One of crypto’s most feared assaults could have a sublime answer.
At least, that is in accordance to the crew behind cryptocurrency mission Horizen – formally zencash – which misplaced greater than $500,000 in such an assault, known as a 51 p.c assault, earlier this year.
This attack happens when one single malicious miner controls greater than 51 p.c of the compute energy on a blockchain community and may then inject false transactions into the system.
In a paper released today, the Horizen crew declare to have discovered an modern answer – by updating their proof-of-work consensus algorithm with a so-called “delay function” that penalizes miners that could possibly be getting ready for such an assault. Horizen is a fork of privacy-oriented crypto zcash, which is itself a fork of bitcoin.
Because a 51 p.c assault requires a miner to produce blocks in secret earlier than posting them to the blockchain, co-founder of Horizen Rob Viglione mentioned a delay perform permits for penalties that make such assaults prohibitively costly.
“So what it does is essentially it poses a massive cost, a 10x cost, on trying to launch one of these attacks,” he advised CoinDesk.
Stepping again, the 51 p.c assault has been part of many crypto fanatic’s consciousness this yr, after 5 main cryptocurrencies misplaced cash due to the assault in June.
Because they injury the arrogance within the safety of cryptocurrencies extra broadly, Viglione described such assaults as a “negative externality on the entire industry.”
And with direct perception into the assault – the 51 p.c assault on Horizen resulted in 36 faux blocks being included within the blockchain – Viglione mentioned:
“Right after the attack our engineers started brainstorming and we think we have a very elegant, simple solution to make sure that this doesn’t happen again.”
He continued, “Technically, to make it costly if it were ever to happen again.”
To do that, Horizen’s new algorithm introduces penalties for delayed blocks – these which are broadcast to the community a very long time after the newest block.
In impact, the brand new code launch modifies a characteristic of the underlying consensus algorithm, the so-called “longest chain rule,” with a delay perform.
For instance, if a block is proposed that’s 5 blocks or extra behind the newest, a penalty is launched, Viglione mentioned. That quadratically will increase the quantity of blocks a miner wants to produce so as to have transactions accepted onto the chain, he continued.
As such, the possibilities of a 51 p.c assault are decreased.
And due to the character of Horizen’s structure, such a penalty ought to solely happen if the miner is malicious, Viglione mentioned.
“We have an average block find time of 2 and a half minutes, maximum latency to broadcast anywhere in the world is like one or two seconds, so there’s no way you could be 5 blocks behind legitimately,” he defined.
This although, Viglione famous, might trigger a community partition to happen on the blockchain, as a number of chains of blocks compete to be acknowledged because the trustworthy chain. In this case, Viglione mentioned miners will vote to decide which chain is legit.
“They essentially elect which chain is legitimate and they start mining on that just like they would any longest chain rule,” Viglione mentioned.
Additionally, to stop such community splits from being everlasting, Viglione mentioned that penalties lower on the accepted chain.
“Blocks are added and there’s a negative one decrement to the penalty that was previously assessed, so there’s always a convergence that can happen to prevent the network partition being permanent,” he advised CoinDesk.
An age outdated query
Accompanying the discharge, a white paper states that ought to a series of blocks be rejected due to being too far behind the newest block, exchanges can freeze suspicious deposits till the scenario is resolved.
Additionally, Viglione mentioned the specifics of the penalties will be tweaked relying on community situations.
“We can tune and dial up the cost if we ever think it’s insufficient relative to hashrates and all that,” he advised CoinDesk.
Still, it is price noting that such modifications have lengthy been the topic of analysis, and others are skeptical about whether or not Horizen can obtain its claims.
For instance, main ethereum proof-of-stake researcher Vlad Zamfir famous that whereas he had but to dig into Horizen’s new code, “the design space doesn’t include miracles.”
Additionally, consensus researcher Emin Gur Sirer expressed skepticism, telling CoinDesk, “these protocols are subtle and difficult to get right.”
But, following a number of months of testing, Viglione is assured that the brand new algorithm works properly in observe, and hopes it may possibly set an instance for the broader cryptocurrency trade.
“We’ve been testing it internally for a little while now, a couple of months, so we’re pretty confident with the code,” Viglione mentioned, including:
“I’d imagine that other projects should, they really should update their code as well.”
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