Application Scenario

Goal

• Byzantine resilient
• Secure coordination: Swarm behaves exactly as specified
• Reaches consensus
• Without affecting the task execution time too much

Impacts

• Increases scalability: New members can be included at any time; their controllers can be obtained from the blockchain
• Increases autonomy: Robots behave exactly as specified without supervision
• Increases security: Attacker have little chance/incentive to maliciously influence the swarm behavior
• Increases transparency: All critical events are recorded in the blockchain

General properties for a application scenario

• Robots work remotely, without real-time supervision (e.g., deep sea, planetary exploration, or underground); they can only communicate in a peer-to-peer manner; there is no central trusted source of information
• The swarm should come to consensus; no robot should be able to do something without getting automatically punished or rewarded; robots (and, therefore, their owner) should have a guarantee that a certain action leads to certain consequences
• The swarm behavior should behave "exactly as specified" -> secure coordination (important for all sensitive tasks)
• Robots should be fully autonomous (no single point of failure, no one can just press a button and stop them, no person decides if a member is included in the swarm or not)
• The swarm should be able to add new members at any time (there is no need of password authentification, any robot can join)
• Robots possibly belong to different organizations (e.g., robot project collaboration between different countries, no country wants to face the risk that another country just stops the project)
• The swarm members are untrusted (you don't have to know which organization or person a robot belongs to; you don't have to know if a robot sends right or wrong information)
• Each robot is a (light) node in the network; they could verify and distribute transactions
• The blockchain does not need to be the only communication medium, instead it could be used for critical information only and complemented with "normal" local communication
• After a mission was performed, it might be imporant to see, which robot performed what action; thanks to the immutability of the blockchain, this can be done long time after the actual actions were performed
• These settings can be used in: exploration, mapping, oil spill removal, humanitarian demining

FAQ

• Q: Robots are computationally limited devices. Therefore, they can only perform proof-of-work (PoW) with limited difficulty. What happens if a much more powerful attacker performs a 51% attack?
  • Bitcoin's classical PoW might not be the right choice. Instead, proof-of-stake (PoS) might be a better alternative. The stake might be built by using "Physical PoW", for example by removing oil spills or mines.

• Q: How do light clients work with Ethereum/with your framework?
  • The development of suitable light clients could be a part of the research. Light clients for PoS still have to be developed.

• Q: Why do you use physical robot and not just simulation?
  • Simulations can never capture all aspects of the real-world
  • The goal is to pave the way for real-world robot task; physical robots provide a proof-of-concept
  • Allows to study "Physical proof of work"
  • It allows to directly study and the capability of the blockchain technology to handle failing sensors, actuators, and other unforeseen events

• Q: Why don't you just use a classicial consensus algorithm?
  • Other existing consensus algorithms (apart from blockchain technology) are susceptible to Sybil attacks or only provide consensus to a small degree

• Q: Why don't you use a authentification system to only include trusted members?
  • A classical authentification system can be easily compromised (e.g., once the password is revealed, the entire system breaks down)
  • The swarm is more flexible without a authentification system: everyone can join at any time

• Q: Why do you want to start your own blockchain instead of using the main Ethereum blockchain?
  • Since the robots work at remote areas, they may be without Internet connection for a long time.
  • Currently, there are no available light (thin) clients for Ethereum and the main blockchain is too memory-intense for small robots.

• Q: Why would new members join the swarm?
  • New members could join the swarm to replace broken members, to reduce the time for solving the problem, or to be able to solve the problem at all.

• Q: Ethereum and blockchain technology is already out there. What are your contributions?
  • Study possibilities and limitations of combining blockchain technology and robot swarms
  • Bring blockchain technology to smaller devices; study possibilities for light clients without proof of work
  • Provide proof-of-concept for robot swarms

• Q: How will you prevent physical attacks on the swarm (destroy robots, catch & release robots)?
  • Using inspiration from game theory, one could render beneficial behaviour more profitable than malicious behavior. Since the blockchain is tamper-proof, one can easily transfer "real money" to it (e.g., from another blockchain). B using certification methods, one could check if the robot has been "reprogammed" during captivity.

• Q: Does your thesis also contribute if one does not want to start a new blockchain?
  • Yes. I will develop protocols for light (thin) clients that work on limited devices.
  • I will develop methods for sparse communication.
  • ...

• Q: Is this really swarm robotics or rather a multi-robot system?