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Six security tips for embedded systems

  Knowledge

Man-in-the-middle attacks, hacker attacks, spying and tampering, memory data errors – embedded systems are exposed to various threats. Bernd Hantsche, Head of the GDPR Team of Excellence and Marketing Director Embedded & Wireless at Rutronik, offers six tips to enhance security when transmitting, saving, and processing data in embedded systems.

Secure data transmission

Choice of the wireless standard is a key factor for embedded system security as each one is exposed to different potential attack scenarios:

ZigBee and Thread, featuring a channel bandwidth of 5MHz at each of the 16 channels, are particularly resistant to smaller signal interferences.

WiFi is even more robust thanks to a bandwidth of 20MHz per channel. However, WiFi is popular with hackers because it is used to send very large amounts of personal data. In contrast, the WPA2 protocol does not offer adequate protection.

  • Tip 1: In addition to WPA2 with a strong WPA2 key, also use SSL / TLS protocols and deactivate WPS (WiFi Protection Setup). Since the WPA2 key is replaced with a 4-digit PIN for WPS, it is fairly easy to crack. Greater security is offered by a MAC filter, which only gives listed devices access to the network.

With Bluetooth it is possible to distinguish between three variants:

Bluetooth EDR (Enhanced Data Rate) utilizes Adaptive Frequency Hopping (AFH) to prevent frequencies blocked by WiFi and Forward Error Correction (FEC) to detect and correct errors during data transmission. Bluetooth EDR is considered secure due to 128bit AES (Advanced Encryption Standard).

Bluetooth Low Energy (BLE) utilizes further security measures in addition to AFH and FEC, e.g. device authentication and message encryption.

Bluetooth 5 has the same security features as BLE but additionally offers four times the range or eight times the data transfer rate. The risk in this case: Hackers can attack data across much greater distances.

  • Tip 2: Select a Bluetooth 5 chip or module with integrated encryption, e.g. SoC nRF52840 from Nordic Semiconductor. By employing on-chip ARM Cryptocell, a cryptographic co-processor, it provides industry-compatible security standards for embedded systems.

NFC and RFID are ideal for sensitive areas: It is practically impossible to capture data due to their limited range of just a few centimeters. RFID and NFC chips and modules with security features are available, e.g., from STMicroelectronics, Toshiba, Melexis, Murata, Fujitsu, and Panasonic. For instance, M24LR04E-R from ST uses passwords to protect individual memory sections with freely configurable read and write access.

Reliable data memory

A study carried out by CERN showed: On average, there are undetected bit errors in every 1016 bits, usually due to cosmic rays. In embedded systems, this can result in far-reaching corruption and thus unreadable or completely destroyed data, erroneous actions or even cost-intensive downtime.

  • Tip 3: Save data in a RAID system (Redundant Array of Independent Disks). Since a RAID system combines multiple hard drives, usually HDDs or SSDs, to create a logical drive, the probability of failure drops to approx. 0.0001% - in contrast to approx. 2.9% for a conventional data storage system.
  • Tip 4: An ECC (Error Correction Code) RAM is recommendable for applications that frequently read and write the memory. This type of RAM module detects and corrects smaller data errors by generating a redundant control bit for every saved byte.

To additionally protect embedded systems against hacker attacks and industrial espionage, a memory should be equipped with encryption and authentication technologies. In this case, you have a choice between hardware and software solutions. Software solutions are adequate if attackers are unable to get through to the hardware - but there is always the risk of the brute-force method being used.

  • Tip 5: Encryption and authentication in hardware offers a much higher level of security: Hardware authentication with a retry counter or two-factor identification also protects against brute-force attacks. Encrypting and decrypting data via hardware solutions is also secure since the key is not saved on the same platform, as is the case with software solutions. A security memory with encryption and further security features is available, e.g., from Swissbit, Apacer, Seagate, and Transcend.

Data processing protection

Microcontrollers play a key role in networked embedded systems - as part of the IoT, Industry 4.0, and robotics, they act as a shield against tampering and cyber attacks. To achieve these goals, microcontroller manufacturers utilize development processes certified to various security standards, thus offering customers a secure end-to-end solution through a verified manufacturing chain.

In the meantime, standard microcontrollers are also available with numerous hardware-based security features, e.g.:

- Advanced Encryption Standard (AES) with 128 or 256bit key

- Cyclic Redundancy Checks (CRC) ensure data integrity when transferring or saving data

- Error Correction Codes (ECC) in the memory detect and correct errors when saving and transferring data, thus offering protection against "bit dumping"

- Clock Security Systems (CSS) enable clock recovery through independent clock sources

- Anti-Tamper Mechanisms protect against physical hardware attacks outside the microcontroller

- Real Time Clocks (RTC) add a timestamp to each tamper detection event

- RTC register protection blocks unauthorized write operations

- Debug Locks prevent unauthorized access through the debug interface

- Memory Protection Units (MPU) split the memory into sections with varying access rights

Many of the hardware security functions can be further extended with software measures.

  • Tip 6: If a microcontroller is used in the embedded system without or with insufficient security functions, we recommend the application of a Security IC. Since, despite having a cryptographic protocol, the key can be read from an unprotected microcontroller through simple physical attacks. It seems this is quite a common practice, especially if websites such as "ic-cracker.com" and "break-ic.com" are anything to go by. Security ICs protect an embedded system against unauthorized accesses and physical attacks, while enabling secure boot processes and firmware updates. Another benefit: A security IC additionally enhances microcontroller performance by assuming its encrypting and decrypting activities. Security ICs are offered, e.g., by Infineon through its Optiga™ Trust series. It features integrated ECC 521 and RSA 2048 crypto systems on a Java-based OS. Equally high security standards are guaranteed by the STSAFE series from STMicroelectronics, e.g. through secure authentication, protected keys, and encrypted communication.

Find components at www.rutronik24.com.