edfas.org ELECTRONIC DEV ICE FA I LURE ANALYSIS | VOLUME 24 NO . 4 22 SECURITY ASSESSMENT OF NONVOLATILE MEMORY AGAINST PHYSICAL PROBING Liton Kumar Biswas, M. Shafkat M. Khan, Leonidas Lavdas, and Navid Asadizanjani Florida Institute for Cybersecurity Research (FICS), University of Florida, Gainesville litonkumarbiswas@ufl.edu EDFAAO (2022) 4:22-32 1537-0755/$19.00 ©ASM International® INTRODUCTION Nonvolatile memory (NVM) devices are an indispensable part ofmodern computing systems. The drive toward portable, lighter, and compact systems is making NVMs even more essential, as data storage requirements continue to grow. NVM is often required for a system to store a range of different data types, like boot code, firmware for embedded systems, user applications, media files, keys, and passwords. This also includes confidential data that needs to be retained, even when the integrated circuit (IC) is powered off. Examples include private keys for cryptographic operations, authentication data, and configuration code. Previously, read-only-memory (ROM) was the most common form of NVM, despite only being able to have its contents written once, during fabrication. More recent technologies, such as erasable programmable read-only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM), allow the ability to erase and reprogram the contents. However, a majority of the market share currently belongs to flash memory. From 2019 to 2025, the NAND flash market size is expected to nearly double in size.[1] Manufacturers like Samsung and Micron are setting record-breaking investmentmilestones in response to toweringdemands for NVMs acrossmultiple industrial sectors. Contemporary research focuses on developing more efficient NVM devices and can be categorized by two main research directions. One path prioritizes the use of inorganic materials to yield products like ferroelectric RAM (FeRAM), magnetoresistive random access memory (MRAM), and phase change materials (PCM). The other path considers the use of organic materials made of polymers with ferroelectric or conductance switching properties. Regardless of the particular researchdirection, the complexity usually increases every time a new device surfaces. The main working principle remains the same for NVM, which is to permanently store “high” and “low” digital states. Also, modern designers broadly consider parameters like cell size, read-write times, endurance, and compatibility with CMOS technology. However, the differences among specific implementations lie in which physical or chemical phenomenon is exploited to obtain a pair of complementary electrical states. For example, PCMs depend on the physical state of an alloy, with one phase corresponding to low resistance and the other corresponding to high resistance. Meanwhile, spin transfer torque RAM (STT-RAM) leverages the difference in orientation of two ferromagnetic layers to distinguish between a high and a low state. Unfortunately, the variousphysical implementations of NVMcannot always be considered secure froma hardware security perspective. The physical phenomena in these emerging devices canbe observedor interferedwithusing different imaging or fault injection techniques. There are many emerging physical probing modalities that can be used maliciously to gain unauthorized access or violate the integrity of stored information in a NVM device. Thus, ensuring the confidentiality and integrity of stored data becomes a subject of conspicuous concern. This work presents a detailed and methodical discussion about how existing and emerging memory devices can fall prey to attacks through various physical modalities. These physical attacks[2] are a well-defined class of hardware attacks, constituting both reverse engineering and fault injection threats. With the increase in complexity of emerging NVMdevices, and the simultaneous advancement of modern imaging and failure analysis equipment, the security of data stored inNVMs needs to be considered an important design parameter. This article will:
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