A current thread about 51% attacks is here: <a href="https://news.ycombinator.com/item?id=22160523" rel="nofollow">https://news.ycombinator.com/item?id=22160523</a>
ELI5:<p>Lots of cyptocurrencies use the same mining algorithm, i.e. they require the same type of puzzle to be solved to make money creating blocks. In recent years, lots of online services have sprung up to offer cloud mining, which people usually use to mine blocks on the bigger cryptocurrencies, like Bitcoin Core or Bitcoin Cash.<p>However, since the smaller cryptocurrencies, like Bitcoin Gold, have less users/miners, they also require easier "puzzles" to be solved, which opens an opportunity for any random person to pay some $$$ to hire a bunch of these cloud servers for a limited time and point them at these easier puzzles, which can cause such a smaller blockchain to get confused about account balances. The attacker can then re-spend the same currency multiple times to make a profit.<p>AFAIK there aren't really any good solutions to prevent this problem- For complex game-theoretic reasons, simply changing the mining algorithm to something different doesn't really offer much protection. (Some folks believe if these smaller currencies were to move to "proof of stake" it could help solve this problem, but this is an extremely contentious topic.)
Since the other post got buried in a subthread: This is about Bitcoin Gold, not Bitcoin itself.<p>Bitcoin Gold is the least relevant of the forks (worth ~$12 per coin while the main chain BTC is worth ~8750 and the two major forks BCH/BSV are worth around 300, and only 7 of the 20 largest exchanges (by liquidity, according to coinmarketcap) list it - even though most of them list plenty of altcoins/shitcoins. For comparison, Bitcoin Cash is listed on all of them, Bitcoin SV on 14 of them. Additional stats here: <a href="https://news.ycombinator.com/item?id=22160458" rel="nofollow">https://news.ycombinator.com/item?id=22160458</a>
> He then provided a screenshot showing that Binance had since increased their BTG withdrawal requirement to 20 confirmations.<p>The journalist has missed an important part of the github gist that their story bases on:<p>> Based on Nicehash market price data for Zhash we estimate the cost of generating each reorg at around 0.2 BTC (~$1,700) and the attacker would have recouped around the same value in block rewards. Therefore, it is possible that the attacks were profitable if the double-spends succeeded at defrauding the attacker's counterparty, or break-even if the double-spends were unsuccessful. This suggests that a confirmation requirement on the order of tens of blocks for BTG is still far too few to make the budget constraint to launch an attack significant.
Second time this has happened to BTG. Boggles the mind that people continued to use this coin. <a href="https://fortune.com/2018/05/29/bitcoin-gold-hack/" rel="nofollow">https://fortune.com/2018/05/29/bitcoin-gold-hack/</a>
Note there are plenty of other cryptocurrencies that are susceptible.<p><a href="https://www.crypto51.app/" rel="nofollow">https://www.crypto51.app/</a>
Meta: I spend a lot of time in crypto(currency) subreddits, and of course approach those conversations differently than I do when I see the same topics pop up on HN. That said, I see a lot of the Reddit-style comments and terminology ("altcoins", "shitcoins", derisive names, etc) show up where when there's a crypto discussion. Does this happen in other subjects and I'm just unaware of those topic's subcultures? Or am I correct that the level of discourse for crypto is that much lower?
How disconnect the market is from facts. Price of Bitcoin Gold is not even affected by this news at all<p><a href="https://www.coingecko.com/en/coins/bitcoin-gold" rel="nofollow">https://www.coingecko.com/en/coins/bitcoin-gold</a><p>The market may not even understand what 51% is about
Just an observation: 51% attacks are happening there days in some countries in governments. When 51% gives you the absolute power in a bitcoin, it gives you enough to rule a country and push it to 100% (there are a few real life examples). Maybe 51% is a threshold too low for some things.
> Binance had since increased their BTG withdrawal requirement to 20 confirmations.<p>Perhaps they should require some multiple of (amount of the transfer / cost of the hashpower needed to mine one block)?
One point nobody is hitting on is that the price of BTG pumped a few weeks ago for no apparent reason. I guess we know why now. Pump the price and then attack it for even more profit.
The block which includes double-spent is invalid. When an honest node chooses the "strongest" chain it should check block If it's valid, not just look at a number of confirmations.<p>This is also true for blockchain browsers(and their api), which apps use to confirm the transaction(most of users don't run full node). The only way how 51% attack can be successful in the long term is that honest nodes(and blockchain browsers api) are re-configure to ignore double-spent(at least for a particular time period).
BTG might collapse as a result.<p>This might help general awareness that minor coins without a differentiating technology are simply highly vulnerable uninteresting clones, not worth any attention and thus, value. Perhaps some would just disappear, in a spiral of lower value, lower hash rate, more vulnerability, till all miners leave towards other, stronger coins?<p>This might sanitize the whole cryptocurrency domain a little.<p>Or not?
1 for 1 so far on my 2020 decade predictions<p><a href="https://news.ycombinator.com/item?id=21943830" rel="nofollow">https://news.ycombinator.com/item?id=21943830</a>
I wonder why this ended up in the front page of HackerNews? It's not news that altcoins are much much easier to attack than the top coin(s). Lesson to learn here: top coins are not only better due to the network effects (users and developers), they are also better in terms of security (it's much more expensive to carry out an attack in BTC or ETH, for example).