COVER STORY ADVERTISEMENT FEATURE
accelerators for various crypto functions, and a shielding layer over sensitive parts of the chip. The choice of the functions implemented in any given system will be a give and take balance between the level of security required against the extra cost of the hardware.
AN EXAMPLE The recently released LPC55S6x MCU from NXP integrates many of the hardware security features described above, making it unique in the MCU market. It has dual Arm Cortex-M33 cores with one CPU supporting TrustZone-M, and several coprocessors. While the chipset provides a secure boot with anti-rollback protection, the hardware also supports real-time execution of encrypted images from flash memory. The flash content is only decrypted in the execution path of the core. Thus, malicious attempts at reading the flash memory directly would only expose encrypted data: the software IP and associated data is protected. The LPC55S6x MCU uses a PUF based on a dedicated block of SRAM. Because of variations in each transistor, when the SRAM is turned on, each memory cell comes up as either a one or a zero. This is consistent every time the SRAM powers up, so these start-up values create a random and repeatable pattern that is unique to each chip.
NXP’s LPC MCU family is a secure option for hardware designers
This silicon fingerprint is turned into a secret key that can be used to uniquely identify the device, providing a hardware root of trust for the other security functions. There are several hardware accelerators for real-time encryption/ decryption of data and acceleration of various symmetric and asymmetric cryptographic algorithms. It also has tamper detection, secure GPIO and DMA, and a secure debug system that requires authentication in order to be enabled. LPC55S6x combines all of these in a complete security package; it provides a high level of security for many IoT and embedded applications, at minimal cost. The second Arm core and the DSP coprocessor can be used for executing complex application software. For example, machine-learning and inference systems can be implemented using the Arm CMSIS-NN library. This is a collection of high-performance, memory-efficient neural-network kernels, optimised for the Cortex-M processor core. This can be used with industry-standard frameworks such as Caffe, to implement applications based on image classification, speech recognition and natural language processing for human interfaces. This is the same technology that enables applications such as a car that recognises
the driver and automatically adjusts the seats and driving
settings. Robots that can recognise objects and people in their environment can work more safely in
/ ELECTRONICS
close collaboration with human workers. For example, a vending machine could recognise customers and ask if they want their usual choice of hot drink. The signal processing capability could be used, along with facial recognition, to implement beam-forming, using multiple microphones to isolate voices in a noisy environment and identify the current speaker.
IN CONCLUSION The increasing need for security in IoT systems is being met by the addition of hardware to support security functions in modern microcontrollers. This simplifies embedded security with a hardware root of trust for secure authentication, communication and data storage: it needs to meet the cost constraints of embedded systems. The LPC55S6x MCU shows how higher levels of integration, made possible by using a high-density semiconductor process, can enable more security functions to be included in an MCU, without sacrificing either cost or performance. EBV Elektronik is a technical distributor with a good understanding of IoT requirements, due to expertise in relevant vertical markets, such as industrial and automotive, and technologies, such as security, wireless communication. EBV can provide comprehensive technical support at all stages of the design process.
EBV Elektronik
www.avnet.com/ebv
ELECTRONICS | DECEMBER/JANUARY 2020 9
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