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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How to create a double spend to prioritize a new transaction over a previous unconfirmed transaction?

I'd like to generate a double spend transaction and increase the gas fees over the previous, unconfirmed transaction that has been stuck for a week. I know there's other answers regarding double spend ...
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56 views

Why don't bitcoin nodes invalidate new blockchains that don't contain all the data of the old blockchain?

If nodes only accepted new valid blockchains that contained all the data of the old blockchain, then miners will still be able to add blocks to the current blockchain because their blockchain will ...
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Duplicate Transaction Prevention

I'm trying to understand Bitcoin a bit more and I'm struggling to find an answer for this scenario. Say for example I have access to a wallet and I have give a person on the other side of the world ...
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38 views

What were some discussed and current potential issues with pre-forked Bitcoin coins from August 2017 that have never moved since then?

I was speaking to a friend that mentioned that there were issues with pre-forked Bitcoin coins from Aug 2017 that never moved. He wouldn't tell me exactly what the potential issue was, but what were ...
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155 views

Would first-seen prevent a double spend attack?

It takes approx. 8 seconds for a transaction to propagate through the entire Bitcoin network. If we got rid of the concept of replace-by-fee and replaced it (no pun intended) with a first-seen ...
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56 views

Does difficulty adjustment apply when you mine in secret?

Imagine you have an enormous amount of hashpower (say a nation state level attack) and you mine in secret. Does the difficulty adjustment apply specifically to your secret chain? Because that would ...
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33 views

Do you have to keep broadcasting transactions until mined?

From what I know, you can broadcast a transaction including input addresses, output addresses, and amounts, which is signed by your private key. I often hear that your transaction might not be mined ...
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93 views

Mitigating a Double Spend Attack by Punishing the Attacker?

One of the main reasons it's not safe to accept Bitcoin with 0 confirmations is due to the possibility of a double spend (where Mr. Scammer first sends 1 BTC to Alice and then creates an identical ...
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63 views

Safely Accept Bitcoin Payments with 0 Confirmations [duplicate]

GAP600 is a service (that has processed $5 billion in cryptocurrency) which allows exchanges and payment service providers to process Bitcoin payments instantly (0 confirmation trx). It guarantees a ...
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31 views

Is PoW and consensus unnecessary without double spending?

Satoshi's whitepaper claims that the reason there must be a consensus on all transactions is to solve the problem of double spend. I'm curious then, how would a non-consensus based system work if ...
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61 views

Notable examples of double-spends

Do you know any real-world examples of double-spends, where the second transaction was accepted to the block? There's https://doublespend.cash/ for BCH but for BTC I would like some examples where the ...
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66 views

why is transaction history from genesis to date necessary to store on the blockchain to prevent double spending?

I am beginning to understand the mechanism of bitcoin blockchain, and I was wondering something. The transactions history represents the 'state' of the bitcoin at any point (or EVM according to the ...
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Why can the race between the honest chain and an attacker chain be characterized as a Binomial Random Walk?

I am not familiar with Bitcoin, hope someone can tell me why. Thank you! Let's consider the following scenario. The probability of the attacker finds the next block is q and the probability of the ...
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52 views

How the bitcoin network solves the double-spending problem by adding all the transactions that happened at the same time into one block

According to my research, I understand if person A sends 2 BTC to person B and at the same time person A sends the same input to himself before the input is considered as spent. So, now there will be ...
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89 views

how does bitcoin solve the same chain replay attack?

Let's say I send 10BTC to Bob. I have 30 BTC. So after transferring, I should have 20. Now, after I transfered 10, transaction can be copied and broadcasted to the network again by Bob(he might have ...
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44 views

double spend the mempool to outbid an attacker

if I spend some input in a tx and a few seconds later spends the same input with other inputs in another tx with higher fees. If the first tx is still in the mempool would the 2nd tx replace the first ...
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33 views

How does longest chain propagation take place in bitcoin?

Let's say the valid blockchain that Node A has is: B1->B2->B3 Now, I am gonna cheat since I have lots of computing power. What I do is I download the above blockchain that Node A has and start ...
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52 views

How to find if two transactions in mempool are conflicting?

There are lots of transactions over the mempool of the bitoin. However, there might be double spends. How can we verify whether two transactions are conflicting, i.e. they are double spends of a ...
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49 views

Which transaction would get confirmed in an uncongested network?

Scenario: Mallory sends some bitcoin with a $1 fee Later, Mallory double spends her transaction with a $5 fee A new block is found In an uncongested network with an average transaction fee of ~20 ...
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36 views

Could it be possible to secure transactions against double-spending with other utxos?

I'm new to Bitcoin Script, and I was wondering if it is possible to use funds from one utxo to "insure" that other utxo will not be double-spent (until the Lightning Network will save us all). Suppose ...
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53 views

Exchange Confirmation Requirements

What does the minimum confirmations required for a deposit mean for the security of exchanges? For example, Coinbase requires 3 confirmations for Bitcoin deposits. Suppose an adversary deposits 10 ...
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4answers
191 views

If two parties submit a conflicting transaction between each other, how does the network decide which one is correct?

Let's say parties A and B both submit a transaction to the blockchain with a different version of what happened. Party A submits a transaction saying Party B gave him 3 BTC and Party B submits a ...
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76 views

Cryptocurrency acceptance

I heard that the recommended waiting confirmation time for a bitcoin transaction is 6 blocks/ 1 hour. So a shop which lets its customer to pay in bitcoin without any waiting for confirmation would ...
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54 views

Handling “dead” (double-spent) transactions in my mempool

Say I receive transaction A and it is in my node's mempool and unconfirmed. Then a block gets mined directly, which spends one of transaction A's inputs, rendering transaction A invalid. What can I ...
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Double spending problem in Bitcoin

Suppose Alice sent 2 bitcoins to Bob, Bob ships the product to Alice, then Alice sends 2 bitcoins to herself. Why is this a problem ? If both the transactions are approved then also Bob gets his 2 ...
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If I were executing a 51% attack, would I be broadcasting my state of the network to nodes?

In the scenario where an entity has control of greater than 51% of the hash power and wishes to build a longer chain where they double-spend previously confirmed transactions, do they broadcast the ...
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113 views

How does the blockchain prevent spending money during a “short fork”?

I'm currently reading "Mastering Bitcoin" (i haven't finished it tho, but i don't see my answer and it bother me so I prefer asking it here) and there's something i don't understand. So from what I ...
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60 views

Understand double spending through an example

Let’s suppose you have 1 BTC which you try to spend twice. You made the 1 BTC transaction to a merchant (Transaction T1). Now, you again sign and send the same 1 BTC on another Bitcoin address to try ...
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1answer
71 views

What happens if I spend a double spend?

Given I can receive a double spend and potentially re-spend it after 1 confirmation, what happens to that transaction once the double spend is detected during a blockchain reorg?
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383 views

Which wallets support double spending?

Which wallets support double spending? i.e. cancelling a transaction with 0 confirmations by using higher fees
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Double Spend Behavior on First Network Propagation

Supposing there is a double spend, call the transactions T1 and T2. If someone propagated both transactions within a short space of time to the network, of course only one of them can make it into the ...
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241 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 ...
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82 views

How to prevent double spending Bitcoins?

If I create a transaction, my node will check my UTXO's and if i have enough BTC to do this transaction it will be mined. So let's say I want to spend 12 BTC to Anna. The System will check if i ...
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576 views

Does proof-of-work contribute directly to prevent double-spending?

I know similar questions have been asked before (e.g. How proof of work prevents double spend) but I'm struggling to visualise the solution to double-spending being directly reliant on proof of work. ...
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Bitcoin, BTC.com and monitoring double-spend attempts

I'm reading Analysis of hashrate-based double-spending article. On page 10 there's a table listing probability of successful double-spend attack in relation to required number of confirmation. ...
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2answers
278 views

Can a malicious Internet Service provider launch a double spend attack?

If a malicious internet service provider completely controls a user's connection, can it launch a double-spend attack against the user? How much computational effort would this take?
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Who first defined/coined The Double-Spending Problem?

The Double-Spending problem is a variant of the Byzantine Generals Problem which has a nice write up by Lamport, Shostak and Pease. But who first coined/defined the specific Double-Spending problem? ...
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3answers
152 views

What happen when 2 transactions with one doublespending the other reachs the same block?

Let’s have 2 transactions. The second one is duplicating Input of the first one. Both have very high fees so they are selected by miner to be included in the same block but before passing validation (...
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1answer
533 views

Proof of Stake - double spending

I'm unsure how Proof of Stake prevents double spending. In PoW it's evident that I need 51% of the hashing power of the network, to "overtake" the real chain with my fraudulent fork. But what stops ...
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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. ...
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Why isn't the block hash used to calculate accumulated work?

Why is this idea flawed? It doesn't seem to be a bad idea at first, because the miners should be incentivized to extend existing chain, instead of to "remine existing blocks", since such "remining" ...
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2answers
191 views

Can two or more transactions sent from the same address be mined in the same block in Bitcoin's blockchain?

Imagine a person Bob has 10 bitcoins in his wallet. He wants to send 5 bitcoins to Alice and another 5 bitcoins to Uncle Tom simultaneously (in separate transactions). Will both Bob's transactions be ...
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double spend attack: Is this actually true for the more time progress the higher the probability of success for attacker

I'm new here. I have a question here. Some experts keep saying that this assumption isn't formally correct and I don't really understand why or why they might be wrong. In the double spend attack; ...
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Why “double spent” can only happen if attacker controls 51% (or more) of the network compute power?

As per many descriptions block hash is calculated based on it's headers and nonce field. The latter gives a chance to get the value that is less then a target by incrementing it. If it's a lottery why ...
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Sybil attack with IOTA? [closed]

IOTA is one of the DLTs uses DAG (Directed Acyclic Graph) as data structure. The solutions to attacks proposed by IOTA white paper seems unconvincing, in particular, in case of double-spending, it ...
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110 views

What does a double spend (CVE-2018-17144) look like if I gettransaction it?

Just wondering what the output from gettransaction (or should I be using getblock?) would look like if I passed it a txid(or blockhash) that contained a set of transactions that exploited the double ...
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Is a 51% attack on bitcoin likely?

Given that the majority of bitcoin processing is done in China (source: https://bitcoinmagazine.com/articles/report-links-74-bitcoin-mining-china-sees-threat-network/), is it possible for a single ...
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Regarding CVE-2018-17144 and test cases

Regarding the serious bug found (CVE-2018-17144) I am note sure if I understand the full scope of it correctly. As far as I understand, any block containing a double-spend of a transaction output ...
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Are bitcoins (or fractions of bitcoins) labeled with IDs?

Many sources describe the double spending problem by saying something like "people cannot be able to spend the same bitcoin twice." [1][2][3] So are bitcoins, or the smallest allowable bitcoin ...
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51 views

double spending problem

Why is double spending a problem. Suppose I have 1 bitcoin and I intend to send 1 btc to Alice and 1 btc to Bob. Once I send 1 btc to Alice, UTXO of 1btc will be unlocked,transferred to Alice.No ...

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