Researchers Using Reputation to Secure Blockchain Against ’51 Percent’ Attacks

Researchers at Monash University are part of an international team that has developed a blockchain system that can defend against malicious activity by attackers — even if they possess more than half of the chain’s computing power.

The system, RepuCoin, introduces the concept of ‘reputation’ to blockchain, effectively making it thousands of times more expensive to attack than conventional blockchains like Bitcoin. It also has the potential to be applied in a number of global sectors including fintech, energy, food supply chains, health care and future 5G telecommunications networks.

The new development also has the capacity to take more than 10,000 transactions per second. On average Visa processes roughly 1700 transactions per second. Researchers are now engaging with a number of international bodies which have expressed interest in rolling out this blockchain across their networks to maintain data security and integrity.

RepuCoin was developed Dr Jiangshan Yu (Monash University), Dr David Kozhaya (ABB Corporate Research Switzerland), Dr Jeremie Decouchant and Professor Paulo Esteves-Verissimo (University of Luxembourg) in response to an increasing number of sophisticated attacks on other blockchain by determined attackers.

Lead researcher and Lecturer in Monash University’s Faculty of Information Technology, Dr Yu, said RepuCoin is the only type of blockchain currently on the market that can withstand potentially devastating “51 percent” attacks.

Such attacks can occur when attackers rent coin mining capacity to obtain a majority of the blockchain’s computing power at any  point in time. Because blockchain operates by treating as genuine transactions or other changes that are accepted by a majority of the distributed computers that make up the network,  a successful 51 percent attack could impose fraudulent transactions, or worse even rewrite past transactions.

RepuCoin defines a miner’s power by its ‘reputation’, as a function of its work integrated over the time of the entire blockchain, rather than through the gross amount of computing power which which it controls at any particular moment. When a miner goes outside the boundaries of system specification, RepuCoin automatically lowers the miner’s reputation to prevent any malicious activity without significant consequences.

“But make no mistake, this is not about subjective reputation in the sense of social networks; it is about physics,” Professor Esteves-Verissimo said.

“Voting power takes time to build, accumulating through consistent and honest mining work. It’s like charging a battery before being able to use it.

“RepuCoin provides an elegant solution to a problem that many thought was insoluble. Existing systems always linked computational power to voting power. We separated them and now someone could join RepuCoin with 99% of the total computing power and they still wouldn’t be able to attack it.”

“When RepuCoin has operated for a year, attacking the system with 68% of its total mining power would take at least six months and would be at least 5760 times as expensive as conducting the same attack on Bitcoin,” Dr Yu said.

“And because of the way reputation accumulates, the longer RepuCoin runs, the more resilient it is to attack. For example, when the system has been in secure operation for only three months, an attacker would need to harness 90% of the overall computing power for a further month to behave maliciously.”

Read more at Monash University

The Government Technology & Services Coalition's Homeland Security Today (HSToday) is the premier news and information resource for the homeland security community, dedicated to elevating the discussions and insights that can support a safe and secure nation. A non-profit magazine and media platform, HSToday provides readers with the whole story, placing facts and comments in context to inform debate and drive realistic solutions to some of the nation’s most vexing security challenges.

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