• • • SMART BUILDINGS & IOT • • •


Technical approaches to defend and protect IoT nodes


W


ith this growth comes an equal growth of opportunities for attackers. The estimated annual cost of cyber-attacks


ranges from tens of billions of dollars to over a trillion, and it too keeps rising. Therefore, security considerations are now essential to continue the successful scaling of the IoT. IoT security begins with the security of the IoT nodes. No company wants to see its name in the same


sentence as “breached, and customer data was stolen.” What’s more, connected devices are also subject to government regulations, such as FDA rules for medical devices, US/EU cyber security requirements for Industry 4.0 critical infrastructures, and several new emerging standards for the automotive industry. Those requirements push for high-level security


while not explicitly mandating the use of hardware- based security. However, IoT nodes are often large- volume, cost-optimised appliances, creating challenges to balance security and cost.


Creating secure nodes


using a “Roof of Trust” How can we design a cost-efficient yet secure IoT node? Creating a secure IoT node begins with a “root of trust” (also known as “Secure Element”), a small affordable integrated circuit designed to offer security-related services to the node. Examples of these functions are data encryption


for preserving confidentiality and digital signatures to ensure authenticity and the integrity of information. The ultimate goal of the root of trust is to ensure that the secret keys used for data encryption or digital signatures are protected against disclosure.


The biggest challenge for “root of trust” security


ICs is resistance against physical attacks, such as direct probing and so-called side-channel attacks.


Physically unclonable


The “Root of Trust” concept ensures authenticity and integrity for security-related services


function (PUF) Unfortunately, because direct probing attempts to observe internals of microcircuits, memory technologies typically used in general-purpose microcontrollers (i.e., EEPROM or Flash) are not secure. An attacker can directly observe the memory contents at a relatively modest cost using Scanning Electron Microscopy (SEM). The semiconductor industry has developed the “physically unclonable function” (PUF) technology to mitigate this risk. The PUF is used to derive a unique key from the intrinsic physical properties of the chip. Those properties are far more difficult to probe directly, making it impractical to extract the resulting key via direct probing. In some instances, the PUF-derived key encrypts the rest of the internal memory of the root of trust and, therefore, protects all other keys and credentials stored on the device.


22 ELECTRICAL ENGINEERING • DECEMBER 2022/JANUARY 2023


Stephane di Vito


Robert Muchsel


Don Loomis


Ten billion IoT nodes are connected today, ten times more than just a decade ago, and the trend is continuing unabated, says Analog Devices’s Stephane di Vito, senior principal MTS, Micros, Security & Software; Robert Muchsel, Fellow, Micros, Security & Software; and Don Loomis, vice president, Micros, Security & Software


PUF technology mitigates the risk from direct probing of microcircuits


Side-channel attacks are even cheaper and less


intrusive. They leverage the fact that electronic circuits tend to leak a signature of the data they are manipulating, for example, over the power supply, radio, or thermal emissions. The subtle correlation between measured


signals and the processed data can lead to successfully guessing the value of a secret key after a moderately complex statistical analysis


electricalengineeringmagazine.co.uk


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