THz Spectrum a Boon and/or Bane for NextGen Secure Communication

For detailed information refer the Paper: Link

Source: https://roh9singh.com/my-blog

With each generation of wireless communication, we have seen improvements in data rates, security, and reliability [1]. This trend will be continued in the future generations, as shown in Figure 1. The primary users of wireless communication will experience significant improvement in latency, reliability, and efficiency. Moreover, the advancement in wireless communications will also impact multiple secondary or non-communication related users, such as smart grid, agriculture, pharmaceutical, biomedical, remote sensing, remote screening, and surveillance. All of these secondary users directly or indirectly will be using wireless communication. The extension to beyond wireless communication applications will call for significant enhancement in technology, infrastructure, proto- cols, network architecture, and regulations. All of which can lead to multiple novel or large-scale security, privacy, and even national security challenges.

Figure 1. Growth of communication services throughout wireless generations.

The THz spectrum, ranging from 95 GHz to 10 THz, can enable multiple benefits and applications for wireless communications, passive, spectroscopy, and imaging system. Although there are multiple technical and economic challenges associated with THz deployment, the rarely discussed challenge of security and privacy-related risks needs attention from researchers, manufacturers, and even policymakers [2]. THz spectrum could represent either a boon or a bane (or both) for security, privacy, and even national security. These include concerns over an array of increased risks, such as failure of devices, failure of the system, unauthorized or covert access, compromise of data, data integrity, impact on other services (apps), impact on critical infrastructure, securing dense deployment, and exposure of sensitive information. In this blog, we describe how the use of the THz spectrum could both introduce and negate security and privacy risks. We then present a set of technical and policy measures to mitigate such risks. We note that standards bodies and possibly government interventions will have a role in mitigating security, privacy and even national security risks.

The THz spectrum’s low coverage area and low penetration power make it inherently more secure. The THz spectrum has multiple characteristics making wire- less communication much more secure and resilient against attacks, e.g., jamming and eavesdropping, through spread spectrum coupled with low transmit power, beamforming with pencil beams, need for Line-of-Sight (LOS) and small user coverage, and frequency hopping over a huge frequency range. Despite these methods, links can be compromised to attacks through blockages, reflections through surfaces, and small-scale mobility of devices [3, 4]. Very few approaches have been proposed to mitigate these risks, either costly, complicated, or demanding too much user data. Even for a short distance with a reliable THz link, the system will require granular information about the user’s location and device orientation, mobility pattern, traffic pattern, surrounding environment, and blockages. This information might be too sensitive for a user to share across the wireless system, leading to multiple privacy risks and reducing users’ trust on THz technology. Significantly decreasing the size of antennas, densification, heterogeneity, and ubiquity of these THz devices makes the problem much more critical. The system has to manage many devices with varying security levels and a tremendous amount of sensitive information. A malicious actor will only need to hack into one such small device to access a backdoor into the whole system. Besides, THz devices are already being developed and tested for non-communication applications, such as remotely detecting hidden objects on a person, packaging material, and envelopes. Law enforcement can use these devices for surveillance at public events, which raises multiple privacy concerns. This tradeoff between invasive surveillance and mitigating imminent treat can potentially impacting national security. A summary of the benefits and challenges associated with THz’s security and privacy is shown in Table 1.

Table 1. List of THz properties that impact the security and privacy landscape for wireless communication and beyond applications. The symbols + and — signifies the benefits and challenges respectively.

The security and privacy challenges, shown in Table 1, can roll up to much bigger national security concerns if not managed now. These risks are rarely discussed and needs urgent attention from researchers, manufacturers, and even policymakers. Such THz characteristics, could represent either a boon or a bane (or both) for security, privacy, and even national security-related issues in B5G and 6G communication.

THz Characteristics- a Boon

1. Security Screening and Surveillance Systems: Using THz Spectrum to secure the society and extending the use to healthcare, climatology, law enforcement, and military sectors.

Fig. 2 The THz spectrum’s absorption coefficient for water vapor, overlayed with some specific frequencies and frequency ranges critical for detecting items, such as food, micro- organism, biomedical, pollution, weapons, and drugs-of-abuse. For proper functioning of spectroscopy services, the application might require a range of frequency-windows. Although we are interested in the absorption coefficient of water for wireless communi- cation, if the THz active devices are spatially close to spectroscopy services, the THz devices may have to employ some form of co-existence strategies.

2. Anti-Jamming: Using THz spectrum for lightweight anti-jamming measures while maintaining ultra-high throughput. The THz spectrum has large bandwidths, allowing devices to frequency hop over an extensive frequency range, a limitation inherent in the lower RF bands. A large number of hopping sub-channels reduces the probability of an adversary detecting the hopping sequence, and at the same time preserves the high throughput requirement of the system. The adversary operating in the higher frequency bands will have to generate high power throughout the vast bandwidth to overwhelm the receiver and also has to be a few meters away from the receiver, which is technically not feasible. Moreover, THz devices require narrow antenna beams, which is an added advantage for anti-jamming. First, the narrow antenna beams reduce the possibility of main-lobe jamming. Second, the beams need to be perfectly aligned, and the adversary will need to track the beam to jam a particular signal. Antenna beamforming gives THz spectrum an extra dimension (spatially) with numerous possibilities for transmitting the signal, making it nearly impossible for the adversary to jam a signal

3. Eavesdropping and Covert Communication: Using THz spectrum for lightweight covert communications while maintaining ultra-high throughput. The THz spectrum’s short coverage range, high antenna directivity, and sensitivity to atmospheric turbulence make it inherently immune to eavesdrop- ping, as shown in Figure 3.

Fig. 3 Secure communication between a transmitter (Alice) and receiver (Bob) in the presence of an attacker (Eve) can be achieved using THz’s (a) high antenna directivity and confining the beam spatially, and (b) atmospheric turbulence to make it difficult for distant Eve to sniff signals.

THz Characteristics- a Bane

1. Environmental Uncertainties: The THz spectrum suffers from high absorption and penetration losses, making it dependent on the surrounding environment. Eavesdropping and anti- jamming attacks can still occur in special scenarios where the atmospheric conditions are poor and the link has non-THz penetrable objects. Monitoring the surrounding atmospheric conditions and the objects present in the TX-RX path is critical for ensuring reliable and secure THz communication.

Fig. 4 Secure communication between a transmitter (Alice) and receiver (Bob) is disrupted in the presence of (a) an attacker (Malory) and (b) the presence of a blockage; thus, jamming the signal. In scenario (a), the signal is jammed by electronic means by targeting a jamming beam at the receiver at a particular operating frequency of f2. In scenario (b), the signal is jammed by physical means by placing a blockage between Alice and Bob. The attenuation rate through an object is dependent on the frequency resilience; hence signal operating on f2 is jammed, but not f1.

Fig. 5 Secure communication between a transmitter (Alice) and receiver (Bob) is disrupted the presence of an attacker (Eve). In scenario (a), the signal reaches Eve through reflection on an object. In scenario (b), the signal reaches Eve through scattering of the signal on atmospheric particles, water, rain and snow. In both scenarios, the attack’s success is dependent on the resilience of the THz frequency band. Let us assume, frequency type f1 is more resilient than frequency type f2. Thus, signal operating on f1 which be less susceptible to reflection and scattering.

2. Densification and System Failure: Mitigating vulnerabilities brought around by densification and ubiquity of THz devices while using lightweight security measures. Advancements of technology in manufacturing nano-meter sized antennas will become inexpensive. This will help in the scalability of THz devices for various applications, such as IoNT, BANNET, covert communication, remote surveillance, and ubiquitous applications. Due to the low coverage area of the THz, densification at this scale is required for reliable communication. A blanket of THz antenna can be placed in a room for relaying communication across long distances. These dense networks will generate significant amounts of sensitive information, which need to be filtered, anonymized, and managed for privacy risks.

3. Privacy Risks: Enforcing privacy measures to balance risks and system performance in the THz. Even for a short distance reliable THz link, the system will require perfect beam alignment. To do so, granular information about the user’s location, device orientation, mobility pattern, traffic pattern, surrounding environment, and blockages may be required. The user might not want this information to be shared through the wireless system.

4. Spectrum Access & Management: Preventing harmful interference and unauthorized access to the THz spectrum by a wide variety of dense, ubiquitous, and heterogeneous systems.

THz Characteristics- a Balancing Act

So far we have discussed the THz characteristics that are beneficial (BOON) and challenging (BANE) for security and privacy risks. To mitigate the challenges (shown in Table 1), in this section, we discuss the technical and regulatory solutions required to balance the technical performance and risks of the THz spectrum.

<For detailed information refer the Paper: Link>

1. Regulation & Standardization: Proposing an adaptive policy framework for accessing the THz spectrum by a wide variety of passive, spectroscopy, and communication systems.

2. Physical Layer Strategies: Using physical layer security and environmental parameters to mitigate attacks by adver- saries.

3. Link Layer Strategies: Improving link layer protocols to be more adaptive and aware of the surrounding environment to mitigate attacks by adversaries.

4. Network Layer Strategies: Using lightweight and efficient routing protocols to mitigate attacks by adversaries.

5. Privacy: Understanding the tradeoff between users’ privacy and system performance, and then enforcing stricter data collection, distribution, and retention mechanisms for a dense THz system.

6. National Security: The need for US’s global leadership in standardizing the THz spectrum use and securing US’s supply chain from vulnerabilities arising from poor, faulty, or malicious hardware and software manufactured by foreign manufacturers.

Summary

THz has a wide range of applications, from making wireless communications faster and interference friendly to supporting a broad set of scientific applications, such as passive systems, spectroscopy, and imaging. Moreover, THz properties are unique compared to other bands in the electromagnetic spectrum, making it more secure. If deployed strategically and opportunistically, THz can provide high bandwidth for wireless systems while maintaining security and privacy needs. THz does bring with it vulnerabilities and risks, which present national security concern challenges. In this paper, we catalog how the THz spectrum could introduce or negate such risks, as listed in Table 1. We then present a set of technical and policy measures, which can be used to ameliorate such risks, as listed in Table 2 <Refer the Paper: Link>. We note that where technical solutions fail to mitigate these risks, it may be necessary to consider how policy and/or standards can be applied to balance technical performance versus mitigating risks.

Papers:

1. ITU,“Minimum requirements related to technical performance for IMT- 2020 radio interface(s),” 2017. [Online]. Available: https://www.itu.int/md/R15-SG05-C-0040/en
2. R. Singh, W. Lehr, D. Sicker, K. M. S. Huq, “Beyond 5G: The Role of THz Spectrum” TPRC 47: The 47th Research Conference on Communication, Information and Internet Policy 2019. [Online]. Available: (link)
3. R. Singh, D. Sicker, K. M. S. Huq, “MOTH- Mobility-induced Outages in THz: A Beyond 5G (B5G) application,” in Proc. of IEEE Consumer Communications & Networking Conference (CCNC), 2020. [Online]. Available: (link)
4. R. Singh, D. Sicker, “Parameter Modeling for Small-Scale Mobility in Indoor THz Communication,” in Proc. of GLOBECOM, 2019. [Online]. Available: (link)