Electromagnetic (EM) information leakage encourages attacks, wherein the attackers passively capture and analyze EM waves that are unintentionally generated by devices. Generally, devices with weak EM emission intensities are not targeted. However, even these devices would be subject to attacks if it becomes possible to actively sense the electrical changes that occur within them when information is processed. This article demonstrates the feasibility of the information leakage threat induced by the active sensing of input impedance changes in the input/output (I/O) circuit of an integrated circuit (IC). Specifically, the changes in the input impedance when information was transmitted from the IC, were measured by irradiating the EM waves from outside the target device. This article labels the threat as Echo TEMPEST. The experiment validated Echo TEMPEST with an evaluation board that simulated the I/O circuit of the IC, UART modules, and USB keyboards. It was also demonstrated that attackers could control the distance (obtained information from the target device), depending on the intensity of the irradiated EM waves. Furthermore, we discussed countermeasure methods focusing on the conditions for executing Echo TEMPEST.

True random number generators (TRNGs) based on ring oscillators (ROs) are employed in many devices because they can be constructed with a simple circuit structure. Many systems are affected if an RO-based TRNG is attacked, and its security is degraded. Conventional attacks against RO-based TRNGs reduce randomness using direct physical access to the target device and/or modification/invasion of the device or the equipment on which it is implemented. However, depending on the physical location of the device and its tamper resistance measures, directly accessing the device or operating/modifying the implementation may not be easy. This study introduces a noninvasive attack against RO-based TRNGs. In this attack, we intentionally induce sinusoidal electromagnetic waves in a TRNG and estimate the change in its randomness under this interference by observing the signal leaked from the TRNG from a distance. We also consider countermeasures against noninvasive attacks on TRNGs.

Threats that cause malicious function such as information leakage and denial of service by adding hardware trojan (HT) to a device constructed using inexpensive elements at component level after shipment have been reported. The detection method after shipment, which is different from HT detection inside IC is required because of the easiness adding component-level HT to products. The testing method to detect modification on board will achieve the detection of component-level HT. In this brief, we focus on the HT implemented in the wiring connected to integrated circuits. Since the component connection constantly affects the impedance of the wiring, we propose a detection method for such HT implemented outside the IC by measuring the change in the impedance of the wiring. For the detection of malicious modification after shipment it is necessary to excite a pulse signal from the IC that achieves high security, such as a secure microcomputer, and observe the signal reflected inside the secure IC by the discontinuous portion of the impedance on the board. If the reflected signal is different from the shipping test, it can be judged that HT is mounted. We adopted time domain reflectometry (TDR) to realize the above method, and we demonstrate experimental result of component-level HT detection using TDR with measuring instrument and TDR from secure IC. As a result, a significant change in the amplitude due to the impedance change was obtained from the reflected wave measured inside the IC with and without the MOSFET used as the HT using this method.

Electromagnetic (EM) remote visualization of screen images attacks (RVSIAs) is among the most actively researched topics in hardware security. Target displays are being developed daily; for example, recently developed high-resolution displays have multiple divided areas on the screen, and each area transmits different pixel information. In this case, it is difficult to reconstruct the screen using the conventional methods because the target screen information is leaked by multiple lines at the same frequency and timing, and multiple screen information is mixed into the EM waves. By contrast, in this article, we propose a novel RVSIA method that focuses on the difference in the transfer functions of multiple emanations from a high-resolution display. Considering the structure and signal transmission method of recent high-resolution displays, the proposed attack method observes leaked EM waves from multiple observation positions and alters the receiving frequencies of the receiver. For the first time, we have been able to separate multiple screen information contained in leaked EM waves using an independent component analysis method. In the experiments, we applied the proposed method to an actual laptop PC that divides the screen into multiple areas. As a result, it was possible to reconstruct screen information using the proposed attack method. Thus, the proposed method enables successful attacks against recent high-resolution displays. Furthermore, the measurement equipment employed remains similar to those utilized in the conventional attacks.

A supply-current equalizer disables a Correlation Power Analysis (CPA) attack on an AES cryptographic processor. An intermittent equalizer operation only at processing rounds critical to key disclosure suppresses the equalizer power overhead significantly. For this low-power intermittent operation, a Thru operation mode is proposed with minimum hardware overhead. A level-shift comparator hides its own power consumption in an internal equalized virtual supply to guarantee secure protection of a secret key. Test-chip measurement in 0.18μm CMOS successfully demonstrates CPA-attack resiliency. For the key protection against mostly-common last-round CPA, the equalizer power overhead is reduced by 11x which is only 8% of 128bit AES processor power consumption, and by 4x even including the initial/1st-rounds CPA protection capability.

Intentional electromagnetic interference (IEMI) of information and communication devices is based on high-power electromagnetic environments far exceeding the device immunity to electromagnetic interference. IEMI dramatically alters the electromagnetic environment throughout the device by interfering with the electromagnetic waves inside the device and destroying low-tolerance integrated circuits (ICs) and other elements, thereby reducing the availability of the device. In contrast, in this study, by using a hardware Trojan (HT) that is quickly mountable by physically accessing the devices, to locally weaken the immunity of devices, and then irradiating electromagnetic waves of a specific frequency, only the attack targets are intentionally altered electromagnetically. Therefore, we propose a method that uses these electromagnetic changes to rewrite or generate data and commands handled within devices. Specifically, targeting serial communication systems used inside and outside the devices, the installation of an HT on the communication channel weakens local immunity. This shows that it is possible to generate an electrical signal representing arbitrary data on the communication channel by applying electromagnetic waves of sufficiently small output compared with the conventional IEMI and letting the IC process the data. In addition, we explore methods for countering such attacks.