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 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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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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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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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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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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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
161 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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2answers
72 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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1answer
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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 2.0 [duplicate]

How is the following case handled in bitcoin blockchain? Initially Alice has only 2 bitcoins. Suppose Alice sends 2 bitcoins to herself(tr1 i.e. Alice to Alice) and then 2 bitcoins to Bob(tr2 i.e. ...
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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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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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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
59 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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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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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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1answer
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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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1answer
507 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
215 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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1answer
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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
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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
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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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1answer
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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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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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1answer
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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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1answer
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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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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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1answer
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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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3answers
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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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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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In Litecoin every single block is mined every 2.5 minutes, double spending?

In Bitcoin it takes roughly 10 minutes for every block to be mined. In Litecoin it takes 2,5 minutes. 2.5 minutes in Litecoin mean that transactions can be confirmed faster. In Bitcoin these 10 ...
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2answers
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can attacker and honest node in double spend ever tie?

in bitcoin white paper there are only attacker and honest nodes. you have p, and q for probabilities. in double spend attack, in bitcoin whitepaper, can we talk about possible tie of attacker and ...
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double spending , you can create money out of thinner air [duplicate]

I am a little confused about how doublespending is done. The basic case is basically creating transactions to the seller and yourself and simultaneously broadcasting those. This is the very classic ...
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how is the current hashing power (of the entire network) measured (in real time)?

1) does hash power refers to mining nodes only ? 2) we don't know how many nodes there are on the bitcoin network , correct ? how do we count them ? 3) would we need to know [2] in order to figure ...
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in the white paper you have 2 sides : attacker and honest node

What does it mean that there is either the attacker or honest node. This means that within 10 minutes either attacker or honest node mines a block but what about neither OR another side ? How could ...
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1answer
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what does it mean to have >51% hashing power for mining a block? [duplicate]

Can someone please shine some light on this and how it links to the analogy between honest node and attacker ? also can attacker start mining 2 blocks ahead ? or 3 or 4 blocks ahead ? In the white ...
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1answer
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Security via Proof - of - Work

I am reading Satoshi's original paper, merely for the sake of understanding the concept. I have minimal computer science background (some), mostly just mathematics. In Section 4. Proof of Work of ...
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What happens if full nodes don't check for double spends or deliberately lets a double spend TX pass and then this full node relays the transaction?

I am studying about Bitcoin and Blockchain tech via the Princeton crypto course, and it mentions that Full nodes do the following checks : i)transaction is valid with the current blockchain, ii)...
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What happens to rejected transactions ( i.e double spend or invalid transactions)?

Do they get put in an orphaned block or not get put into any block at all?
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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 ...
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Possible error in the white paper Calculations section?

Section 11 presents calculations of the probability of double spending, P(z, q), given an attacker relative hash rate q and a block count z. P(z, q) can only be understood by knowing exactly what z ...
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What can make an unconfirmed transaction (0-conf) an invalid one other than Double-spend?

It's obvious that inputs that already been spent will make the transaction invalid (pure double-spend scenario), but is there's anything else that could make a tx invalid? Invalid inputs? Invalid ...
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Can there be double spend between propagation of block chains between 2 set of peers?

It shouldn't be as simple to do a double spend. I think I am missing something here. I understand Consensus rules and P2P networking. But since a node is connected only to some limited number of other ...
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How two transactions with the same hash can cause double-spending

Let's consider following situation: Vendor owns address X. Adversary sends transaction T1 to X with hash Y and receives product from vendor. Adversary sends transaction T2 to address which he owns ...

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