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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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25
votes
3answers
36k views

What is a double spend?

What is a double spend? As someone who uses Bitcoin, what do I need to know about how the Bitcoin system prevents double spends? Are there still circumstances where they can occur?
32
votes
2answers
13k views

What is a Finney attack?

What is a Finney attack? Extra points for explaining its purpose, the prerequisites for it to be possible, how the attack can be performed and the origin of the name "Finney attack".
54
votes
7answers
44k views

Can bitcoins be counterfeited?

Traditional currencies have anti-counterfeiting features designed to make them hard to copy, but despite this attempt counterfeit money is a real threat. Since bitcoins are digital, it's trivial to ...
40
votes
2answers
5k views

How does Ripple solve the double-spend problem?

How does the Ripple system solve the double-spend problem? Does it also use some block-chain-like entity that officially dictates which transactions are confirmed and which are not, or does it use ...
15
votes
1answer
975 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 ...
16
votes
2answers
6k views

How do I detect a double-spend?

As a vendor, how do you detect a double-spend? I'm happy to tell end-users that I'm proceeding with a transaction on 0 confirms, simply assuming everything is fine. I'm selling physical goods and so I ...
28
votes
5answers
5k 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 ...
8
votes
3answers
4k 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 ...
21
votes
1answer
3k views

What does the Bitcoin client do when it receives conflicting transactions?

I've been assuming that the second transaction will simply be discarded as invalid, while the first waits at 0/unconfirmed until it actually gets into a block (requiring a "-rescan" or similar if the ...
5
votes
1answer
3k views

Understanding a Bitcoin Double Spending Transaction by Performing one on yourself

Everyone talks about preventing a double spend transaction, but how does one do one to yourself in order to better understand the steps involved by the attacker? What is required to do a double spend?...
2
votes
1answer
247 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'...
11
votes
2answers
586 views

In a double spend attempt, how is the valid transaction chosen?

Suppose I publish the private key of an address that contains 1 bitcoin. If two people try to transfer this bitcoin to another address before a new block is found, who gets it? How is this decision ...
9
votes
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 ...
3
votes
1answer
212 views

JSON-RPC to detect double-spent TXs

How can I be positive that one of the incoming payments to my bitcoin-core was double-spent after it was confirmed once by the network, through the JSON-RPC interface? Related questions: How do I ...
2
votes
1answer
204 views

Is there a risk of double-spending when making a face-to-face transaction?

When exchanging funds or services face-to-face, is there a risk of a double-spending attack? If there is, how could it be technically done?
22
votes
2answers
5k views

What are the pros and cons of Ripple's consensus as compared with Bitcoin's proof-of-work?

One of the major differences between Bitcoin and Ripple is how they process transactions. I can think of three ways in which Ripple's "consensus" scheme is superior to Bitcoin's proof-of-work: Less ...
17
votes
3answers
4k 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?
6
votes
2answers
1k views

Double Spending - Does each node maintain a list of unspent transaction references?

My Understanding Of How Bitcoin Prevents Double Spending Each transaction contains references to the input transactions and ever node has to verify all transactions from time immemorial to ensure ...
3
votes
1answer
791 views

How does SPV prevent double spending of UTXO?

I am new to Bitcoins. I have read about how double spending is prevented in Bitcoins. Suppose A, a peer, receives 'B' BTCs from various transactions: B1,B2,B3, etc. Also, A had spent 'S' BTCs in ...
8
votes
4answers
948 views

How do people actually try double-spends?

I've occasionally seen people online claiming they were victims of a double-spend because they handed over something of value in exchange for a bitcoin payment with no confirmations. Although I ...
11
votes
2answers
1k views

Double spend attack by sending higher fee transaction directly to the pools possible?

The standard client prioritizes TXs by the time of receipt, e.g. a conflicting transaction will not be relayed. This is not enforced by the network, though. Is there anything that would prevent this ...
11
votes
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 ...
7
votes
1answer
613 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 ...
2
votes
2answers
174 views

How confirm my own doublespend transaction got confirmed

Transactions in the testnet are right now almost always double spent with a new txid (possible due to tx malleability). This is actually quite nice for testing purposes. So I'm wondering - when I ...
13
votes
2answers
2k views

How to minimize risk when accepting zero confirmation payments?

I'm trying to setup a way of accepting Bitcoin payments in real life situations, where waiting for confirmations is typically not an option. I understand this is never 100% risk free (especially with ...
6
votes
2answers
7k views

How is a Transaction Output Marked as Spent?

The Bitcoin developer guide states that each output of a particular transaction can only be used as an input once in the block chain. Any subsequent reference is a forbidden double spend—an ...
14
votes
2answers
1k views

Does any pool accept higher-fee transactions of a double spend, instead of the earlier one?

Some pools use a modified bitcoind that uses different rules for choosing the transactions to include in a block. Are there any pools that knowing one transaction to be included in a block would ...
5
votes
2answers
606 views

How to perform a double spend attack in websites that accept transactions with 0 confirmations?

To perform a Finney attack or a 51% attack I need to have lots of computational power, but in this case (a website that accepts transactions with 0 confirmations) it seems to me that I only need to ...
3
votes
2answers
3k views

How does a double spend get resolved when two miners find conflicting blocks at the same time?

I was trying to learn about Bitcoin and its flow. Actually, I was stuck how the control flows in solving the double spend. For eg. if Ta and Tb are a double spend of the same transaction with ...
8
votes
3answers
756 views

Why is Poisson instead of Negative Binomial used for computing attacker's potential progress?

In chapter 11 of the Satoshi's paper it is claimed that: The recipient waits until the transaction has been added to a block and z blocks have been linked after it. He doesn't know the exact ...
3
votes
2answers
235 views

Single tx included in two different blocks

https://www.blockchain.com/btc/tx/a7bacce00e5df85d3547a3f83ac10c65eec30f715c1d77d8d4a7bc17fd470965 How is it possible that a single tx is included in two different blocks? Isn't it considered double ...
2
votes
1answer
332 views

Is it possible to use Selfish Mining to steal bitcoins?

Is it possible to use the Selfish Mining algorithm to steal bitcoins?
0
votes
2answers
392 views

How to recover from a double spending attack?

I found myself incapable of answering what would happen in this case, so here it is: A hacker (Mr Hacker) spends UTXO_1 and UTXO_2 in TX_1, depositing the monetary value of all TX_1's outputs into a ...
7
votes
7answers
2k views

Is performing a 51% attack / double spend on Bitcoin illegal?

Suppose I had an ultra large ASIC from the future, and could perform a double spend on the core Bitcoin network. At this point in Bitcoin's development, it is no longer a game - there's real money ...
5
votes
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",...
5
votes
2answers
234 views

Double spend transactions flag the node as “bad”?

I'm playing with raw transactions. It's easy to send two signed valid transactions at the same time from the same output to different addresses (making a double-spend attack). My doubt is: if I make ...
4
votes
2answers
3k views

Broadcast a signed transaction

I sent money from 4 inputs to 2 outputs, one of which I don't control. The transaction's fee is too small (didn't change my settings and the transaction fees got a lot higher, recently) and will not ...
3
votes
1answer
188 views

Which clients offer a way to replace unconfirmed transactions?

On this site, we see a lot of questions from people who have sent a transaction which isn't being confirmed, often because they have neglected to include an adequate fee. The Satoshi client doesn't ...
3
votes
2answers
257 views

Is something gained by double spending myself on a 51% attack?

I try to understand what consequences double spending may have. Let's assume I own 51% of the network and own three bitcoins wallets. If I double spend the coins from Wallet A to B and C - would I ...
3
votes
2answers
152 views

Why we need mining?

I know is related to these: What is the rationale behind Bitcoin mining? Why do we need Proof of Work in bitcoin? But I don't fully understand those answers, and I think usually is much easier to ...
3
votes
1answer
71 views

reproduce CVE-2018-17144 (inflation bug) on regtest for learning

I'm reviewing CVE-2018-17144 inflation vulnerability for learning. I think I reproduced the error on regtest. Is it a correct way to reproduce it? I want to know if I'm missing something about it. ...
2
votes
1answer
480 views

Is it possible to execute a double-spending attack in Ripple during a network split?

From the spec (emphasis added): Under a net split, a ledger may be closed by the minority of network, this ledger may be discarded in the future. Does this mean it would be possible to spend twice,...
2
votes
3answers
1k views

What's the easiest way to someone to double-spend 0-confirmation transactions?

I heard there is a desktop app today that 'easily double spends 0-conf tx'. Which is it? Is anyone working on a mobile version of this app?
1
vote
1answer
115 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 ...
1
vote
2answers
551 views

Why does only the earliest transaction matter for double spending?

On page 2 of Bitcoin paper, it says: The problem of course is the payee can't verify that one of the owners did not double-spend the coin. A common solution is to introduce a trusted central ...
0
votes
1answer
115 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 ...