Embedded Systems Academy

In a blog entry from last year, we announced a “Two-year project for security of CANopen and other small-packet networks.” It is now time to give you an update on where we are with our SPsec (Securing Small-Packet Networks) project.

It comes as no surprise that adding security to small-packet networks like CAN, I2C, LIN, Modbus, and other fieldbuses is a challenge. The small-packet sizes offer only limited space for security information like an authentication tag and often, these networks are handled by microcontrollers with limited computational and memory resources. We are now aiming at protecting all communication in such a network when our initial goal was to protect only selected communication channels. The reason here is that for many industrial applications, recent acts and regulations like the European Cyber Resilience Act (CRA) will require security-by-design in the near future. For several use cases, they will also request that all data at rest and in motion is both authenticated and encrypted.

We defined the following SPsec key points and cryptographic primitives:

• Minimal hardware requirements of participating MCUs
• Cryptographic functions used
• Point-to-point security for configurations or communications with an limited amount of communication channels
• Time-based rolling key derivation for automated refreshing of keys
• Group security for multicast network technologies like CAN

For more detailed information see our white paper “Cybersecurity Primitives for Small-Packet Networks“.

Our first proof-of-concept implementation will be based on the PCAN-Router FD from PEAK-System. These devices have two CAN (or CAN FD) interfaces from which we use one for unprotected communication from a host system. The router implements a SPsec sub layer and uses the second interface for the secure communication. This allows for easy test and debugging, as there will be one CAN bus with the protected and one with the unprotected communication allowing a direct comparison.

Later the SPsec sub layer will be added to our Micro CANopen source code and integrated into various CANopen or CANopen FD devices for further testing.

Stay informed by following this blog or our linkedin page for up-to-date developments.

The current status of the EU Cyber Resilience Act (CRA) is that manufacturers of devices with digital elements or any software have until 2027 to comply with the outlined rules and regulations. These include compliance issues like overall risk assessment, documentation and incident reporting – which have a huge organizational impact. Technology details mentioned in the CRA are limited, so there is some interpretation as to what it all means for embedded systems and fieldbus communication. When it comes to specifics, the annex talks about how to treat data in transit:

Text excerpts from Annex I, 1. (3) (c) and (d) (emphasis ours):

• Products shall protect the confidentiality of stored, transmitted or otherwise processed data, personal or other, such as by encrypting relevant data at rest or in transit by state of the art mechanisms.
• Products shall protect the integrity of stored, transmitted or otherwise processed data, personal or other, commands, programs and configuration against any manipulation or modification not authorised by the user, as well as report on corruptions.

In other words:

• When communicating or storing (to non-volatile memory) relevant data then encrypt it.
• When communicating or storing (to non-volatile memory) any data then authenticate it.

There is not much room for exceptions here, discussing what is relevant might be challenging. If it is not relevant, then why communicate or store it in the first place?

There might be some relief in Annex I, 1. (1) which says:

• Products shall be designed, developed and produced in such a way that they ensure an appropriate level of cybersecurity based on the risks.

This can be a way out for some applications if in the risk assessment a security expert can show that there is no risk in not protecting certain data. Nevertheless, the security assessment must also reflect the following two statements:

1. Apply security-by-design to the entire lifecycle (min 5 years), from development process to production, deployment, and use/maintenance.
2. Products integrated in or connected to a larger electronic information system can serve as an attack vector for malicious actors.

These two statements have a huge impact on all microcontroller communication like plain UART, RS-485, CAN or other fieldbuses. The second statement boils down to not making a difference between important and lesser important communication. Even the lesser important communication may serve as an attack vector to the system.

The first statement requires layered security mechanisms given that protecting a single aspect won’t be sufficient. Taking CAN as an example, let us have a look at the known three stages of most common attacks on CAN systems:

1. Get access to the CAN communication.
   For example by accessing the CAN wires or hijacking a device (or interface to another network) already connected.
2. Monitor the CAN communication to learn from it.
   The attacker learns which CAN frames are used for what.
3. Inject or replay CAN communication to maliciously trigger behaviour.
   The attacker “takes over” certain aspects of the system.

By protecting any one of these three stages, the attacker’s success can be thwarted, and the system might seem “secure”. However, what if in the foreseeable future an attacker finds a way around that single protection? Security-by-design requires that we pay attention to all possible stages of an attack and do not focus on a single point of potential failure.

In any future risk assessment of a system using any form of communication (fieldbus or application specific communications), manufacturers will need to show which steps they took to protect all aspects:

1. Which steps were taken to minimize physical access?
   How easy is it to access the network wires? Can diagnostic ports be protected? Which interfaces to other networks are there? How are they protected?
2. Which steps were taken to keep communication confidential?
   To prevent attackers from learning anything about the system, encrypt all relevant communication.
3. Which steps were taken to ensure communication integrity?
   To prevent attackers from manipulating frames, authenticate all relevant communication.

In summary, to be EU Cyber Resilience Act compliant, a lot of the future fieldbus communication needs to be both authenticated and encrypted. To simplify the risk assessment and documentation, this should be done for all communication. Otherwise, manufacturers need to be prepared to have a security expert document every unprotected communication as to why this specific data set is irrelevant enough so that even if read or manipulated it won’t possibly constitute a cybersecurity risk.

Follow this blog and/or our LinkedIn page to learn about latest related developments including our upcoming security solutions for CAN, CAN FD, CANopen and CANopen FD.

This year, Nuremberg’s doors open for the Embedded World (#ew24) from April 9th to April 11th. From EmSA, Peter, Chris and Olaf will be at the event all three days. If you want to talk to us about topics like CAN, CANopen, J1939 and CAN security, meet us at the booth of Peak-System, hall 1, booth 304.

As every year, the conference also features a CAN session. This year it is session “SESSION 2.2 CONNECTIVITY SOLUTIONS | CAN” (April 9th, starting at 1:45PM) with the following presentations:

Thilo Schuhmann: Standardized Cybersecurity in CAN-Based Systems

This paper concentrates on cybersecurity requirements specific to embedded systems employing Controller Area Network (CAN) communication, encompassing CAN, CAN FD, and the emerging CAN XL. Our primary focus lies on CAN XL, which incorporates CANsec, a data link layer add-on facilitating message authentication and encryption,in the data plane. In the control plane the specification of the CANsec Key Agreement protocol (CKA) is defining for key exchange and agreement mechanisms to allow broadcast communication for the authenticated and encrypted messages.

Reiner Zitzmann: Improved Network Start-up for Dynamically Changing Embedded CAN Systems

Controller Area Network (CAN) networks often serves as the conduit for data exchange; on the very deeply embedded level. Devices, connected to these embedded networks may be dynamically added or removed, by the end user. Thus these devices need to show a certain degree of plug and play behavior. Host controllers must have the ability to rapidly identify these devices. Unlike current implementations, the enhanced Layer Setting Services (LSS) enable CAN/CANopen devices to convey their identity to the host controller or LSS manager. This eliminates the need for laborious searches to determine the presence and type of newly added devices. The presentation shows the functioning of the improved Layer Setting Services, and practical use cases.

Olaf Pfeiffer: Collaborative Design of Security Measures for CAN and CANopen Systems

The rise of connected devices in the embedded world has intensified the need for strong security measures, especially in Controller Area Network (CAN) and CANopen systems. These technologies are crucial in a wide range of applications such as industrial automation, automotive systems, and medical equipment. Given the limited resources available in CAN protocols, security often becomes a challenging aspect to address effectively. This paper presents a joint project between Hochschule Offenburg and Embedded Systems Academy, focusing on overcoming these security challenges.
We argue that collaboration among multiple partners is essential for the design and implementation of effective, robust security measures. Our proposed security framework brings together expertise from various stakeholders to identify vulnerabilities, assess potential threats, and formulate countermeasures. A significant aspect of our project is the aim to standardize these security measures through the CAN in Automation (CiA) organization. This makes the security framework transparent and open for public review.
The framework is optimized for CANopen but can also be used by CAN, CAN FD, CANopen FD and other higher-layer protocols.
This paper will outline the architecture of our security framework, showing its applicability to a broader range of CAN or CANopen based applications.

You can’t make it to Nuremberg?

For the latest news and developments in CAN, CANopen and CAN Security, follow us here: https://www.linkedin.com/company/embedded-systems-academy/

For more info on these topics, also see our video collection at https://www.em-sa.com/video

Together with the Institute of Reliable Embedded Systems and Communication Electronics (ivESK, Prof. Sikora of Offenburg University), the Embedded Systems Academy has been awarded a research grant for a collaborative project focusing on embedded network security. The project is dedicated to developing a security framework for small-packet networks, with a specific emphasis on CAN and CANopen systems.

The initiative, internally referred to as “Inter-Layer Multi-Participant Security for Small-Packet Networks,” can be integrated within existing network layer protocols and offers multi-party security. It is adaptable to various small-packet network protocols used in embedded systems. Beyond CAN, CAN FD, CANopen and CANopen FD, it can also be used for I2C or RS-485 based systems. The project aims to combine established security mechanisms in a novel way and adapt them suitable for deeply embedded systems, devices and networks, where resources, such as memory, computing power, data rates and frame length are very much constraint.

The project’s goal is to ensure that the results are openly available and can be reused by the Special Interest Group “Safety/Security” within CiA (CAN in Automation).

We plan to regularly publish updates on our project’s progress. A first presentation is scheduled for the embedded world Conference in Nuremberg: On April 9th, 2024, we will present the paper “Collaborative Design of Security Measures for CAN and CANopen Systems” in the connectivity track, session 2.2 on CAN. If you are interested in contributing to the specification process or in beta-testing early implementations, please feel free to contact us (contact form on this web page or mail to info@esacademy.de).

This Project is supported by the Federal Ministry for Economic Affairs and Climate Action (BMWK) on the basis of a decision by the German Bundestag.

The 17^th international CAN Conference is an online event about the Controller Area Network happening from June 14^th to June 17^th, 2021. Papers presented cover topics such as updates on the physical and data link layer for CAN FD and XL, CANopen testing, CANopen FD and Security.

The tutors of EmSA participate in presenting two papers: “A simplified classic CANopen to CANopen FD migration path using smart bridges” and “Achieving multi-level CAN (FD) security by complementing available technologies”.

The paper about smart bridges introduces a solution to easily combine classical CANopen devices with CANopen FD devices. The bridges developed here offer one classical CANopen and one CANopen FD port and “auto-translate” CANopen and CANopen FD messages transparently. As an example, SDO transfers on the classical CANopen side are automatically translated to USDO transfers on the CANopen FD side.

The paper about security reviews currently available security solutions for CAN (FD) and examines how they complement each other. The security methods combine here are CAN message ID guarding, a CAN crypto layer and (D)TLS.

For the first time, the iCC combines papers with open CiA IG and SiG (Interest Group and Special interest Group) meetings. Here “open” means that after registration anyone can participate to see how the different work groups operate. Our engineers will participate in the SIG special car add-on devices (CiA 447) and the IG CANopen FD.

For more details and registration, see www.can-cia.org/icc

Over the last years we published more than 50 articles, papers, books, webinars and we also continuously updated our training materials. However, some of the training material and especially scientific papers only reach a small percentage of the embedded community. Therefore we decided to publish more free educational videos to reach more of you. As a start we created several playlists on our EmSA Youtube channel. These include:

• CANopen FD Intro:
  Introductory videos to CANopen FD, also covering some basics like an introduction to the CANopen Object Dictionary concept
• CAN (FD) Security:
  Video collection about CAN and CAN FD security challenges and solutions
• MCUXpresso Middleware:
  Video collection about NXP’s MCUXpresso and CANopen libraries included

We plan to publish more videos in the upcoming month, further focusing on CAN, CAN FD, CANopen, CANopen FD topics including introductory videos as well as in-depth technology classes.

Please subscribe to the channel to stay informed about new videos published.

This year we present multiple papers at the upcoming Embedded World (25th to 27th of February in Nuremberg, Germany) and the international CAN Conference (17th to 18th March in Baden-Baden, Germany). Chris and I will be talking with our partners of NXP Semiconductors, PEAK

-Systemtechnik and the Hochschule Offenburg about CAN (FD) security and CANopen (FD) Smart Bridging. In our security papers, we examine how different existing and CAN capable security methods can best complement each other. With SmartBridgingFD we show how classical CANopen devices or networks can easily and transparently be mixed with newer CANopen FD installations. As classical CANopen and CANopen FD are not compatible on the bitrate level, they can not share the same CAN wiring. However, the SmartBridgeFD allows combining classical CANopen and new CANopen FD networks into one large logical network.

At the Embedded World, you can see the SmartBridgeFD integrated into the CANopen FD demonstrator at the CiA booth (hall 1 booth 630). Another of our CANopen (FD) demos will be displayed at NXP Semiconductors (hall 4A booth 220), as our CANopen software is now part of NXP’s latest SDK. Our CAN hardware partner PEAK Systemtechnik is in hall 1 (booth 483).

The Embedded World conference program is now online, we are in Session 2.1. The program for the international CAN Conference is here, our papers are in Session IV and VII.

Our authors Christian Keydel and Olaf Pfeiffer published an article in the current CAN newsletter, summarizing the current status of CAN security specifications.

Please follow the link above for more details.

Excerpt:

End of June 2019, the CiA association hold a phone conference for safety and security issues. Holger Zeltwanger gave the participants an update regarding “base documents”. When defining security solutions for Classical CAN, CAN FD, or CAN XL systems, it would be preferable to not start from scratch defining security basics for embedded systems or embedded communication systems. Unfortunately, the current draft of ISO 21434 “Road Vehicles – Cybersecurity engineering” does not seem to be suitable, as it is very generic and not yet completed. It is more of a guideline what designers and developers need to keep in mind when designing a “secured” vehicle.

Another document suggested is the “Baseline Security Recommendations for IoT” by the European Union Agency for Cybersecurity. Until the next meeting, CiA will review and report, if that document is suitable to be referred to also by CiA documents. CAN XL is still in an early specification phase and the related special interest group, recognizing the possibility for security features in hardware to be part of future CAN XL controllers, therefore suggested adding security features to CAN XL first. One of the discussed options is a blacklist/whitelist scheme like the one implemented by the NXP secure CAN transceiver family. Such a scheme can eliminate several potential attack vectors at once if all participants in a CAN (XL) network actively support it. Once we see which security features made it into the CAN XL specification (and hardware), we can review if any of these can still be applied to CAN FD, too, for example on the transceiver level.

However, potential CAN controller specific hardware security features will most likely not be suitable to migrate back into CAN FD, so protocol based security solutions are still required.

Darmstadt and Hannover, June 12th, 2019. PEAK-System Technik GmbH (www.peak-system.com) and Embedded Systems Academy GmbH (www.esacademy.de) have deepened their partnership to provide common CANopen, CANopen FD, and J1939 solutions. For more than 15 years, Embedded Systems Academy GmbH (EmSA) has offered numerous CANopen software products including monitors, analyzers, simulators, configurators, and protocol stacks for the CAN (Controller Area Network) hardware of PEAK-System Technik GmbH (PEAK). Building on that partnership, PEAK has now become a shareholder and partner of EmSA.

“By formally joining the PEAK Group of companies, we can now more easily share resources and are better positioned to streamline development processes that involve both CAN hardware and software,” says Olaf Pfeiffer, General Manager of Embedded Systems Academy GmbH.
Current projects of PEAK and EmSA include CANopen (FD) generic input and output devices, CANopen (FD) protocol libraries, security options for CAN and diagnostics and test systems for CANopen (FD) and J1939.

“The deepened partnership with EmSA will provide our hardware customers with a variety of easy-to-use software products for CANopen, CANopen FD, and J1939 applications,” says Uwe Wilhelm, General Manager of PEAK-System Technik GmbH. “We’ll announce our new joint CANopen and CANopen FD solutions on our websites and blogs over the coming months.”

Our tutors Christian Keydel and Olaf Pfeiffer published their next security article in the CAN newsletter. This one is about “making security work” for already deployed CAN systems with limited MCU resources available.

Excerpt:

Some things appear to have not changed significantly in the past 20 years of Embedded Systems programming. Back then we would start developing minimal solutions for clients that wanted to add CANopen using “as few resources as possible”. Today, clients want to add CAN security to an already deployed system and again, often with only minimal resources available. Same situation, different technology.

The biggest change compared to unsecured CAN communications is the added security information, and the question is where in the CAN frames we want to put it. In networks that only use 11-bit-identifier CAN frames, like virtually all CANopen systems do, it is convenient if secure frames use a 29-bit CAN identifier instead, as illustrated in figure 1 “Adding security information to a CAN frame”. In the available extra 18-bits long “security record” we can then put a 10-bit signature and some control information. This method greatly simplifies mixing non-secure and secure CAN communications – a secure frame then still uses the same lower 11-bit portion of the 29-bit CAN identifier as the unsecured frame would, and the added security record can be easily recognized. The 18-bit record comprises a 2-bit truncated key refresh counter, a 6-bit truncated timer value and the 10-bit Micro CANcrypt signature. As all devices synchronize their refresh counter and timer locally, the truncated information is enough for receivers to internally maintain the full counter and timer values.

In comparison to CANrypt, Micro CANcrypt uses a simplified key synchronization method. Figure 2 “The Secure Key Sync cycle” illustrates how four event messages use the extended security record to share information. Here the extended security record contains a 16-bit timer and a 16-bit random value. These synchronised messages are used once per second to share / create an initialization vector (IV) for a dynamic, current key from the session key and to synchronize a 16-bit timer value and an 8-bit key refresh counter. A block cipher is used to generate the dynamic key from a shared symmetric permanent key using the IV generated in each cycle.

For more details, read the original article in the CAN Newsletter June 2019