News for hackers. Stuff that matters.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by oh_sigh on Wednesday May 23, 2018 @07:15PM (#17139352)
Even finding a single double spend attack that only double-spends 1 satoshi would be enough to destroy bitcoin.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by vntok on Wednesday May 23, 2018 @07:34PM (#17139454)
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?
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by busterarm on Wednesday May 23, 2018 @09:00PM (#17140020)
Microsoft, Android, Firefox, Electron and Chrome aren't currencies.

They have an underlying value/utility. People have a real, tangible need _outside of the use of those products_ to get them fixed. Can you say the same for a cryptocurrency?

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by Jommi on Wednesday May 23, 2018 @10:47PM (#17140645)
yes?
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by Ygg2 on Wednesday May 23, 2018 @11:19PM (#17140822)
What is the value of currency you can legally print on any printer?

Zero.

Edit: any crypto-currency you can exploit gives you option to print yourself money.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by erikpukinskis on Thursday May 24, 2018 @01:53AM (#17141423)
Double spend isn’t like printing money on a printer.

It’s more like being able to write two checks for your whole bank balance and having them both clear.

So very relevant are:

- whatever goods you bought with the checks need to be impossible to recall. So, like you need to find (two) someone’s who will effectively cash your check. You can’t buy a house because the police will come take the house back.

- you need to do it fast. The second you make are the first transaction you need fork and start mining hard. 51% gives you a speed advantage, but it’s very small. It still takes time to get the network to follow you.

Double spend is a very specific heist. Even if someone did it, it wouldn’t mean Bitcoin is valueless, it would just mean a certain class of heist is somewhat more probably and people need to adjust their security practices accordingly.

Tricks like waiting for extra confirmations, requiring identification before accepting payment, etc, are easy remediations.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by Jommi on Wednesday May 23, 2018 @11:46PM (#17140932)
You're over reducing things to the point where they don't make sense anymore lol

First of all, the value of a currency that could be printer on any printer might not actually be even 0.

Secondly, cryptocurrencies do not operate in vacuum. Its not as simple as "printing yourself money".

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by Ygg2 on Thursday May 24, 2018 @01:14AM (#17141267)
Right, it could possibly be negative.

Second, if I went to a store spent 199 dollars and those 199 dollars magically reappeared in my hand, didn't I create money out of nothing and reduce dollar value? Yes I did. Even if I never cloned any money I reduce the expectations of future stores that their money won't magically disappear.

And yes, I am aware banks do this, but they are regulated and when they abuse it, you get a financial crisis.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by alttab on Wednesday May 23, 2018 @07:51PM (#17139583)
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 M... by doorbumper on Wednesday May 23, 2018 @08:02PM (#17139653)
Bitcoin hasn't been useful as a currency for a long time. I don't think that's a good measure for determining how an event might affect bitcoin price.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by hapnin on Wednesday May 23, 2018 @11:58PM (#17140979)
Bitcoin averages something on the order of 200,000 transactions per day. It's useful to someone.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by wpietri on Thursday May 24, 2018 @12:53AM (#17141186)
That's definitely not proof of real economic utility. How many bets happen in Las Vegas every day? But economically, they're negative-sum events exploiting cognitive weaknesses.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by conanbatt on Thursday May 24, 2018 @01:51AM (#17141413)
They are not negative sum, because they provide entertainment.

Also, all systems that pay taxes are negative sum as well! Utility is not measured in money.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by dpq on Thursday May 24, 2018 @07:04AM (#17142840)
Entertainment can also have negative value. That's what the parent meant: your entertainment is provided by someone exploiting your gambling-addicted (and gambling may cause an actual addiction afaik, no less so than opioid addiction although based on different biochemistry) dopamine circuitry in order to extract actual (social) value.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by conanbatt on Thursday May 24, 2018 @11:58AM (#17145247)
All entertainment is someone exploiting your chemistry. Thats the whole point.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by wpietri on Thursday May 24, 2018 @11:06AM (#17144698)
They mainly provide addiction. Go to a casino sometime and look around. Do those people look like they're entertained? The slot machine zombies barely look human anymore.

You're also wrong about taxes. Consider my local taqueria. They buy raw materials and create value by making ready-to-eat food just when people are hungry. They receive cash in exchange, a portion of which they pay in taxes to fund the infrastructure their business depends upon.

That is positive sum for all participants. It has to be. If taxes tipped it into the negative sum category, they'd eventually close down.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by conanbatt on Thursday May 24, 2018 @12:03PM (#17145298)
I dont think you've followed through on that model of yours.

If you buy 50 dollars of taco materials, then taco materials seller makes likes than 50 dollars ,because the state will charge a tax on him. If he didnt sell 50 dollars worth of raw materials, he would have 50 dollars of raw materials to consume, instead of less than 50 dollars.

On the other side, making the taco, you have the same issue: if you sell 100 dollars of tacos, and someone pays you 100 dollars for them, you then pay taxes.

You earn less than 100 dollars, and someone else lost 100 dollars. Repeat the proces ad-infinitum and your holdings go to 0. (assuming for simplification, any rate of positive taxation on income).

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by wpietri on Thursday May 24, 2018 @02:27PM (#17146860)
This makes no sense at all, and is not how business works.

Most economic activity is positive sum. When I'm hungry and on the go, a taco is more valuable to me than raw taco materials, so I pay more for it. Value has been created. The taqueria owner takes money in, pays their expenses, and is left with a profit. Taxes are paid out of that profit, and you could just as well model it as another kind of expense, a societal infrastructure fee.

Many countries use value creation as an explicit taxation model: https://en.wikipedia.org/wiki/Value-added_tax

Those are still positive-sum interactions in the economic sense: https://www.tutor2u.net/economics/blog/qa-what-is-a-positive...

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by conanbatt on Thursday May 24, 2018 @08:34PM (#17149725)
> Value has been created

But not dollars, which is what you are using to classify gambling as negative-sum.

> Many countries use value creation as an explicit taxation model: https://en.wikipedia.org/wiki/Value-added_tax

If the gobernment collected that tax but didnt spend or issued money, even VAT ends up capturing all the money supply.

This is an unnecessary long argumentation. Gambling is not negative sum because they provider entertainment that has utility.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by wpietri on Friday May 25, 2018 @02:58PM (#17156847)
That is not in fact what I am using to classify gambling as negative-sum. It is also negative-sum in cash terms, but I'm speaking of value.

I understand you are claiming the entertainment value outweighs the harm of exploitation and addiction. I strongly disagree.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by conanbatt on Thursday May 24, 2018 @12:02PM (#17145293)
I dont think you've followed through on that model of yours.

If you buy 50 dollars of taco materials, then taco materials seller makes likes than 50 dollars ,because the state will charge a tax on him. If he didnt sell 50 dollars worth of raw materials, he would have 50 dollars of raw materials to consume, instead of less than 50 dollars.

On the other side, making the taco, you have the same issue: if you sell 100 dollars of tacos, and someone pays you 100 dollars for them, you then pay taxes.

You earn less than 100 dollars, and someone else lost 100 dollars. Repeat the proces ad-infinitum and your holdings go to 0.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by JackFr on Thursday May 24, 2018 @08:02AM (#17143128)
Not (necessarily) true.

Expected value is not the only thing to consider. Higher moments matter.

Insurance typically has negative expected value but it’s rational to buy it (in conjunction with owning the insured object) to reduce one’s variance.

Gambling will increase the variance of one’s portfolio at the cost of expected value, which can be rational depending on one’s situation.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by notahacker on Thursday May 24, 2018 @11:08AM (#17144717)
An awful lot of casino gambling involves series of small stakes bets on low payout options which don't even meaningfully increase upside portfolio variance over time after the house edge has been taken out. Might still be rational from a utilitarian perspective if one really, really enjoys card games of course, but not from a portfolio allocation perspective.

Apart from weird edge cases where an actor needs to double their money overnight to return to solvency in order to have a chance of benefiting from an income stream in future, there aren't many cases where it makes sense from a portfolio allocation basis given the existence of non-negative expectation bets in other markets with a wide range of possible variances. The insurance and investment management industries are built on the principle that economic rationality works in exactly the opposite way to gambling: that inherent value exists in reducing risk.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by wpietri on Thursday May 24, 2018 @11:10AM (#17144746)
Exactly. Thank you.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by hapnin on Thursday May 24, 2018 @01:44AM (#17141388)
Use as a currency was the point I was addressing. Bitcoin has been a working network for 9 years with 300,000,000 plus transactions.

It's a useful currency.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by simias on Thursday May 24, 2018 @05:04AM (#17142287)
300 million transactions in 9 years is ridiculously low compared to any "fiat" currency. Googling around I find a post that gives a lower bound for number of debit card transactions in the USA alone as 47 billions for 2012 alone[1]. That's not counting the rest of the world and the other exchange media like cash or bank transfers. 300 million transactions is nothing. I mean thing about it, it's one single transaction for every person in the USA over the course of 9 years. Alternatively it's less one transaction per year for the entire population of Canada.

Amazon alone probably handles more transactions over the course of a couple of weeks.

[1] https://www.quora.com/How-many-credit-and-debit-card-transac...

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by wpietri on Thursday May 24, 2018 @11:03AM (#17144663)
Gambling has way more transactions. LIBOR options have more transactions. Any actively traded stock has more transactions. None of those things are currency.

Even prominent Bitcoin advocates agree it's not effective as a currency: http://avc.com/2017/08/store-of-value-vs-payment-system/

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by Frondo on Thursday May 24, 2018 @09:16AM (#17143645)
I wonder how many minutes it'd take for cash to manage 300 million transactions.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by baq on Thursday May 24, 2018 @05:57AM (#17142532)
Visa does 2000 per second. 200k per day is almost laughable.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by sudomake on Thursday May 24, 2018 @09:22AM (#17143701)
And Visa can do 7x that in a minute
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by robertAngst on Wednesday May 23, 2018 @10:11PM (#17140465)
speak for yourself, only thing I cant pay is my mortgage.

I have a shift card, bought tacobell with bitcoin.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by jjeaff on Wednesday May 23, 2018 @10:29PM (#17140547)
That's not buying anything with Bitcoin. You are converting your Bitcoin to USD and then purchasing using the traditional, centrally controlled financial system.

And that's not even considering the transactions fees it costs to get the Bitcoin to your account.

Then there are the transaction fees for using the card, which coinbase says is free "for now".

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by brownbat on Wednesday May 23, 2018 @11:52PM (#17140955)
That's like saying you can't buy anything with a VISA.

Sure, transactions are intermediated through some consensus denomination for exchange. So?

He still lost bitcoin and gained tacos. Just as someone else might lose a portion of a credit balance and gain tacos. You get just as full either way.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by beefield on Thursday May 24, 2018 @02:02AM (#17141452)
No. Someone is traveling to Europe, going to a restaurant and paying for the Euro nominated beer with his US based VISA and starting to claim that hey, cool, I paid for the beer with USD. You see, I lost a portion of my USD balance and gained a beer.

If you insist that the guy paid his beer with USD, it is going to be very difficult to discuss about anything as the meanings of the concepts are so twisted.

It is quite obvious that using a credit card that then accepts BTCfrom you does not mean that you use BTC to pay for anything but your credit card bill.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by wpietri on Thursday May 24, 2018 @12:57AM (#17141204)
It's more like saying you can't buy anything with gold.

Credit and debit cards are just a way of shifting dollars around. Bitcoin is more a commodity than a currency. Yes, you can convert gold or oil to dollars and buy things, but you can't walk into a store and give them some gold flake or a quart of Texas crude in exchange for a candy bar.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by brownbat on Thursday May 24, 2018 @04:51AM (#17142241)
> Credit and debit cards are just a way of shifting dollars around

A credit card is shifting a line of credit, an intangible promise to pay, a form of trust, that happens to be denominated in dollars.

We can pretend it's just a balance of dollars, even though it technically isn't, because it makes conversations easier, and in practical fact that's how it appears to work. But that's just a shorthand.

We can use the same shorthand to say someone bought something with bitcoin.

There's no reason to demand perfect technical precision with bitcoin and no similar pedantic precision with lines of credit.

> you can't walk into a store and give them some gold flake or a quart of Texas crude in exchange for a candy bar

I think this is the best test. Here the guy has done that. He walked in with bitcoin and walked out with tacos. When you say that's not really what happened, it feels like a no true scotsman response.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by wpietri on Thursday May 24, 2018 @11:00AM (#17144631)
It did not. He gave them dollars, not a quart of crude. That he might have a side deal with somebody else to trade beanie babies for dollars does not make beanie babies a currency.

Bitcoin is not a currency. Plenty of other things are true currencies, so there's no fallacy here.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by nicky0 on Thursday May 24, 2018 @02:37AM (#17141564)
Was there an individual bitcoin transaction for each purchase? No, he just paid his credit card bill with bitcoin.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by lagadu on Thursday May 24, 2018 @08:30AM (#17143275)
Whatever the receipt says is what you paid with; those receipts are definitely in USD.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by kjhnwasdkn on Thursday May 24, 2018 @04:02AM (#17142003)
Sure you could also pay your groceries with lead dispensed from a gun. But that's currently nowhere near broad addoption. It just doesn't meet the definition of "currency", though it will virtually always be current.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by tromp on Thursday May 24, 2018 @04:40AM (#17142201)
You didn't buy tacobell with bitcoin unless Taco Bell quoted you a price in BTC...
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by IncRnd on Wednesday May 23, 2018 @10:34PM (#17140570)
Shift isn't sustainable in it's current form. They are temporarily not charging for domestic transactions. Since there is a cost for those transactions, there will eventually be a fee per transaction.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by EpicEng on Wednesday May 23, 2018 @08:03PM (#17139656)
This has already happened multiple times to BTC and it's still around. BTC is not a currency; that train left long ago.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by robertAngst on Wednesday May 23, 2018 @10:10PM (#17140460)
I dont think it has?
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by IncRnd on Wednesday May 23, 2018 @10:29PM (#17140549)
You don't think what has? There have been double spend attacks against BTC.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by Jommi on Wednesday May 23, 2018 @10:47PM (#17140648)
source?
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by zeven7 on Thursday May 24, 2018 @01:19AM (#17141296)
Not exactly a double spend, but billions BTC being printed out of thin air: https://bitcointalk.org/index.php?topic=822.0
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by celticninja on Thursday May 24, 2018 @07:57AM (#17143105)
It has happened before but that was in 2010 when the codebase was < 2 years old.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by IncRnd on Thursday May 24, 2018 @11:31AM (#17144976)
It's happened quite a few times after that. Consider the merchants who have been known to use fewer than the standard # of confirmations and what it takes to reverse or reuse those charges. For example, here is a blog post on one way to do this: https://blog.acolyer.org/2015/10/01/misbehavior-in-bitcoin-a.... If you want to search you will find that there are scripts to automate this type of action by constructing bitcoin transactions.

Also, consider ghash.io or the odd OKPAY double spends.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by vntok on Wednesday May 23, 2018 @07:56PM (#17139618)
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 M... by djsumdog on Wednesday May 23, 2018 @11:20PM (#17140826)
Credit Card companies and banks can reverse the transactions, so long as they keep track of things in batches, have strong backup system for their ledgers. So long as they're not SWIFT transactions that leave the country, and the country that's attacked as a strong/regulated inter-bank transfer system.

If a bank is critically hit so bad funds become impossible to correctly attribute to people (Fight Club type unrealistic scenario), at least in the US FDIC would probably come in to play. The bank might even have to be treated as a failed bank.

People wouldn't stop using banks, but they would stop using that bank.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by eric-hu on Thursday May 24, 2018 @08:57AM (#17143482)
> People wouldn't stop using banks, but they would stop using that bank.

I'd really like to live in a world where that's true, but I don't see Equifax going anywhere. PayPal does a form of this as well, except it's the central system and not a rogue actor that locks your money away. Well informed users avoid PayPal, but there appear to be many more uninformed users.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by XorNot on Thursday May 24, 2018 @12:58AM (#17141207)
Neither of those things "are money" and they're all highly reversible.

A major hack against Visa would absolutely tank the value of Visa the company however, and if people who believed they were paid weren't made whole somehow then it would also tank the acceptance of Visa.

And it would be an ongoing devaluation without Visa being able to show they'd fixed the underlying flaw - which you can't with a 51% attack.

Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by user9182031 on Thursday May 24, 2018 @08:44AM (#17143376)
My credit card gets stolen yearly. Sure, they can reverse the charges but changing the number everywhere is annoying..
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by bdonlan on Wednesday May 23, 2018 @08:44PM (#17139924)
Don't underestimate how long it takes to deploy a fix to such a vulnerability. Any change in consensus (which this would be) is a hard fork, and deploying it without carefully coordinating months in advance is certain to cause chaos.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by oh_sigh on Wednesday May 23, 2018 @09:42PM (#17140291)
Why do you think a double-spend attack would be easy to figure out? It could rely on start of the art crypto attacks which aren't known to the general public, or some very obscure bug which has slipped past thousands of eyeballs.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by XR0CSWV3h3kZWg on Wednesday May 23, 2018 @07:34PM (#17139457)
You won't really be able to process tx that low, you'll need to pay a tx fee proprtionate to the number of bytes. 1 satoshi per byte is a good rule of thumb for a very cheap tx. It takes more than 1 byte to describe one satoshi, so you can't get your tx to propagate.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by oh_sigh on Wednesday May 23, 2018 @08:00PM (#17139639)
Theoretically the attacker could also be picking up 0-fee transactions, but my intent was to really say this: it doesn't matter how small a double spend is - the ramifications for the network are the same.
Re:Bitcoin Gold Hit by Double Spend Attack, Exchanges Lose M... by jpttsn on Thursday May 24, 2018 @03:54AM (#17141956)
Would even a single counterfeiter be enough to destroy a new fiat currency, or is your thesis specific to crypto?