Bitcoin Gold (BTG) was 51% attacked

btg-attacks.md

Bitcoin Gold (BTG) was 51% attacked

Preamble

Bitcoin Gold is a Bitcoin hard-fork that aims to be GPU-mineable by using the Equihash algorithm with parameters (144, 5) also known as "Zhash". The Bitcoin Gold website claims Zhash "uses more memory than an ASIC can muster, but runs fine on many graphics cards". Bitcoin Gold was previously 51% attacked in May 2018 when it was estimated that up to $18 million worth of BTG was double-spent.

The Attacks

Between Thursday and Friday we detected two deep reorgs on BTG, both of which contained double-spends. Their details are listed below. All times are GMT.

• Thu, 23 Jan 2020 18:01:32 - 14 blocks removed, 13 blocks added
  • 1,900 BTG double-spent (~$19,000).
  • 1,900 BTG originally sent to GgmzUSgXrXpDxiY34bG6SxaDVi2rQ1zU8Q in TXID 3a17157994502a749a1827883a670d822f8ee95dae94064631770faeec1e8443 was redirected to GNH5cUEg5LZZP5HfLgaLvTE9ApKAf76aBf in TXID 6e05e8253b2ce7f1acf6f0684898e13141c0e9b893e1a5e44d215d8ebe4d28b4.
  • The majority of the coins were sent from an output owned by the address GK6HuN964f3XFScY5CPGg1oZ1gFRq52nf5.
• Fri, 24 Jan 2020 00:24:08 - 15 blocks removed, 16 blocks added
  • ~5,267 BTG double-spent (~$53,000).
  • ~1,947 BTG originally sent to Gg4YDMrMuqit6eJAYKaBxmK17zPFnpLt5w, 1,850 BTG to GfRdNzHJan8sfW9wxozAYhRPL9fFLD9A9m in TXID 481d608591f4d6a7013ac1b879c2caf1e2c0a2bb30b5346b2c876deb43873b2b and 1,470 BTG to GfWUNAdW3aEXfQWshApFLf2ZNtMV9MC6VQ in TXID 37c8a8d59f61879cc0da9fa197ed72dbc967c796800d4015cafd47c7be467201 was redirected to GPTH48Z3diz4zwBGchXmzW3kDnmHVxyX2V in TXID a0dc721fff0948732679638f4b4bb713686786826971c3f9a30eb15f5694a0ea.
  • The majority of the coins were sent from outputs owned by the address Gdc4ANNdqyGBadobzUDZNydBgDHAYdMeAb.

In both cases the attacker blocks were mined with the address GWrW5dTZf5XwGWoJuqRKdzkzZFkwtWSqaP in the coinbase transaction. We note that at the time of the attack, on Binance deposits of BTG were credited to one's account for trading after six confirmations, and were available for withdrawals after twelve confirmations. A fourteen or fifteen block reorg would thus evade both of Binance's escrow periods. Binance has since increased their withdrawal requirement for BTG to twenty confirmations. 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.

I didn't have time to thank you earlier - so, thanks for the work and contribution of information.

Note, this part has an error:

1,900 BTG originally sent to GgmzUSgXrXpDxiY34bG6SxaDVi2rQ1zU8Q in TXID 3a17157994502a749a1827883a670d822f8ee95dae94064631770faeec1e8443 was redirected to GgmzUSgXrXpDxiY34bG6SxaDVi2rQ1zU8Q in TXID 6e05e8253b2ce7f1acf6f0684898e13141c0e9b893e1a5e44d215d8ebe4d28b4.

Should read:

1,900 BTG originally sent to GgmzUSgXrXpDxiY34bG6SxaDVi2rQ1zU8Q in TXID 3a17157994502a749a1827883a670d822f8ee95dae94064631770faeec1e8443 was redirected to GNH5cUEg5LZZP5HfLgaLvTE9ApKAf76aBf in TXID 6e05e8253b2ce7f1acf6f0684898e13141c0e9b893e1a5e44d215d8ebe4d28b4.

@MentalNomad indeed, it has been fixed! Thanks!

Exchanges need to dynamically set number of confirmations required based on order book depth and network difficulty.

Exchanges need to dynamically set number of confirmations required based on order book depth and network difficulty.

I very much agree - I've advocated for that since 2018. Also, they need to consider the size of the deposit a factor. (You may have omitted that as obvious.) I find it remarkable how many exchanges will reply, "our system simply doesn't work that way" when you just ask that larger deposits be treated differently than small ones. But we'll keep trying.

Exchanges need to dynamically set number of confirmations required based on order book depth and network difficulty.

Here's another idea: stop this pointless exercise. Whatever rules you tack on and workarounds you implement, Bitcoin Gold/Cash/SV/Diamond/etc. will always be fragile and never worthwhile. You will only make people lose money, either through the market or attacks like this.

Exchanges need to dynamically set number of confirmations required based on order book depth and network difficulty.

Here's another idea: stop this pointless exercise. Whatever rules you tack on and workarounds you implement, Bitcoin Gold/Cash/SV/Diamond/etc. will always be fragile and never worthwhile. You will only make people lose money, either through the market or attacks like this.

You're conflating Gold/Diamon (airdrops with different POW) with valid forks stemming from contentious protocol changes (Cash/SV).

You're conflating Gold/Diamon (airdrops with different POW) with valid forks stemming from contentious protocol changes (Cash/SV).

An utterly meaningless distinction.

You're conflating Gold/Diamon (airdrops with different POW) with valid forks stemming from contentious protocol changes (Cash/SV).

An utterly meaningless distinction.

Attackers may actually use risk/reward assessment before picking a target, so there could also be a reason why bgold has horrible record so far, while others do not.

That’s a second attack, don’t understand what do you waiting to protect yourself with Komodo’s delayed Proof of Work (dPoW)???

Exchanges need to dynamically set number of confirmations required based on order book depth and network difficulty.

Here's another idea: stop this pointless exercise. Whatever rules you tack on and workarounds you implement, Bitcoin Gold/Cash/SV/Diamond/etc. will always be fragile and never worthwhile. You will only make people lose money, either through the market or attacks like this.

The idea is valid for any PoW coin. There are a lot of vulnerable coins in the same way. Order book depth / Incoming total deposits at any given time / network difficulty based confirmation requirements can be determined for any coin, and it protects the exchange and the customers. If you have a statistical model to decide which coins are not worth the time, you also have a statistical model to prevent these attacks by dynamically adjusting confirmation requirements.

Forking off from bitcoin is either economically motivated (read: scam), or at best a vote of no confidence in the current development process. So far, any such vote ended in a landslide victory for bitcoin developers (for good reason).

Starting a coin from scratch is also either economically motivated (read: scam), or at best technologically justified. As in: building something that's fundamentally better than bitcoin. If it's the latter, projects borrowing 99% of bitcoin's codebases should immediately raise a red flag. Also, most of the time these kinds of projects are trying to get rid of PoW as their main selling point.

So yes, the idea is valid for any PoW coin that tries to compete with BTC: they're a waste of everyone's time and money.

I think the solution to the “51% attack” problem can be found in this thread: https://bitcointalk.org/index.php?topic=5215111.0

OK, but BTG didn't "fork off from bitcoin."

BTG stood up a completely independent network with new nodes and new miners. It was impossible (by design) for Bitcoin miners to follow the BTG fork, which required entirely different hardware. There was exactly zero contention within Bitcoin as to whether to support Bitcoin or BTG.

BTG did fork Bitcoin's blockchain history as a fair basis for the initial distribution of 16.5 million BTG, true. But there was never contention or competition with Bitcoin, so there is no "landslide victory" or loss.

There was even a 20-day pause between the blockchain snapshot and the first BTG block. I don't see how this can be viewed as a competition.

Snapshot of BTC blockchain: October 23, 2017, block 491407
First BTG block mined: Nov 12, 2017, block 491408

Now I read the comments of 2019, when many did not take seriously and did not think that bitcoin would reach the price of 40 k dollars, not to mention 64 k)) Times have changed and now cryptocurrencies have caught up with the authorities very quickly and very well. Elon Musk and other millionaires, billionaires have started to invest very large amounts of money in cryptocurrencies, and this leads to higher prices. I personally invested on https://yuanpaygroup.com platform 10 k dollars in several cryptocurrencies and now I am waiting for growth. I have expectations of a minimum profit of $ 20k, but I hope it will be more. I am waiting ))

I didn't have time to thank you earlier - so, thanks for the work and contribution of information. by The way Twisting is possible in Cyrptocurrsy