"Double-Spending" is an attack or failure which results in the same digital moneys being spent twice or more.

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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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51 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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29 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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40 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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30 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 ...
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41 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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90 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 ...
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76 views

0/confirmation race attack double spend transactions

I am developing a point of sale bitcoin app, which should accept "fast" transactions (~30 sec for merchant to accept). I researched double spending questions here already, but it is still unclear to ...
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56 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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57 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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135 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 ...
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79 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 ...
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51 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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80 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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76 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
528 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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328 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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101 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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140 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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49 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 ...
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56 views

Using Transaction with multiple outputs

Since the output can be spend only once, I am confused by transactions containing multiple recipients. For example, if Alice transfers 5 BTC to Bob and 5 BTC to David in the same transactions. In the ...
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3answers
458 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 ...
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85 views

What exactly happens when a node detects a double spend?

Does the node drop both transactions? Does the node choose which one to keep? What exactly happens? Will both transactions be rejected by the network or will one of them be eventually accepted?
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512 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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217 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 ...
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146 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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118 views

What happens if a TX was a double spend?

What happens if the 'High' risk option (one confirmation) was chosen and then the TX turns out to be a double spend in the end? Would the value deposited be revoked? Would the user be notified ...
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66 views

How do you inspect a transaction?

How do you inspect a bitcoin transaction to avoid getting scammed by a double spender? I'm buying bitcoins in cash and the seller said I could inspect a transaction instead of waiting 6 blocks. Is ...
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74 views

How to detect a race attack and re-spend the already-spent outputs?

My service automatically accepts, processes and sends payments to its users. It connects to bitcoind through its JSON-RPC API and makes use of the raw transactions interface. What is going to happen ...
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405 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 ...
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140 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 ...
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103 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 ...
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411 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?
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Why are double-spends bad? [duplicate]

In the answer to this question it is stated the bitcoind filters doublespends. What is the reasoning behind this?
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152 views

How does CryptoNote prevent a 51% attack and double-spending?

How does CryptoNote prevent a 51% attack and double-spending? I’m interested to know what is the mechanism that protects CryptoNote coins from 51% and double-spending attacks.
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523 views

Warning about possible double spend at blockchain.info

What does this blockchain.info alert mean? Warning! this bitcoin address contains transactions which may be double spends. You should be extremely careful when trusting any transactions to or from ...
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496 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 ...
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103 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 ...
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392 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 ...
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166 views

Does using Ripple to accept Bitcoin reduce risk of Bitcoin fraud?

Does Ripple reduce the risk of double-spending, or other types of issues that may crop up when using Bitcoin natively?
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32 views

Can too big hosted mining service be mitigated by allowing customers to choose mining pool?

Let's say a company is hosting mining hardware, either hosting customers' hardware or renting out the hashes produced by hardware owned by the company, or both. So the company is physically ...
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How much hashpower is needed to double-spend? Is >50% a minimum?

How much hashpower is needed to double-spend coins? Some worry only about one entity getting over 50% of the hashpower, while others are complaining (at the time of writing) about an entity having ...
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72 views

Can someone explain double spending to me?

I am restoring a backup of my Bitcoin Core wallet on a new PC. I downloaded the complete bootstrap.dat and placed it in ~/.bitcoin. I thought using the bootstrap would make things faster, but ...
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303 views

Can Bitcoin scripting be used for double spending attacks?

A standard Bitcoin transaction deposits coins into an address and then, using Bitcoin's scripting language, states that whoever wants to spend this output must be in possess of the private key ...
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1answer
46 views

Double spending race attack first transaction

In tackling double spending, does the protocol enforces that only the first transaction (and by first i mean the first transaction to be send to the network) is considered as valid ?
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60 views

Curious about a network-based double-spending attack

In their paper Two Bitcoins at the Price of One? Double-Spending Attacks on Fast Payments in Bitcoin, Karame and Androulaki outline a particular race-attack that involves the slight control over a ...
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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 ...
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660 views

How does BitCoin prevent fraud during confirmation period?

I'm trying my best to understand how bitcoin works and while I've grasped the basics, there's a lingering question: What's to stop me from spending my bitcoin multiple times during a confirmation ...
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77 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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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 ...