Blockchain technology could provide secure communications for robot
teams

Date:
October 5, 2021
Source:
Massachusetts Institute of Technology
Summary:
The use of blockchain technology as a communication tool for a team
of robots could provide security and safeguard against deception,
according to a new study. The research may also have applications in
cities where multirobot systems of self-driving cars are delivering
goods and moving people across town.



FULL STORY ========================================================================== Imagine a team of autonomous drones equipped with advanced sensing
equipment, searching for smoke as they fly high above the Sierra Nevada mountains. Once they spot a wildfire, these leader robots relay directions
to a swarm of firefighting drones that speed to the site of the blaze.


==========================================================================
But what would happen if one or more leader robots was hacked by a
malicious agent and began sending incorrect directions? As follower
robots are led farther from the fire, how would they know they had been
duped? The use of blockchain technology as a communication tool for a
team of robots could provide security and safeguard against deception, according to a study by researchers at MIT and Polytechnic University of Madrid, which was published today in IEEE Transactions on Robotics. The research may also have applications in cities where multirobot systems
of self-driving cars are delivering goods and moving people across town.

A blockchain offers a tamper-proof record of all transactions -- in this
case, the messages issued by robot team leaders -- so follower robots
can eventually identify inconsistencies in the information trail.

Leaders use tokens to signal movements and add transactions to the
chain, and forfeit their tokens when they are caught in a lie, so this transaction-based communications system limits the number of lies a hacked robot could spread, according to Eduardo Castello', a Marie Curie Fellow
in the MIT Media Lab and lead author of the paper.

"The world of blockchain beyond the discourse about cryptocurrency has
many things under the hood that can create new ways of understanding
security protocols," Castello' says.



==========================================================================
Not just for Bitcoin While a blockchain is typically used as a secure
ledger for cryptocurrencies, in its essence it is a list of data
structures, known as blocks, that are connected in a chain. Each block
contains information it is meant to store, the "hash" of the information
in the block, and the "hash" of the previous block in the chain. Hashing
is the process of converting a string of text into a series of unique
numbers and letters.

In this simulation-based study, the information stored in each block
is a set of directions from a leader robot to followers. If a malicious
robot attempts to alter the content of a block, it will change the block
hash, so the altered block will no longer be connected to the chain. The altered directions could be easily ignored by follower robots.

The blockchain also provides a permanent record of all transactions. Since
all followers can eventually see all the directions issued by leader
robots, they can see if they have been misled.

For instance, if five leaders send messages telling followers to move
north, and one leader sends a message telling followers to move west, the followers could ignore that inconsistent direction. Even if a follower
robot did move west by mistake, the misled robot would eventually
realize the error when it compares its moves to the transactions stored
in the blockchain.



========================================================================== Transaction-based communication In the system the researchers designed,
each leader receives a fixed number of tokens that are used to add
transactions to the chain -- one token is needed to add a transaction. If followers determine the information in a block is false, by checking
what the majority of leader robots signaled at that particular step,
the leader loses the token. Once a robot is out of tokens it can no
longer send messages.

"We envisioned a system in which lying costs money. When the malicious
robots run out of tokens, they can no longer spread lies. So, you can
limit or constrain the lies that the system can expose the robots to," Castello' says.

The researchers tested their system by simulating several
follow-the-leader situations where the number of malicious robots
was known or unknown. Using a blockchain, leaders sent directions to
follower robots that moved across a Cartesian plane, while malicious
leaders broadcast incorrect directions or attempted to block the path
of follower robots.

The researchers found that, even when follower robots were initially
misled by malicious leaders, the transaction-based system enabled
all followers to eventually reach their destination. And because each
leader has an equal, finite number of tokens, the researchers developed algorithms to determine the maximum number of lies a malicious robot
can tell.

"Since we know how lies can impact the system, and the maximum harm that
a malicious robot can cause in the system, we can calculate the maximum
bound of how misled the swarm could be. So, we could say, if you have
robots with a certain amount of battery life, it doesn't really matter
who hacks the system, the robots will have enough battery to reach their
goal," Castello' says.

In addition to allowing a system designer to estimate the battery life
the robots need to complete their task, the algorithms also enable the
user to determine the amount of memory required to store the blockchain,
the number of robots that will be needed, and the length of the path
they can travel, even if a certain percentage of leader robots are hacked
and become malicious.

"You can design your system with these tradeoffs in mind and make more
informed decisions about what you want to do with the system you are
going to deploy," he says.

In the future, Castello' hopes to build off this work to create new
security systems for robots using transaction-based interactions. He
sees it as a way to build trust between humans and groups of robots.

"When you turn these robot systems into public robot infrastructure,
you expose them to malicious actors and failures. These techniques are
useful to be able to validate, audit, and understand that the system is
not going to go rogue.

Even if certain members of the system are hacked, it is not going to
make the infrastructure collapse," he says.

The paper was co-authored by Ernesto Jime'nez and Jose' Luis Lo'pez-Presa
of the Universidad Polite'cnica de Madrid. This research was funded
by the European Union's Horizon 2020 Research and Innovation Program,
the Regional Government of Madrid, and the MIT International Science
and Technology Initiatives Global Seed Fund.

========================================================================== Story Source: Materials provided by
Massachusetts_Institute_of_Technology. Original written by Adam
Zewe. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Eduardo Castello Ferrer, Ernesto Jimenez, Jose Luis Lopez-Presa,
Javier
Martin-Rueda. Following Leaders in Byzantine Multirobot Systems
by Using Blockchain Technology. IEEE Transactions on Robotics,
2021; 1 DOI: 10.1109/TRO.2021.3104243 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211005175428.htm

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