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Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

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Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#161

Post by alttab »

vntok wrote: post #140
oh_sigh wrote: post #130

Earlier quoted context omitted.

Even finding a single double spend attack that only double-spends 1 satoshi would be enough to destroy bitcoin.

No it would not. Finding a BTC double spend attack vector would be like finding a 0-day: good and maybe even profitable up until fixed, which would take hours, days at most. Have 0-days destroyed Microsoft, Android, Firefox, Electron or Chrome?

So it's ok if your currency becomes unreliable for many hours? It would immediately negate the trust of what happened during that period of time, affecting the trust of any balance in participating addresses.

Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#162

Post by lend000 »

thaumasiotes wrote: post #155
bo1024 wrote: post #145

Earlier quoted context omitted.

Those are some really great and interesting points. However, I think there is a resource you didn't mention that combats such attacks: time. If I'm a vendor, e.g. I pay cash for bitcoin, then I can tune the amount of time the transaction is held in limbo or escrow based on the vulnerability of the network. For instance, I can decide not to finalize the transaction until I see a chain with 12 new blocks added after th…

> I see Bitcoin moving toward an intermediary system where you have a "Bitcoin balance" with a "Bitcoin bank" that allows you to make immediate transactions and takes on the risk and time delay of settling these transactions on the blockchain over the course of the next day or two. How would this system differ from an ordinary bank in the system we have now?

In our current system, we have centralized, government bank run clearing houses that you cannot use (which Bitcoin could hypothetically replace). For a Bitcoin-based financial system, you can opt to pay higher fees and clear transactions on your own, or store your wealth in your own wallets and take on the management effort and fees in exchange for autonomy.

Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#163

Post by josu »

zaroth wrote: post #148

So this would require an attacker to pay into the exchange with BTCg, have the deposit clear and approve for trading, trade it for another currency, and have that trade settle and be clear for withdrawal, and then process the withdrawal, all in under 4 hours. After which point the attacking miner surfaces a longer chain they had been keeping which doesn’t include the original BTCg deposit. Alternatively, if the excha…

Many people use exchanges for arbitrage. Exchanges benefit from arbitrage since they take a fee out of every trade and because they want their prices to be close to the international price of the asset.

This trade would look exactly the same as an arbitrage move.

Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#164

Post by Arbalest »

rpearl wrote: post #149
cachvico wrote: post #23

Earlier quoted context omitted.

Exactly. We should stop using the word "waste" to describe the energy consumption of the Bitcoin miners. It's not waste if it serves a purpose. The service it provides is to guarantee the integrity of the blockchain without the requirement of a central authority.

it is a waste. Bitcoin is an unqualified environmental catastrophe that is literally erasing any progress we've made to combat climate change. Burning away the future, turning useful energy purely and directly into waste and profit by shouting numbers into the void, not even leaving any artifact of value in its wake. There's not anything wrong with having a central monetary authority. There's not anything wrong with…

It could be argued that the trust could still be misplaced, but the idea that we can't trust governments for currency is barking up the wrong tree.

The fundamental problems of inequality don't stem from Treasury, but rather from the game theory concept of the https://en.wikipedia.org/wiki/Gambler%27s_ruin making barriers to entry for new players always higher than the incumbents. You can take this all the way down to the bottom, in the example of having no car to be a delivery driver, and to get a loan for a car is a tremendous risk.

Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#165

Post by icook »

XR0CSWV3h3kZWg wrote: post #6

more details here: https://forum.bitcoingold.org/t/double-spend-attack-on-excha... Bitcoin gold was a fork to try and decentralize mining. It changed to a proof of work that is supposed to be ASIC resistant. It looks like the typical situation is mining by GPU for equihash (BTG PoW). BTG hashrate is at ~30MH/s at the moment, where Zcash's hashrate is at ~486MH/s. I don't have the numbers off hand, but it'd be interes…

I was curious about the cost as well, so I ran some rough numbers.

417.5 BTC/GH/day for equihash if you're renting from nicehash [1]. Block interval 10 minutes [2]. 144 blocks per day target yields 0.0869 BTC/block, so cost of the 22 block reversal was ~1.91 BTC, or roughly $15k.

I'm curious if this was done as one large deposit, or many smaller deposits. I've imagined a system where block confirmations required are based on a computed cost of attack done like I did above, which would be pretty effective for very large single transaction double spends. A bit trickier to handle multiple deposits spread across multiple user accounts.

[1]: https://api.nicehash.com/api?method=simplemultialgo.info

[2]: https://bitcointalk.org/index.php?topic=2284289.0;all

Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#166

Post by thaumasiotes »

hobs wrote: post #86
arebop wrote: post #85

Earlier quoted context omitted.

Your biggest mistake is comparing energy use. You need to compare the total overhead of bitcoin to the total overhead of the competitive financial system. The second mistake is comparing a per-transaction basis; this is of interest when we are comparing suitability for particular applications, but if you want to talk more generally about whether bitcoin is efficient for payments you need to look at things on a value…

Why? Why does a new system need to be just as bad as the old one?

It doesn't.

But if the new system is better than the old one, why would comparing it to the old one imply that anyone using the new one should be ashamed of doing so?

Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#167

Post by vntok »

alttab wrote: post #161
vntok wrote: post #140

Earlier quoted context omitted.

No it would not. Finding a BTC double spend attack vector would be like finding a 0-day: good and maybe even profitable up until fixed, which would take hours, days at most. Have 0-days destroyed Microsoft, Android, Firefox, Electron or Chrome?

So it's ok if your currency becomes unreliable for many hours? It would immediately negate the trust of what happened during that period of time, affecting the trust of any balance in participating addresses.

If Visa or SEPA got hacked over 12 hours and then fixed the root cause, would you stop using credit cards or bank transfers altogether? I would not.

Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#168

Post by xur17 »

XR0CSWV3h3kZWg wrote: post #6

more details here: https://forum.bitcoingold.org/t/double-spend-attack-on-excha... Bitcoin gold was a fork to try and decentralize mining. It changed to a proof of work that is supposed to be ASIC resistant. It looks like the typical situation is mining by GPU for equihash (BTG PoW). BTG hashrate is at ~30MH/s at the moment, where Zcash's hashrate is at ~486MH/s. I don't have the numbers off hand, but it'd be interes…

You can rent hashing power on Nicehash, which currently has ~77MSol/s available for rent. I'm not 100% familiar with how the auction process works, but it looks like I could purchase 26MSol/s via a fixed contract for 1 hour for ~1BTC.

Am I misunderstanding something here, or can I maintain a 51% attack right now for ~$8k an hour. This can't be right.

Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#169

Post by thaumasiotes »

CydeWeys wrote: post #157
thaumasiotes wrote: post #155

Earlier quoted context omitted.

> I see Bitcoin moving toward an intermediary system where you have a "Bitcoin balance" with a "Bitcoin bank" that allows you to make immediate transactions and takes on the risk and time delay of settling these transactions on the blockchain over the course of the next day or two. How would this system differ from an ordinary bank in the system we have now?

It's still trustless, decentralized, yadda yadda.

In what sense is a system where you hold all your bitcoins in a "bitcoin bank" decentralized or trustless?

Re: Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose Millions

#170

Post by zitterbewegung »

tlarkworthy wrote: post #92
jhpriestley wrote: post #83

When Bitcoin was running up to $20,000, I tried to analyze the system and come to a personal conclusion about its equilibrium value, because I didn't want to miss out if it really was the currency of the future. I ended up not investing, because of the possibility of a double-spend attack. I think that cryptocurrency enthusiasts are seriously underestimating the importance of double-spending attacks to the economics…

I think the argument is that by doing a 51% attack you undermine the market value so you never get the rewards. This makes sense, but only for the leading crypto coin. As we see here today, you can 51% attack smaller coins, which should imply an increase in the value of Bitcoin from consolidation.

On certain exchanges you can short USD to cryptocurrency pairing.
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