-propagation-3npcddjrpi.pdf

28 GHz and 73 GHz millimeter-wave indoor propagation measurements and path loss models

Wireless sensor networks (WSNs) are a prominent fundamental technology of the Internet of Things (IoTs). Rather than device-to-device communications, group communications in the form of broadcasting and multicasting incur efficient message deliveries among resource-constrained sensor nodes in the IoT-enabled WSNs. Secure and efficient key management is in many cases used to protect the authenticity, integrity, and confidentiality of multicast messages. This paper develops two group key establishment protocols for secure multicast communications among the resource-constrained devices in IoT. Major deployment conditions and requirements of each protocol are described in terms of the specific IoT application scenarios. Furthermore, the applicability of the two protocols is analyzed and justified by a comprehensive analysis of the performance, scalability, and security of the protocols proposed.

Group Key Establishment for Enabling Secure Multicast Communication in Wireless Sensor Networks Deployed for IoT Applications

In smart grid, various kinds of sensors have been equipped in smart meters to collect real-time consumption data and execute the instructions from the power management center, which leads to a more robust and customer-friendly grid system. However, a smart grid enables the two-way communication between the electricity supplier and users, which brings security challenges to the smart grid. In this paper, we propose a lightweight authenticated communication scheme for the smart grid, which ensures a secure two-way communication between the smart meters and the neighborhood gateway. Since in the proposed scheme, the smart meters only need to execute the bitwise exclusive-OR operations to encrypt collected usage data, and Lagrange interpolation formula is used to authenticate the sender; the transmitted messages can be real-timely authenticated. On the other side, the storage burden and communication cost of the smart meters can be significantly reduced. The security analysis shows that the messages transmission between the smart meters and the neighborhood gateway can be done in a confidential and authenticated manner. Furthermore, compared with other existing schemes, the performance analysis demonstrates that the proposed scheme has both lower storage and communication cost.

A Lightweight Authenticated Communication Scheme for Smart Grid

Distribution of cryptographic keys between devices communicating over a publicly accessible medium is an important component of secure design for networked systems. In this paper, we consider the problem of group key exchange between Electronic Control Units (ECUs) connected to the Controller Area Network (CAN) within an automobile. Typically, existing solutions map schemes defined for traditional network systems to the CAN. Our contribution is to utilize physical properties of the CAN bus to generate group keys. We demonstrate that pairwise interaction between ECUs over the CAN bus can be used to efficiently derive group keys in both authenticated and non-authenticated scenarios. We illustrate the efficiency and security properties of the proposed protocols. The scalability and security properties of our scheme are similar to multi-party extensions of Diffie-Hellman protocol, without the computational overhead of group operations.

/pdf/physical-layer-group-key-agreement-for-automotive-controller-3rvjtz4ig2.pdf

Physical Layer Group Key Agreement for Automotive Controller Area Networks

Key transfer protocols rely on a mutually trusted key generation center (KGC) to select session keys and transport session keys to all communication entities secretly. Most often, KGC encrypts session keys under another secret key shared with each entity during registration. In this paper, we propose an authenticated key transfer protocol based on secret sharing scheme that KGC can broadcast group key information to all group members at once and only authorized group members can recover the group key; but unauthorized users cannot recover the group key. The confidentiality of this transformation is information theoretically secure. We also provide authentication for transporting this group key. Goals and security threats of our proposed group key transfer protocol will be analyzed in detail.

/pdf/authenticated-group-key-transfer-protocol-based-on-secret-4yhm4pi2jh.pdf

Authenticated Group Key Transfer Protocol Based on Secret Sharing

In this paper, we propose a notion of contract signatures used in e-commerce applications. This scheme adopts digital multi-signature scheme in public-key cryptography to facilitate fair signature exchange over network. Security proof under the random oracle model of this modified signature scheme is include. This proposed solution allows two parties to produce and exchange two ambiguous signatures which are fully ambiguous for any third party (i.e. 1 out ambiguity). The combination of these two ambiguous signatures forms the contract signature. There is no “keystone” (i.e. a secret key used in the concurrent signature) of the signature. In case anyone releases the contract signature to a verifier, both signers bind to the contract signature.

/pdf/contract-signatures-in-e-commerce-applications-522q03c8n8.pdf

Contract Signatures in E-Commerce Applications

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Authenticated Group Key Transfer Protocol Based on Secret Sharing

Contract Signatures in E-Commerce Applications