Bitcoin.org defines a 51 percent attack as “the ability of someone controlling a majority of network hash rate to revise transaction history and prevent new transactions from confirming.” It’s simple straight to the point and self-explanatory. As simplified as it is, the majority attack is dreaded by the community and at the height of last year’s bitter hash rate war between Bitcoin Cash factions—the ABC and SV camps, the latter threaten to unleash fury and destroy ABC via a 51 percent attack now that they had control of 57 percent of the Bitcoin Cash network before the value wiping hard fork on Nov 15.
However, hours into the upgrade, Roger Ver’s Bitcoin.com mining pool hash rate shot to 4 Exahash and surpassing the entire Bitcoin Cash network hash rate. But even before the upgrade, odds were stack against Craig Wright and his supporters because of Bitmain inclination. With Jihan Wu on their side and revelation by Jiang Zhuoer, the CEO of BTC.TOP that “mining pools under Bitmain (such as BTC.com and Antpool) collectively had15,000 P hash-rate. With ViaBTC where Bitmain is a shareholder, the entity has 20,000 P hash-rate altogether”, it remain a tight and tense race.
Blockchain supporters have to protect their turf and the best way of doing so especially in a proof of work consensus network where ASIC miners are involved is to marshal participation and increase computer power within the network. A vibrant, well incentivized mining community means faster transaction processing and a secure network that to some degree is resistant to a majority attack. Note that a vulnerable network is lost man hours and after Ethereum Classic had an encounter with determined attackers, it was time developers went to work designing a new protocol that is not only secure but makes such an attack extremely expensive.
DASH and ChainLocks
Dash through their Dash Improvement Proposal (DIP)-8 suggest a use of “long-living Masternodes quorums (LLMQs)” in ChainLocks to deter possible network disruptions stemming from a 51 percent attack. The LLMQ signs blocks, prevents attempts of transaction reversal and generally protects the network ensuring that a mining-based attack on the DASH network is “impossible.” What’s unique is that this measure is only specific to DASH thanks to their masternodes structure that effectively wades off attempts of Sybil attacks that other crypto networks are prone to.
“The idea of ChainLocks is to perform a verifiable network-wide measurement/vote of the “first-seen” rule. For each block, an LLMQ of a few hundred masternodes is selected and each participating member signs the first block that it sees extending the active chain at the current height. If enough members see the same block as the first block, they will be able to create a P2P message (CLSIG) and propagate it to all nodes in the network.”
But it is not the network that draws most benefits, it is the end user who can trust that every transaction is valid even after the first signature.
“The most important effect for normal users and merchants is that transactions can be considered fully confirmed after the first on-chain confirmation inside a block protected by ChainLocks. Transactions can no longer vanish from the chain since reorganization of signed/locked blocks is not possible.”
RepuCoin Introduces Miner Reputation
Another way to squash 51 percent attacks is the introduction of “reputation” in blockchain projects like what RepuCoin is doing. Developed by the University of Luxembourg’s Interdisciplinary Centre for Security, Reliability and Trust, voting power, that is, reputation, is based on mathematics and the miner’s mining power and consistency. As a result, the longer RepuCoin remain secure, the more resilient it becomes making it impossible. Researchers quantify that a 51 percent attack at RepuCoin that has been running securely for one year, with a 68 percent control of the network hash rate, will take six months and is 5760 times more expensive that it would have been on the Bitcoin network.
The Co-author of RepuCoin Prof. Paulo Esteves-Veríssimo says:
“It’s an elegant solution to a problem that was thought as 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.”