Blockchain for safety-critical interlocking logic
Blockchain makes it possible to run several computers in a network and thus increase reliability. Particularly in safety-critical areas such as signal boxes, this enables the use of standard computers where special hardware would otherwise have to be used. In the TARO project, SCS has developed a concept and prototype for the use of blockchain for interlocking logic.
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Initial situation
Safety-critical components are expensive because they require special hardware and the development must fulfil strict guidelines.
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SCS solution
Security-critical logic is transferred to a private blockchain as a smart contract. The private blockchain serves as a secure system that fulfils the high reliability requirements.
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Added value
Costs can be saved by combining "standard" blockchain technology and "standard" computers. Once such a system is certified, only the smart contract needs to be certified.
Project insights
When designing a blockchain solution, it is important to ensure that the blockchain is only used for those aspects that are absolutely necessary. In our case, for those aspects that are security-critical. What is not or less security-critical can be implemented with technologies that have a higher throughput, larger memory and lower development costs.
In our case, it has been shown that a simple reservation system is the minimum solution that fulfils all requirements. For each train, the track sections, points, level crossings, … are reserved well in advance for each train. The reservation includes in particular the position of the component (e.g. the points). This reservation is the digital form of a green signal. The train checks whether it has the reservation for the next track section and therefore knows whether it is authorised to use it. If the blockchain says “no” or it loses the connection to the system, this corresponds to the red signal. The train must stop.
Other information is not managed via the blockchain. For example, the topology information (how the track sections and switches are connected) is not on the blockchain. The “operational state” is also important. If you want to know the current status of a component, a blockchain is reliable, but not fast. We have therefore added the “operational state” as an additional layer, which corresponds to a veto right. In concrete terms, this means that the train only runs over the switch if the blockchain and the switch itself say “yes”. If one of them says “no”, this corresponds to a red signal.

In addition to the concept, SCS has built a prototype of the blockchain and a simulator, which together show that the system works:
The concept and demonstrator were discussed with experts from ÖBB Infrastruktur AG and other project partners and were considered a sensible solution by all parties. Performance measurements were also carried out, which show that the performance is sufficient for the regional railway sector.
Until blockchain is actually used productively for safety-critical logic, there are certainly still a few hurdles to overcome. One of the most important questions is how blockchain can be certified for security-critical applications. In terms of its basic principle, blockchain has exactly the properties we need for a reliable, tamper-proof system. At the same time, it is a new technology where a lot is still in flux. Nevertheless, we see a lot of potential for the use of private blockchains for reliable systems.
About the Taro project
The TARO (“Towards Automated Railway Operation”) project is a multi-year research and development project led by the ÖBB Group. Together with 17 partners, numerous aspects relating to the digitalisation and partial automation of the entire railway system are being worked on. One of the focal points of the project is “Regional railway technology of the future”. The Federal Ministry for Climate Protection, Environment, Energy, Mobility, Innovation and Technology (BMK) is funding the project with a total of EUR 3.5 million from the RTI programme Mobility of the Future, which is managed by the Austrian Research Promotion Agency (FFG). Further information can also be found at konzern.oebb.at/en/taro.

