Blockchain Denial of Service (BDoS)
"Cornell University researchers, in conjunction with the Initiative for Cryptocurrencies & Contracts (IC3) announced, “We have discovered a denial-of-service attack on Bitcoin-like blockchains that is much cheaper than previously described attacks. Such blockchains rely on incentives to provide security. We show how an attacker can disrupt those incentives to cause rational miners to stop mining.”
“We analyze the miner behavior as a game with iterated elimination of strictly dominated strategies (IESDS),” finding “an attack on Bitcoin-like cryptocurrencies requires as little as 20% of the mining power. The situation is even worse if miners can use their equipment in another blockchain rather than turn it off.”
Our attack, called Blockchain DoS (BDoS), exploits miners’ rationality by awarding them higher profit for playing against the system than following its rules,” researchers stressed. Getting honest or rational miners to stop, “the attacker generates a block and publishes its header, and only its header,” leading three alternatives for rational miners: extend the chain while ignoring the header, extend the block header, or stop altogether as a way to lessen on-going and futile power costs.
In extending the chain, broadcasting the next block, “the attacking miner uses his relatively high connectivity (as in selfish mining) and propagates the full block corresponding to the header BA. This causes a race between two groups of miners, those that hear of the attacker’s block data first and those that hear of the rational miner’s block first.” Extending the header, the attacker simply refuses to publish the full block, preventing it from being included in the main chain and, thus, no block reward. The final option, then, for a rational miner is to quit.
The BDoS attack, researchers acknowledged, is not imminent. Still, they believe it “is a threat to Nakamoto-consensus blockchains, as it allows denial-of-service with a much smaller hash rate than previous attacks.” And without addressing its potential, the paper claims, “the liveness of Nakamoto blockchains relies on miners’ willingness to follow the protocol despite revenue loss — that is, on altruism.”"
