Relates to attempts to harm the Bitcoin network. In cryptography, an attack is a method/technique to break the code. Bitcoin also has to deal with other types of attack, such as double spends and denial of service.

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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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1answer
51 views

Probabilty of a Race Attack in time t with hashing power q

I read the original Satoshi's paper on bitcoin as well as Rosenfeld's paper on "Analysis of hashrate-based double-spending". However, they don't answer my question, which is as follows. Let's assume ...
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1answer
84 views

Is the scriptPubKey of a previously unseen transaction in an incoming block checked? If so, where?

Today I was reading bitcoind src, and trying to find out where scriptPubKey is executed when a node received new block with transaction, for example transaction from new block may not be exist in ...
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1answer
73 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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1answer
92 views

How many bitcoins would it require for a sustained DOS attack on bitcoin network?

How many bitcoins would it require for a sustained DOS attack on bitcoin network? Without transaction fee, how many bitcoins would that be? How many transactions could we generate with 1 BTC ...
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385 views

Have any SPV users lost money because they accepted forged bitcoins?

I'm making a list of real-life examples of occasions where bitcoins were lost to various known attacks. One of these known attacks is that lightweight (SPV) wallets can't verify whether a transaction ...
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1answer
83 views

Implicit/Tacit mechanisms in Bitcoin Core disclosing Selfish Mining

I'm referring to the selfish mine attack described by two researchers from Cornell University who describe a "possible" attack with lower than 51% hashing power. Now it's interesting to know what ...
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117 views

Which release fixed CVE-2010-5141 (attacker can spend any coin)

This post by Mike Hearn relates an interesting bit of history: When Bitcoin was first released, it contained two completely fatal bugs that made the entire system worthless. Fortunately, they were ...
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2answers
209 views

Simultaneously Solo and Pool Mining

It's possible to send shares both to a localhost GBT "pool" (e.g., Bitcoin Core's) and to a remote Stratum pool.* Now, if I discover a block, won't both my localhost GBT "pool" and the remote pool ...
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105 views

How does bitcoin prevent this network splitting attack?

How are malicious nodes prevented from, after getting the nonce of a new block found by someone else, broadcast it to the other nodes claiming it to be its? Also, how does the bitcoin system solve ...
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114 views

How can one simulate and analyze attacks on the Bitcoin network?

Are there any other platforms or tools beside TestNet where I can simulate and analyze various attacks like double spending (finney/block withholding attacks etc.)?
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92 views

Pseudo-Node and putative attack vectors on the network

Pseudo-Node is discussed here on Reddit's /r/Bitcoin Essentially it functions to relay calls from connected nodes in a random fashion. This was an experiment into how easily can full nodes be ...
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49 views

Is it possible to run a simple attack on a previous version of the client in testnet mode?

I need to simulate an attack locally or in testnet (if possible) for academic purpose, on an old and bugged version of the bitcoin core client. I am in posses of test BTC in the last version. I want ...
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1answer
167 views

What if some group of people start sending small transactions from wallet to wallet just to make the blockchain bigger?

What if some government start using their computers to move the tiniest amount of Bitcoin possible, from wallet to wallet, just to make the blockchain REALLY big? Is this possible? And also, is it ...
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2answers
205 views

How safe is bitcoin with regard to a random address generation attack? [duplicate]

Imagine an attacker implementing something like the following pseudocode on the fastest ASIC farm money can buy: attack(blockchain, my_address) addresses = ...
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731 views

When to worry about 1-confirmation payments

A customer sends me a payment for some digital good at my service, where delayed delivery is a deal-breaker, so I only wait for 1 confirmation by the network before releasing the links for the ...
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1answer
140 views

How does namecoin and other merge-mined coins prevent pre-mine attacks?

So, namecoin supports merged mining against bitcoin. My understanding of the merged mining protocol is that basically miners can use the primary coin's POW solution to solve the aux coin's block. It's ...
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159 views

Specifics on “Race Double Spending Attacks”?

Hi guys I am doing some research on double spending in the bitcoin network several ideas have been confusing me: In prevention of Race attacks, merchants are advised to "connect to a large random ...
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3answers
237 views

What happens if I fork an older block chain and rejoin the network later?

Let's call it a "time machine attack". Suppose I have an isolated network of n clients with a significant hash rate, install my client software on that and start mining on an older blockchain. Since ...
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4answers
240 views

Wouldn't the “malleable transaction” attack be foiled by common sense?

I'm trying to understand the malleable transaction attack, as it seems to me that only a rather careless operator would be vulnerable in the first place, as described below. Mainly to clarify my ...
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1answer
100 views

Isn't bribe smearing possible because no payee signature is required?

The Bitcoin protocol does not require the payee to sign for a payment; only the payer signs (the payer signs a hash of the payee and payer's public keys). In other words, a payee signature is not ...
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2answers
687 views

Is there a real threat of so called “>50% attack”?

According to Bitcoin Wiki attacked who has majority of computing power of the bitcoin network can successfully do some nasty things such as potentially book double-spending or prevent transactions ...
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1answer
63 views

How the Bitcoin community will handle attacks on a Client's code?

I have some thoughts about the following scenario. The brightest future. The Bitcoin becomes a very popular and liquid currency all over the world. Some serious financial or political parties may ...
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1answer
485 views

What attacks are possible with a malicious bootstrap.dat?

The standard Bitcoin client normally needs to download the entire blockchain from the p2p network when first installed, but a shortcut is to provide it with a snapshot of the blockchain (at some point ...
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6answers
2k views

Is it possible to spam the bitcoin network with 'dust'?

Someone could buy or mine bitcoins, and send them in small transactions all day to spam the blockchain. Is this possible? And could this mean the end of the trust people have in bitcoin? edit: And ...
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3answers
271 views

Would it be feasible to attack the bitcoin network by buying and deleting large amounts of bitcoin?

Could a government, determined to stop bitcoins, just buy a lot of bitcoins and delete the wallet afterwards? Are the bitcoins gone then?
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210 views

Attack on bitcoin network with modified client?

Scenario: Mallory, Alice and Bob found block on their farm. They disconnect from internet, simulating split and change all of nodes in their segment to malicious. Malicious nodes decrease ...
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2answers
743 views

What happens if Bitcoin itself is obsoleted by another digital currency?

Unless Bitcoin is replaced with a Bitcoin-compatible currency, I believe that all holders of Bitcoin will be out of luck when the day comes that it is obsoleted by a superior system, as inevitably ...
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195 views

Government disrupting reception of bitcoins. Is it possible?

I was thinking of a very specific scenario: Suppose we have a new organization, let's call it "WikiLeaks2", which receives donnations mostly in the form of Bitcoins. Suppose a national government ...
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3answers
2k views

Why do pools get so often DDoS attacked?

In other words: who has incentives for attacking pools? Do you think it's the government?
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680 views

What is the Ripple equivalent of the “51% attack?”

In Bitcoin, if a participant gains control of more than 50% of the hash power, they can execute a double-spending attack. The "attack" could come from within, say if the existing powerful miners ...
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0answers
24 views

Could the target become unreachable? [duplicate]

As far as I understand it, the target T is a floating point number that is adjusted based on the moving average of the difficulty of some previous transactions. Mining a block happens when somebody is ...
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2answers
818 views

DDoS on big mining pools: a quick way to 51%?

Slush's Pool, the second biggest mining pool around, is currently down, allegedly due to a DDoS attack: News 16.04.2013 Pool is under DDoS attack. I'm working on recovering the service back to ...
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1answer
218 views

Can someone saturate the network?

Suppose I have 2 wallets and 1 bitcoin and I write a program to make transfers of 1 satoshi from one wallet into the other. No suppose I have 100 bitcoins. Wouldn't that saturate the network?
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803 views

Developments to prevent 51% hack [duplicate]

How might Bitcoin be made impervious from attack by large monied interests that could atttack with a brute force majority hashrate hack?
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994 views

Could a mining pool attack Satoshi Dice?

Is it possibile for a mining pool to attack Satoshi Dice? A strategy might be: bet on Satoshi Dice and if the bet wins, do nothing, if it looses, don't put the transaction in the block (try to double ...
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2answers
351 views

Could miners steal money?

I've been reading around: https://en.bitcoin.it/wiki/How_bitcoin_works What prevents a miner's block from being accepted across the network if the hash checks out when miner forges transactions in ...
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1answer
119 views

I'm developing on the Test network. Are there any “rules” or communication methods I should adopt?

I'm testing a C# port of the client on the Test network and need to test for a variety of conditions. Should I communicate to others regarding my actions on the network? If so, what method of ...
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2answers
484 views

What stops miners/nodes lying about what time a block was mined?

From what I understand, the difficulty required by the proof-of-work in bitcoin is a function of block history, specifically the average time between last ~2000 blocks, with the intention that its ...
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713 views

How much would it cost for a government to undermine Bitcoins?

Articles by for example the Economist stating that Bitcoins are being used for drug trading (Silk Road), I believe that the biggest risk to Bitcoins is that a government will pull a stunt similar to ...
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3answers
4k 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?
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234 views

How do mining pool payout methods affect the cost of executing a block withholding attack?

I'm wondering how each payout method (PPS, DGM, PPLNS, Proportional, etc) influences the cost of executing a block withholding attack. Does it matter how the payout method places variance between ...
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2answers
2k views

What is a block withholding attack?

How can a block withholding attack be performed, what would be its purpose and who is it a danger to? Edit: when I posted this I was thinking about withholding a block you mined in a pool. But ...
18
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2answers
4k 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".
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3answers
412 views

How can I assure my consumers they are actually paying the correct person? (prevent MITM attacks)

There are many network level attacks that give someone Man in the Middle ability to replace my Bitcoin address with their own. Since there is no way to cancel a transaction, and the best practice ...
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2answers
2k views

How can I find well-connected nodes?

If I am a merchant accepting 0-confirmation transactions I should protect myself against race attacks. Several resources state that I should configure bitcoin daemon to not listen for incoming ...
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3answers
843 views

Does the protocol ensures that private keys are unique?

There is a very very low chance for the same private key to be generated. (source) However, what happens when my generated private key matches a private key that is already used? Does the protocol ...
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3answers
364 views

What nodes are best for lessening the risk of loss from a race attack

A successful race attack is one where the payment recipient's node receives a spend transaction yet the next block that is mined has a different transaction that spends the same coin. Thus the ...
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779 views

What does a double spend look like?

What does a double spend look like? Can anyone link to an example on blockchain.info? Will invalid half of the double spend simply remain at 0-confirmations, or might it ever reach 1 or 2? Will the ...
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2k views

What is the story behind the “Linode problem”?

What is the story behind the "Linode problem"? How did the service become compromised and what has exactly happened because of it?