How to do Double spend | Bitcointalksearch.org

bob123

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There are multiple approaches to double spend a transaction.

Relay the original TX to the victim while relaying the double-spending TX to the rest of the network
Start a race attack by 'separating' the network
Cooperate with a miner
RBF

But based on your actual knowledge regarding bitcoin, i heavily doubt that it is for 'educational purpose'.

Fortunately you won't be able to make use of it outside of a testing environment.

Quote from: nc50lc on August 04, 2019, 09:11:55 PM

If ever there are two transactions that are trying to spend the same UTXO was accepted by a mining node, one of them will eventually get a confirmation and one will be discarded.
The only exception is: if both of them have too little fee to get a confirmation within (default) two-weeks time, both will be rejected.

Just because they will be dropped from the mempool, this doesn't mean that it got rejected.
Actually, only one transaction should (if following the protocol specification) be allowed to enter the mempool. The first one. The second one should get rejected.

nc50lc

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Quote from: figmentofmyass on August 03, 2019, 06:12:51 PM

Quote from: Khaos77 on August 03, 2019, 11:17:17 AM

Funny, how many of the same users tout how bitcoin is so secure, but are skittish of explaining how to doublespend on BTC.

Option 1:
1st , you have to find someone dumb enough to accept zero confirmations

bitcoin's entire security model against double spending depends on mining confirmations. only a total noob (or someone malicious) would tout zero-confirmation transactions as secure.

The main issue on his post is most nodes will reject the second unconfirmed transaction due to the second attempt to spend the first TX's UTXO.
Nodes are designed to reject those by default and there's a very high chance that it will not reach a miner's node.

...unless it's labeled: RBF which is disabled by default <-(I haven't tested yet).

Quote from: BitcoinPanther on August 03, 2019, 11:35:04 AM

I believe by principle, if you try that, the double-spending attempt will be considered both canceled transactions.

If ever there are two transactions that are trying to spend the same UTXO was accepted by a mining node, one of them will eventually get a confirmation and one will be discarded.
The only exception is: if both of them have too little fee to get a confirmation within (default) two-weeks time, both will be rejected.

kaya11

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Quote from: crwth on August 03, 2019, 04:07:28 AM

I like how you say, "educational purposes"

Why not search it in Google and use the researches that are there in your results? I think it's easy to do that but I hope you share what you are planning to do or put out the "educational purpose" you are talking about. Lol.

Maybe he can't understand it just by reading, sometimes people needs live demo to understand it very well, including me, as he said he needs a live demo above. This guy is taking up our time.

Khaos77

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Quote from: figmentofmyass on August 03, 2019, 06:12:51 PM

Quote from: Khaos77 on August 03, 2019, 11:17:17 AM

Funny, how many of the same users tout how bitcoin is so secure, but are skittish of explaining how to doublespend on BTC.

Option 1:
1st , you have to find someone dumb enough to accept zero confirmations

bitcoin's entire security model against double spending depends on mining confirmations. only a total noob (or someone malicious) would tout zero-confirmation transactions as secure.

Quote from: Khaos77 on August 03, 2019, 11:17:17 AM

Option 2:
Coerce the 4 top bitcoin pool operators

how would you pull that one off?

If you don't know that , the second I said [coerce],
You're too naive and would be too traumatized if I went into detail.

figmentofmyass

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Quote from: Khaos77 on August 03, 2019, 11:17:17 AM

Funny, how many of the same users tout how bitcoin is so secure, but are skittish of explaining how to doublespend on BTC.

Option 1:
1st , you have to find someone dumb enough to accept zero confirmations

bitcoin's entire security model against double spending depends on mining confirmations. only a total noob (or someone malicious) would tout zero-confirmation transactions as secure.

Quote from: Khaos77 on August 03, 2019, 11:17:17 AM

Option 2:
Coerce the 4 top bitcoin pool operators

how would you pull that one off?

BitHodler

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Quote from: bitbunnny on August 03, 2019, 02:09:57 PM

Well, I don't think that he would actually succeed to make it in practice, I don't believe double spend is actually possible. And even if he did, that wouldn't have such deep impact like you describe, loss of confidence, price drop and everything. This is a little bit exaggerated.

Double spending is quite easy if you know how to do it. I have done it once (before RBF was a thing) in order to actually have the coins I sent to my exchange account confirm, which otherwise might have taken a day or so.

Scammers have double spent on ATMs and noobs they "sell" Bitcoin to. Noobs see the Bitcoin show up in their wallet and think it's all right, not knowing that they don't have these coins until the transaction confirms.

And yes, this is actually a pretty common occurrence. It doesn't require you to "break" the network and therefore no one will panic sell. Safest option is to always wait for that 1 confirmation when transacting with someone you never met.

bitbunnny

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Quote from: Kakmakr on August 03, 2019, 01:31:03 PM

Now that you have a basic understanding of a double spend, you should consider the consequences of such an attack. Let's say you successfully execute a double spend, it would quickly get noticed and people will hear about this. The direct result of that would be that massive amounts of people will start dumping their coins, because the whole concept of "security" would be destroyed.

The demand for coins will dissapear and there will be a over supply of coins on exchanges .....the next thing you know, the price will go down to almost $0. So the attacker will never be able to do this again and the remaining coins they have will be worthless.

Never kill the Cow for it's meat, because you will lose the daily milk. Wink

Well, I don't think that he would actually succeed to make it in practice, I don't believe double spend is actually possible. And even if he did, that wouldn't have such deep impact like you describe, loss of confidence, price drop and everything. This is a little bit exaggerated.

Kakmakr

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Now that you have a basic understanding of a double spend, you should consider the consequences of such an attack. Let's say you successfully execute a double spend, it would quickly get noticed and people will hear about this. The direct result of that would be that massive amounts of people will start dumping their coins, because the whole concept of "security" would be destroyed.

The demand for coins will dissapear and there will be a over supply of coins on exchanges .....the next thing you know, the price will go down to almost $0. So the attacker will never be able to do this again and the remaining coins they have will be worthless.

Never kill the Cow for it's meat, because you will lose the daily milk. Wink

YuginKadoya

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Quote from: sarmrakib on August 03, 2019, 12:10:59 PM

You didn't make it clear what really you wanna know .I think you wanted to know how to double btc or something else .However its really hard to double any investment but it is realty possible into crypto .But you need to have vast knowledge behind that .You can make it by trading ,gambling .But it always so risky to make profit in quick .So i wanna suggest to study on crypto you can make double your capital easily.

I really think it is not to double his BTC but to make a transaction and to transact it back to the same wallet again If my understanding was right, And I guess this is a newbie question and honestly didn't know a thing about how a bitcoin transaction works, And he then added that his friend doesn't want to teach him about it and that is why he is trying his luck asking here in the forum and asking is we can provide him with some example and clips he can watch, Well, we can not blame him about it and he is just asking nicely in my opinion but the thing is engaging with Bitcoin you will need to have basic knowledge about it first.

sarmrakib

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You didn't make it clear what really you wanna know .I think you wanted to know how to double btc or something else .However its really hard to double any investment but it is realty possible into crypto .But you need to have vast knowledge behind that .You can make it by trading ,gambling .But it always so risky to make profit in quick .So i wanna suggest to study on crypto you can make double your capital easily.

BitcoinPanther

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Double-spending is spending the same currency or token for two or more transactions.
It is like cheating since you have one single amount but you want to spend it for two or more transactions since the transactions need to be confirmed first before it will be considered as a successful transaction.

I don't think it is possible in Bitcoin. Bitcoin and Blockchain Technology were invented to prevent double-spending of digital currency. That is how Satoshi Nakamoto solved the problem of double-spending which is one of the factors of the financial crisis during 2008.

I believe by principle, if you try that, the double-spending attempt will be considered both canceled transactions.

Khaos77

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Quote from: ariellee on August 02, 2019, 07:35:10 PM

Hi, is anybody there who can please explain me how to do double spend ?
I heard that is was possible to make it on coinb.in but I don’t really know it works. I am only asking it for an educational purpose. Please please please
If my post is in the wrong section please tell me.
Thank you

Funny, how many of the same users tout how bitcoin is so secure, but are skittish of explaining how to doublespend on BTC.

Educational Purpose Only
Option 1:
1st , you have to find someone dumb enough to accept zero confirmations

then send the agreed upon amount of bitcoins, with either zero or almost zero transaction fee
get product or service and leave

then send the entire amount of that wallet to another address, with an extremely high transaction fee.

The Miners will process your transaction with the highest fee before the no fee , thereby negating the 1st transaction and helping you to double spend.

* Now all any receivers of bitcoins have to do to stop this from happening is wait the required # of confirmations, and it protects them from the above doublespend attack.* * Recommended to wait at least 3 confirmations.*

* Note: Some ALTS process transactions in the order received and do so at fixed fees, so the above attack would fail against them.*

Option 2:
Coerce the 4 top bitcoin pool operators into colluding to orphan 3 blocks excluding your 1st transaction
and replace it with one sending to another address you own.
This one , their is no protection for or defense against if you use bitcoin.

* This is the reason that many PoS coins are more secure than bitcoin,
but next you are going to hear people tout hashrate and energy waste like they actually matter in securing bitcoin,
but the truth is 4 pool operators are given over 51% control on a daily basis, corrupt them and the bitcoin network is your doublespend playground.*

Cool

Johnzky

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Quote from: TimeBits on August 02, 2019, 08:41:12 PM

Quote from: ariellee on August 02, 2019, 07:35:10 PM

Hi, is anybody there who can please explain me how to do double spend ?
I heard that is was possible to make it on coinb.in but I don’t really know it works. I am only asking it for an educational purpose. Please please please
If my post is in the wrong section please tell me.
Thank you

You don`t double spend.

If you want to double spend, the first thing you do is find the tallest building, now jump off it!

No You made me laugh on that mate 😂😂😂

Just like the comment above there is a possibilities that double spend can be use to mislead or to scam others,so basically this thing must not exist because there’s nothing this can bring good for crypto but abuse of knowledge and possibly scamming

crwth

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Quote from: Dreamchaser21 on August 03, 2019, 04:21:59 AM

If you want to know something, its true that its easy to search regarding on that topic so google is the best option I believe. Well, i never tried to do this such risky move and maybe OP is just asking for some experiences here. I might also interested to hear more about this, I don't know if this is working well so maybe anyone can share their experience and thoughts.

That is why Google became a verb. From what I have learned ever since I came to this forum, I know that it is not possible because of the blockchain and miners verifying each block. That’s why it has become a solid digital currency because “double spending” can’t be done. At least, that’s what i know from learning here. Or I may have missed something?

Dreamchaser21

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Quote from: crwth on August 03, 2019, 04:07:28 AM

I like how you say, "educational purposes"

Why not search it in Google and use the researches that are there in your results? I think it's easy to do that but I hope you share what you are planning to do or put out the "educational purpose" you are talking about. Lol.

If you want to know something, its true that its easy to search regarding on that topic so google is the best option I believe. Well, i never tried to do this such risky move and maybe OP is just asking for some experiences here. I might also interested to hear more about this, I don't know if this is working well so maybe anyone can share their experience and thoughts.

crwth

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I like how you say, "educational purposes"

Why not search it in Google and use the researches that are there in your results? I think it's easy to do that but I hope you share what you are planning to do or put out the "educational purpose" you are talking about. Lol.

Sonu_titu

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There are threads on Bitcointalk already explaining the complete double spend check this out:
https://bitcointalksearch.org/topic/m.50889936

In the above thread @Bitcoin_Arena, @o_e_l_e_o and few more have explained enough on this topic. Hope it will help you understand.

Thirdspace

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"true" double spending is not possible
but if a transaction hasn't received any confirmation, you can try to double spend (redirect) it
check this Open Source Automatic Double-Spending tool - Recover your stuck transaction
that is a thread of such tool and it's a fork of coinb.in, use it at your own risk!
after you understand how it works, I advise you to do this manually and offline using coinb.in

tsaroz

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Almost all people and most of the sites requires you to have a number of confirmations before making your deal done.
Even the sites that advertise zero confirmation deposit require you confirmations before withdrawing.

The easiest way to double spend is to load your private key in multiple wallet and send to different address before any of them confirms.

UserU

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It's like asking how to clone money.

Both are unethical and dishonest.

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