  Citation: Rahimi, P.; Singh, A.K.; Wang, X. Selective Noise Based Power-Efficient and Effective Counter-Measure against Thermal Covert Channel Attacks in Multi- Core Systems. J. Low Power Electron. Appl. 2022, 12, 25. https://doi.org/ 10.3390/jlpea12020025 Academic Editor: Andrea Acquaviva Received: 6 January 2022 Accepted: 7 March 2022 Published: 3 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Journal of Low Power Electronics and Applications Article Selective Noise Based Power-Efficient and Effective Countermeasure against Thermal Covert Channel Attacks in Multi-Core Systems Parisa Rahimi 1, * , Amit Kumar Singh 1 and Xiaohang Wang 2 1 School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK; a.k.singh@essex.ac.uk 2 School of Software Engineering, South China University of Technology, Guangzhou 511436, China; xiaohangwang@scut.edu.cn * Correspondence: pr19863@essex.ac.uk Abstract: With increasing interest in multi-core systems, such as any communication systems, infra- structures can become targets for information leakages via covert channel communication. Covert channel attacks lead to leaking secret information and data. To design countermeasures against these threats, we need to have good knowledge about classes of covert channel attacks along with their properties. Temperature–based covert communication channel, known as Thermal Covert Channel (TCC), can pose a threat to the security of critical information and data. In this paper, we present a novel scheme against such TCC attacks. The scheme adds selective noise to the thermal signal so that any possible TCC attack can be wiped out. The noise addition only happens at instances when there are chances of correct information exchange to increase the bit error rate (BER) and keep the power consumption low. Our experiments have illustrated that the BER of a TCC attack can increase to 94% while having similar power consumption as that of state-of-the-art. Keywords: selective noise; multi-core systems; thermal covert channel; countermeasure; attack detection 1. Introduction Covert channels are communication channels used to transmit information. In chip- level security, covert channels are types of attacks that can create the capability of trans- ferring data and information between processes that are not allowed to communicate by the system security policy. Two parties with the aim to exchange covert information can easily communicate and transfer information over a shared network without being detected. Therefore, it is hard to identify covert channels, which hence can contribute to very serious damage to security approaches if they are used for malicious purposes. In many communication media, the covert channel information is seen, such as timing, heat, or indistinct sounds. There is a wide range of side channels that may exist in a multi-core system, however, a covert channel, which uses heat as a way to transmit information and data, can be particularly dangerous. The heat transfers are known as thermal covert channels (TCC) [1]. Thermal covert channels can be traced in multi-core systems. As in any communication system, a thermal covert channel includes a pair consisting of a transmitter and a receiver [2]. On the transmitter side, the temperature signals are generated from sensitive data such as user passwords by manipulating other activities like power consumption. The receiver’s side, which is on the other end of the data transmission, reads its thermal sensor and recovers the original sensitive information or data transmitted [3]. Figure 1 illustrates an eight-core chip example, which assumes that there is a covert channel between core A and core B. It should be noted that core A is placed in a secured zone, where sensitive information does not have permission to be shared with the other cores outside this zone, and core B is J. Low Power Electron. Appl. 2022, 12, 25. https://doi.org/10.3390/jlpea12020025 https://www.mdpi.com/journal/jlpea