Embedded Systems Academy

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

The CANgineBerry (www.cangineberry.com) is a smart coprocessor module for the Raspberry Pi®, other popular embedded microprocessor systems or a PC. It allows offloading CANopen tasks from the main system while communicating with it though a regular serial port which greatly simplifies application development. Firmware for different purposes can be programmed through the same interface. New releases for the CANopen Device and Manager application firmware are now further enhancing the functionality of the CANgineBerry.

The CANopenIA-BEDS (V1.5) firmware for CANopen devices now also supports the tunneling of plain-CAN messages for special cases where CANopen is not used or the network needs custom messages. It also adds CANcrypt to support secure and authenticated CANopen communication between up to 15 participants. Lastly, it now supports an advanced manual triggering for Transmit Process Data Objects (TPDOs) where the host application can decide when exactly to trigger the transmission of a TPDO in addition to the standard fully-automatic mode, .

The CANopenIA-MGR (V1.7) firmware implements a self-configuring CANopen controller/manager. It contiuously monitors the network for new CANopen nodes and scans their configuration in order to set up automatic PDO handling. Also here, the new version implements advanced manual triggering options for TPDOs. For example, when the application wants to write data to a remote CANopen node’s Object Dictionary (OD) entry, the default behavior is that the controller automatically decides which transport — PDO or Service Data Object (SDO) — to use, depending on whether that OD entry is part of a PDO or not. In some cases, more control is desirable, though, so now the application can disable the automatic handling and manually select SDO vs. PDO as well as manually trigger TPDO transmissions.

The latest CANgineBerry software and firmware is available here: [CANgineBerry.com]

The CANgineBerry is available here: [US] [UK] [EU] [DE]

With every start of a new year, those preparing for the Embedded World and its conference in Nuremburg get busy – so do we. This year our tutors and partners present several papers, mostly around CAN (FD), CANopen (FD) and security issues. Over the last year it became clear that in embedded communication there are a variety of attack vectors as illustrated in the figure right. For protection, security is required on multiple levels, preferably at every network layer.

Find some recommended classes below. The full program is available here.

Tuesday 26th, from Communication – CAN

09:30 – 10:00 / Troubleshooting in Embedded Networks Based on CANopen FD
Reiner Zitzmann, CAN in Automation

10:00 – 10:30 / Automated Node ID Assignment in CAN and CAN(FD) Networks
Christian Keydel & Olaf Pfeiffer, Embedded Systems Academy

10:30 – 11:00 / Signal Improvement Concept for CAN FD Networks
Yao Yao, CAN in Automation

Tuesday 26th, from HW-based Security

12:00 – 12:30 / Extend MCU Security Capabilities Beyond Trusted Execution with Hardware Crypto Acceleration and Asset Protection
Saurin Choksi, NXP Semiconductors

15:00 – 15:30 / Methods for Provisioning Security Features in a Cortex-M33 based MCU Using A Physically Unclonable Function
Rob Cosaro, NXP Semiconductors

Wednesday 27th, from Architectures & Hacking

16:30 – 17:00 / Securing all Network Layers of CAN (FD) Communication
Olaf Pfeiffer, Embedded Systems Academy
Andreas Walz, Offenburg Univeristy

Meet us at Embedded World

During the show, you will find our tutors either at the CiA booth (hall 1, booth 630) with the CANopen FD Demonstrator or at the NXP booth (hall 4A, booth 220) featuring a Multi-Layer CANopen FD Security Demonstrator.

Over the past year, our authors Christian Keydel and Olaf Pfeiffer have published several security- related CAN articles in the CAN newsletter. It’s now time for an up-to-date summary, review and outlook.

How do we address security?

To analyze the application-specific attack scenarios, we can group systems with CAN-connected devices as follows:

• Private and locked:
  Only trusted persons have physical access to CAN wires and devices. There are no gateways to other networks.
• Remotely accessible:
  The CAN bus is connected to one or multiple gateways to other networks.
• Time-limited physical access:
  An untrusted party can be expected to have physical access to the CAN bus and devices for a limited time.
• Unlimited physical access:
  An untrusted party can be expected to continuously have physical access to the system.

What measures should be taken?

The recommended security measures for the mentioned groups range from none for group 1 to state-of-the-art for group 4 which presents the toughest challenge. With virtually unlimited physical access, an untrusted party can go as far as using flash/code extraction services for MCUs to obtain code and private keys. To thwart such attempts, you will have to use a secure microcontroller with built-in encrypted key and code storage like the NXP LPC54Sxx series for example. Here, the encryption is based on a private PUF (Physical Unclonable Function) which uses physical properties that vary for each chip and can never be extracted, like contents of uninitialized SRAM.

Securing CAN communications is a viable option especially for group 2 and in combination with physical protection also group 3 applications. As we’ve shown, it needs only minimal resources to implement injection monitoring in combination with a secure heartbeat (see article “Scalable CAN security”). However, due to the limited data size in CAN messages, individual message authentication often requires sending a second message with the authentication data.

With CAN FD, adding security becomes easier, as the payload and security record can often be combined in a single CAN FD data frame, avoiding the overhead of managing a second authentication message.

What can we expect in the future?

In the new CiA CAN Cyber Security group it has become clear that where security is required, it should be added to all communication layers.  To add message monitoring and flood protection to the CAN bus, there are hardware solutions like NXPs TJA115x secure CAN/CAN FD transceiver family. Similar protection can be added in software to the lowest driver layers. Just above the data link layer, CANcrypt (FD) provides a secure grouping mechanism. For the CANopen/CANopen FD and J1939 protocol layers, different security features can be implemented, including authenticated access for diagnostics or remote-control features.

Reaching highest security levels will only be possible if the hardware supports securing the software and communications, using built-in features for the protection of stored code and keys.

Today, Embedded Systems Academy published the first release of a free CANcrypt FD implementation for the NXP LPC54618 microcon-troller. CANcrypt FD is a security middleware, providing authentication and encryption for CAN FD. It uses an 8-byte security record, embedded in the 64-byte data field of CAN FD frames. The cipher to use is configurable – the examples use SPECK-64, XTEA-64 and AES-128.

The base security mechanism in CANcrypt FD is a secure heartbeat that cyclically generates a dynamic, shared key among the grouped devices. The device address / ID has now 8 bits, up from 4. While still only up to 15 devices can actively participate in the key generation, another up to 239 devices can passively update their keys to transmit and receive secure messages.

A new feature is the active initial grouping cycle. Similar to the pairing process, this mode allows the automatic grouping of devices during a first-time power-up of the network. The devices participating in the grouping process generate/negotiate a group key that is then kept in local non-volatile memory.

For more details, see our article No excuses for not securing your CAN FD communication in the current September 2018 CAN Newsletter or download the CANcryptFD NXP LPC54618 example implementation including documentation.

At the upcoming CiA cyber security workshop (Nuremberg, May 2nd) our engineers participate with two presentations. We inform participants about the most common attack vectors used on CAN (FD) systems and some of the basic protection mechanisms already available today. In a second part we will outline CANcrypt based mechanisms and how they can easily be used to implement a generic security layer. This layer can be used in between the CAN Data Link Layer and the higher protocol layers like J1939 or CANopen.

The cyber security workshop is free for CiA members. To register, visit the CiA web pages.

The new CANgineBerry is an active CAN interface with a Cortex-M0 microcontroller and various firmware options. At launch, two options are available: One for a CANopen Controller / Manager and one for a configurable CANopen slave device.

The CANopen Controller scans the network for connected slave devices within less than 50 ms after power-up, sets up process data handling, starts the network and continues monitoring it. Once the host that CANgineBerry is connected to is up and running as well, it can immediately start using the CANopen network and access any device.

The second firmware option is implementing a CANopen slave device which is fully configurable with node ID and with an Object Dictionary that the user creates with the provided CANopen Architect software (evaluation version is sufficient for this use).

The CANgineBerry’s host can be a Raspberry Pi®, another embedded computing systems or even a PC. The communication to the host system uses a regular serial channel (TTL-UART), so no special driver is required as UART support is typically part of all operating systems. The communication between host and CANgineBerry and the API is designed to serve the application. For example, heartbeats are automatically monitored but the host is only informed about changes in the heartbeat status (like “activated” or “lost”) but not about every individual heartbeat message.

This architecture of CANgineBerry addresses the shortcomings of many “CAN shields” that are passive, have no own intelligence and require the host computer to handle all CAN communication message by message. In worst case, a CAN system can have more than ten thousand individual messages per second. Sometimes the real-time requirements are below 10 ms for some responses which is not realistically achievable with a Linux or Windows® based host and a passive approach.

Summary of firmware options currently available or under development:

• CANopen self-configuring Controller / Manager
• CANopen slave device (configurable via EDS, Electronic Data Sheet)
• Lawicel CAN-RS232 protocol
• CANcrypt (secure CAN communication) for the above versions
• CiA 447 – automotive add-on electronics
• J1939 gateway

For more information about the CANgineBerry, current firmware options and availability, visit www.CANgineBerry.com

Some people try to push easily-available “Internet-proven security mechanisms” also into embedded networks like CAN and CANopen. However, in embedded systems security is never about a single network, one needs to look at the entire picture.

We have started a series of articles about embedded security issues with a focus on CAN and CANopen networks in the CAN newsletter. In the current article we are having a closer look at taxi fare calculation as one example for an attractive hacking target. How can you be sure that you are not overcharged? What would be required to make taxi fare manipulations really difficult?

Tampering with the underlying CAN/CANopen communication is just one of several attack vectors available here. Besides manipulating the wheel with the sensor – knowing that a 3% change in diameter can result in a 10% variance in the fare calculation – there is also the sealed meter. But these days, technology like 3D printers and sophisticated electronics are also easily being used by the “bad guys”. From the article:

“Think about the manipulations already performed today to banking machines. Additional keyboards and card readers can be tacked-on to banking machines in a way that users don’t recognize the difference. In the same way a meter-like display could be designed to clip onto or fully around an existing meter. The original meter “vanishes” inside a fake meter that can display whatever the taxi driver would like it to display.”

Browse the current CAN Newsletter: March 2018

Read the full article here: Security expectations vs.limitations (pdf)