Questions tagged [doublespend]

This tag should be used for questions related to double spending. Double spends are when a money is spent more than one time. This is considered a form of fraud.

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120 views

Bitcoin Wallet: Will 2 payments within 10 minutes cause double spending

I'm using a bitcoin wallet for managing all my transactions. For example, If I have bitcoin 2, 3 and 5. Firstly, I buy a product with price 5. Bitcoin wallet will create a transaction from 2 and 3. ...
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1answer
999 views

Would a reduced block generation time make the Finney attack more difficult?

Related Question: What can be done to mitigate the risk of a Finney attack? The Finney attack is a form of double-spending attack where the attacker pre-mines a block containing a conflicting ...
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1answer
246 views

What if a pair of double-spent transactions are collected into a new block?

Let's say, Alice sent a bitcoin to Bob, and then immediately sent the same coin to another address controlled by her. A honest node collected these two transactions into a new block. Would the node ...
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3answers
5k views

Are there alternatives for proof of work?

Bitcoin uses proof of work to secure the network, Ripple uses a global consensus system and PPCoin uses proof of stake. Are there any known alternatives to the above methods?
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3answers
481 views

Will an attacker's forked branch of block chain be used in bitcoin confirmation?

From what I understand, transactions are agglomerated into a block, proof of work is done by computing a hash value for the block, then added to the block chain. When a block is added to the block ...
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1answer
97 views

Is Bitcoin the first e-cash scheme which solved the double-spend problem?

Is Bitcoin the first trustless e-cash scheme which solved the double-spend problem? I'm under the impression it is and that was one if its greatest contributions, but I couldn't really find a source ...
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2answers
2k views

Could any standard fee transaction be double spent by using a higher fee?

I realize that if somebody makes a transaction without any fees and there have not yet been any confirmations, then the transaction could be double spent by just spending the same inputs to a ...
2
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1answer
258 views

double spending

I do understand the necessity for a proof of work to avoid malicious miners mining a fork on the current blockchain. This is difficult as this proof of work takes lots of power (and time). Yet I don'...
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0answers
42 views

Globally distributed accomplices for improved outcome in race attack

Would it help you to win a race attack if you had accomplices from all over the world, say Berlin, Beijing, Boston, and Buenos Aires all propagate your transaction to the nodes that they're connected ...
2
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1answer
63 views

What information about a transaction can be assumed accurate before confirmation?

When sending a Bitcoin transaction, what information in that transaction can be assumed to be accurate before receiving a confirmation? Can you verify the from address? Can you verify that the ...
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3answers
4k views

How do miners detect double-spending?

Assuming I spent 1BTC, then waited a few months and then spent it again. How is this detected? Do the miners go through the entire blockchain to assure the coin was never spent before?
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1answer
132 views

Detection of double spend in Bitcoin for aged transactions

This is just to verify my understanding of Bitcoin double spend detection. 1) Use of UTXO indexes : This ensures that there as been no spend from that output (transferred to recipient in Block of ...
2
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1answer
283 views

why is double-spend not an issue for payment channels?

Micropayment Channels (MPC) cannot be used currently because of transaction malleability, I hear. AFAIK, people saying that have in mind that the refund & payment tx, which have as input the ...
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3answers
95 views

What incentive is there for a miner to not cancel his own 'real' txs

It is said that a Bitcoin miner attacker with enough CPU power to outrun the entire network is better off mining honest bitcoins - which is not correct since by creating a false block chain the ...
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3answers
5k views

What is the best way to recover from an accidental double-spend?

Came across an issue where I was given the message: "Error: The transaction was rejected. This might happen if some of the coins in your wallet were already spent, such as if you used a copy of ...
5
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1answer
2k views

What to do about a “stuck” transaction?

I started the standard client with --rescan instead of -rescan after switching wallets and before synchronizing with the latest blockchain, and made an going transaction. This transaction got "stuck",...
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2answers
912 views

Double Spending before confirmation [duplicate]

What's to prevent someone from using bitcoin at a store like subway and double spending to buy the sandwich before a confirmation is made? Since subway obviously isn't going to wait for a ...
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1answer
109 views

How long should I wait to consider that the transation is “definitely” confirmed?

When one transaction is broadcasted, what is the probability that it won't be confirmed? (By probability, I mean the observed probability on the blockchain. If a person intentionally spend twice 1 ...
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2answers
2k views

When are multiple transactions spending the same output in the same block considered a double spend?

Here is an example of multiple transactions in the same block, all spending from the same output. I created these using the Electrum wallet, telling Electrum to spend a little bit of the BTC from the ...
2
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1answer
89 views

What makes an unconfirmed tx 'suspicious'? (likely to be replaced or never confirm)

When looking at Bitcoin unconfirmed transactions, I'm trying to distinguish between txs that are likely to confirm (whether that be in the first next block or in 2 hours) versus txs that are likely to ...
8
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1answer
69 views

Merchant tool that will dynamically adjust the # of required confirmations based on network hashrate data

Satoshi built Bitcoin to be a decentralized network. Some of the original recommendations (such as waiting for 6 confirmations) relied on statistics that related to level of decentralization. https://...
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1answer
88 views

How to pratically doublespend bitcoins?

I tried to put bitcoins into an p2p exchange with bitcoin-qt. I added a to small transaction fee, so the coins are now stuck as "Unconfirmed". The offer from the exchange is overdue, so all that will ...
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1answer
120 views

Restrict the Bitcoin usage only during a particular period

I would like to know if its possible to use a Bitcoin at present in the following scenario. When I send a Bitcoin to an another user,I set certain parameters on the Bitcoin, like it can only be used ...
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1answer
272 views

How many confirmations do bitcoin escrow websites wait on average?

To me it seems very dangerous not to wait for 6 confirmations when running an escrow. The scenario I'm thinking of: a miner deposits a large sum of bitcoins the escrow waits for one or two ...
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2answers
380 views

Blockchain for internet-of-things or is there any mining algorithm that can be utilized in low-computational power devices preserving security?

Recently IBM and Microsoft showed their interest (IBM post, Microsoft post) in utilization of blockchain for internet of things development. Let's assume that in close future the blockchain technique ...
3
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1answer
235 views

What happens if a miner confirms their own double spend?

Suppose an attacker makes a double-spend and controls the mining pool that happens to find the good which confirms the transactions. What happens? I suppose the network hopes that a vigilante sees ...
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2answers
2k views

Bitcoin without mining

Several months ago I've stumbled an interesting question about the Ripple system: How does Ripple solve the double-spend problem? Specifically about how double-spending is solved in Ripple. As you ...
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1answer
353 views

Can a malicious majority miner rewrite history?

Is it the case that a malicious miner with the majority of hash power (say, 99%) can perform a double-spending attack by rewriting history? If so, I can't understand how. If not, under what ...
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2answers
4k views

How does ShapeShift operate on 0-1 confirmations

ShapeShift can exchange user's crypto currency almost instantly. They state that most transactions don't require any confirmations: Small deposits are processed with zero confirmations. Larger ...
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1answer
373 views

Is it possible to use Selfish Mining to steal bitcoins?

Is it possible to use the Selfish Mining algorithm to steal bitcoins?
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3answers
457 views

How is over-spending one block apart prevented?

So, let's say you have a wallet with 20BTC, and you have a flow like so: You send 15BTC to A in block 1 You send 15BTC to B in block 2 What happens if at block 1 there are two chains across miners. ...
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5answers
6k views

Has there ever been a successful double spend attack on the Bitcoin network? If not, is it really necessary to wait for confirmations?

There is a lot of concern about waiting for confirmations to avoid a double spend attack, but has there ever actually been a double spend attack? It seems to be that there are two types of double ...
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1answer
171 views

How to track and handle double-spend attacks?

If a double-spend attack is pulled off, how to manually verify transactions via the bitcoin daemon and how to know how much amount lost? Will the saved transaction hash be re-usable to obtain info ...
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2answers
146 views

Paranoid Merchants on double spending [closed]

How can merchants be alerted of Double-spending attacks? Let us take a hypothetical case where a merchant offer a BTC deposit wallet to his users, User deposits Bitcoins and it's credited to his ...
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1answer
170 views

Details in double spend detection [duplicate]

I'm confused with the details in double spend detection. my question is if Alice first sends her 10 BTC to Bob, and then sends the same 10 BTC to an address that belongs to herself. How do Bitcoin ...
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1answer
166 views

Why can't a transaction be redirected after it is signed? [duplicate]

Scenario: Step 1: User-1 initiates the TXN-1 to pay to User-2 and the TXN is not yet confirmed with the ongoing block POW. Step 2: What prevents fraudster (anyone a miner or someone listening/...
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1answer
1k views

What is the risk of waiting for just one confirmation to validate a transaction, assuming the counterparty is not a miner?

I am trying to determine how many confirmations would be reasonably safe to wait before accepting a Bitcoin transaction from an attacker that is not a miner and hence cannot rely on Finney attacks, ...
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3answers
14k views

How many confirmation do i have to wait before i can spend the inputs I already received?

Can I spend Inputs with 0 confirmations?? If I could, are there some restrictions?
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1answer
218 views

Bitcoins stuck - No double spend possible

I have a problem with my address 1Dss5sKJDZ1Kkhh3KRyoekeZpC4S1WehD. As you can see, I transferred money to the same address by mistake - without any fee. The transaction ...
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1answer
124 views

What are the chances of someone coming up with a new and simple/out-of-the-box solution for the double-spending problem?

The proof-of-work solution is simple but has many drawbacks (waste of time, energy and uncertainties about its security in the future). The consensus solutions proposed by Ripple/Stellar are too ...
3
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1answer
245 views

Why it is not possible for a payee to verify double-spends of the coin?

I'm reading Bitcoin paper of Satoshi Nakamoto (https://bitcoin.org/bitcoin.pdf). It says: Each owner transfers the coin to the next by digitally signing a hash of the previous transaction and ...
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1answer
151 views

How do I detect a double-spend in real-time, like Bitpay?

By Bitpay to pay only take 10 seconds to complete. How do they do it?
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1answer
232 views

What would you do while a hard fork lasts?

It is conceivable (though generally buried with cognitive dissonance, I imagine) that a hard fork might not get resolved. This almost happened once before, and the miners picked the fork that solved ...
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2answers
608 views

Where is coinbase transaction after a hacker successfully performs >50% attack?

Here is the scenario: Honest nodes build one block from Block_1. Hacker nodes privately build four blocks from Block_1 and broadcast these malicious blocks. Now, where is the honest node's ...
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2answers
647 views

What can a dishonest node do (or try to do)?

Except this kind of attacks: https://en.bitcoin.it/wiki/Double-spending For example can he simply create a new block that includes some invented transactions that steal money from real address? ...
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1answer
125 views

Can a double spend attack be obfuscated by mimicking the transactions seen before the fork?

An attacker controls the majority of the hashing power and wants to double spend without arousing suspicion. If they mirror the public chain's activity while generating the private fork and the fork ...
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3answers
691 views

Why doesn't bitcoin place additional constraints on competing block chain forks, other than length of chain? (e.g., time and confirmation count)

In Bitcoin's proof-of-work system, consensus on which chain of blocks should be considered the "true" block chain is based only(?) on which chain is longer. Accordingly, to quote a nicely written ...
7
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1answer
772 views

Speeding up confirmation by double-spending a transaction stuck in mempool

In the context of no-fee transactions that can take a long time to get their first confirmation, is it possible to use raw transactions and double-spend the original transaction by broadcasting ...
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1answer
114 views

How would this double spend attack be prevented?

I know, that a user cannot create a fork in the chain. Also, it is said, that since every transaction is publicly announced, any attempt of double-spend on the same chain would be rejected as the ...
7
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2answers
651 views

Possible to create a double spend attack by replacing a Tx in the merkle tree?

This question on crypto.SE describes how preimage attacks are avoided in the Bitcoin network. For a second preimage attack: hash(x) = hash(y) implies hash(hash(x)) = hash(hash(y)) So it ...