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How Cutting-Edge Microcontrollers Build Security From the Ground Up

Embedded processors are on the rise, getting smaller and smarter. But as more functions are embedded in smaller device footprints, security concerns are increasing. In this article, we will dive into the rising security threats and how new processor solutions are ensuring multiple layers of security for embedded systems. An excellent example of this are the latest products from Alif Semiconductor.

With increasing functionalities, power efficiency, and scalable performance, embedded processors are entering almost every market. You can find them in the automotive, industrial, medical, consumer electronics, and IoT sectors. Estimates show that the embedded processor market is set to grow from USD 21.8 billion in 2021 to USD 44 billion by 2030 at a CAGR of about 8.2%[1]. In other words, the number of embedded processors in the market is expected to double in almost nine years.

However, growth of this magnitude is accompanied by an increase in security threats. For instance, one in every five industrial control systems today faces critical security issues[2]. Embedded systems are often required to store, access, or communicate data of a sensitive nature, making security a serious concern. That is why security must become a priority for embedded systems at every stage of their lifecycle. Such security can provide mechanisms to protect an embedded system from malicious access and unauthorized usage.

Security vulnerabilities in embedded systems necessitate security measures

Security threats can emerge from both software and hardware vulnerabilities. Network-based attacks take advantage of such vulnerabilities to access and take over a device’s processor. The most common are buffer overflow attacks, code injection, and control-flow hijacking.

As we explained in our previous article, embedded security is a partnership between hardware and software. Since the software component is created by human engineers, it is inherently imperfect by nature. Holes in the written code can turn into exploitable bugs of which attackers and threat actors can take advantage. That’s where hardware security comes into play.

Hardware security helps fend off potential threats from happening at both the device and network level. This is characterized by multiple layers of security that enable inherent protection against malware attacks. By providing a root of trust (RoT), and encryption and decryption capabilities, hardware technologies like system-on-a-chip (SoC) can and should maintain the integrity and provenance of a device.

Here are five hardware security measures for embedded processors:

1. Root of trust (RoT)

s its name implies, a RoT is the trusted basis for all secure computing operations. This trust comes from its purposeful security that includes keys for secure boot and cryptographic functions. Implementing a RoT in hardware takes the shape of a stand-alone security module or a built-in security module in a processor, or SoC.

A hardware RoT is established during manufacturing, where a secret key is embedded in a device’s memory to assume the role of the RoT. Once certified by a public key infrastructure (PKI), this key can fundamentally help developers build secure and trusted communications between devices.

A RoT can be either fixed-function or programmable.

  • A fixed-function RoT is a finite state machine (FSM) that performs specific functions appropriate for IoT devices, including key management, data encryption, and certificate validation.
  • A programmable RoT is established around a CPU that can execute the functions of an FSM with further adaptability and functionality. It can face new attack vectors by running new cryptographic algorithms. It can provide layered security, isolated implementation, and anti-tamper capabilities.

2. Secure boot

Secure boot is a security standard that helps your device boot safely and protects it from any unauthorized software. It utilizes the public key signature provided by the trust anchor and ensures there is no tampering with the software by validating the boot image using the public key.

A public key signature is to digital communications what wax sealing is to historic official documents. It secures whatever information is inside. In this case, it helps establish the provenance of the primary software and its updates.

In case of time-sensitive boot requirements, accelerated boot code validation might be needed. That’s where symmetric keys come into play. A symmetric key can help speed up the verification process and approve the integrity of the software. However, it is a secret key known only to the device, as opposed to the public key.

3. Unique device identity

To establish meaningful communications, devices should have unique identities that are distinguishable and verifiable. Two main approaches to ensuring unique device identity are key injection and using a physical unclonable function (PUF).

  • Using key injection: This is where a key – or a cryptographically verifiable identity – is generated in a separate system and securely made accessible to the device. Key injection is a commonly used identification process.
  • Using a physical unclonable function (PUF): A PUF serves as a digital fingerprint of the device by showing a physically unique hardware characteristic that can help identify the device.

4. Trusted execution environment (TEE) or hardware security zone

A TEE is an isolated security zone enforced by the device hardware that allows for establishing a root of trust (RoT). This zone is built into the processor and enables security-sensitive processing to take place within the embedded system.

The most popular mode of security for TEEs is ARM TrustZone. It is a system-wide security approach that separates the device resources between the so-called “normal world” and the “secure world”. Security can be further enhanced beyond TrustZone through additional layers of security, as we will see in Alif Semiconductor’s embedded processors below.

Apart from that, a TEE can be run on an isolated CPU core that serves as a “security co-processor” to the main SoC. This isolation establishes a secure execution environment for sensitive processing.

5. Trusted platform module (TPM)

A TPM is hardware that is dedicated to ensuring the security of the device. It is a microcontroller that generates, stores, and uses internal cryptographic keys, encrypts sensitive information in the memory, and establishes the integrity of the system throughout the boot process. It also stores measurements that help with authentication and attestation to ensure trustworthiness.

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