Tagged Questions

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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Who would accept confirmations of invalid transactions in a 51% attack?

My understanding is that honest nodes work on the longest valid block chain. Suppose a dishonest node confirms an invalid transaction. If that node manages to continue producing confirmations at a ...
2
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1answer
58 views

Why are broadcast checkpoints considered bad?

warren, a LiteCoin dev, said of Peercoin: Good Luck Removing PPC's Centralized Checkpoints Regarding PPC... these amount to empty obfuscating defensive excuses. Sure he wants to remove the ...
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1answer
80 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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2answers
252 views

Does selfish mining actually give an advantage in the absence of transaction fees, difficulty changes, and economic effects?

I am reading the Cornell selfish mining paper. In it, their main argument is that a selfish miner can increase the ratio of the blocks he mines relative to the honest miners. I do not dispute this. ...
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2answers
164 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
207 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
91 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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1answer
66 views

Does a 51% attack depend upon difficulty?

Does increasing difficulty also serve to decrease the probability of a 51% attack? It seems that since difficulty is the same for all, this is not the case. Is that correct? If difficulty were ...
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2answers
288 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
58 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 ...
3
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1answer
349 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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5answers
1k 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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1answer
173 views

Has the payment protocol – which is supposed to protect against Man-In-The-Middle attacks – ever been implemented?

The two main problems generally mentioned that payment protocol “BIP 0070” (Andresen, 29-07-2013) is supposed to solve are usability and protection against Man-In-The-Middle attacks. In the latter the ...
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3answers
268 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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2answers
187 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 ...
1
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1answer
136 views

What is the probability of generating 6 sequential blocks, less than an hour?

I'd like to determine the probability of a fairly powerful miner (or pool) generating 6 sequential blocks in an hour. (so they would rebroadcast it later) For example, given Hash/second: X A ...
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2answers
621 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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2answers
74 views

Techniques or proposais to require transactions to be included in a block?

As it stands now, a miner (or mining pool) can discriminate any transaction for any reason if they are running a custom version of code. Suppose an evil and powerful mining pool decided to hash ...
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2answers
181 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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1answer
578 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
22 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
140 views

How long does it take to go from 51% hash power to 100% hash power?

Once an attacker has acquired 51% hash power, is it possible to quickly get to 100% hash power by simply refusing to build on blocks created by other mining nodes and therefore discouraging mining ...
7
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1answer
700 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 ...
4
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1answer
202 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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1answer
128 views

Feasibility of a “High horsepower” attack (based on difficulty -4x adjustments)

This is really Part 3 of this earlier question. Given that the QT client is hard coded to never adjust difficulty more (or less than) a factor of 4... What realistic scenario would cause the ...
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1answer
50 views

What's the impact of net-splits on block generation… over a long period of time?

Part 1 For this question, assume the overall hashrate of the environment is constant. If 25% of the network hashpower were to be isolated (Australia had no Internet for example), what is the effect ...
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2answers
719 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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1answer
524 views

Can a Finney Attack make SatoshiDice betting profitable? [duplicate]

Can a Finney Attack make SatoshiDice betting profitable? If you perform a Finney Attack whenever your bet fails (by replacing it with a transaction to yourself), then would it make betting profitable, ...
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1answer
113 views

Possible to include a per miner transaction to prevent withholding and independent rebroadcast of a solved block?

Update: This is a bad idea because it simply won't work, but it did help me understand what happens between a Miner and a Pool. And if you missed it in the comments, read @Meni's PDF for a threat and ...
8
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1answer
904 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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3answers
698 views

Is the minimum amount of money required to purchase >50% hash power equal to max worth of all existing bitcoins?

20 BFL Bitforce Mini Rigs (each, $30k) will give about 30THash/Sec hash power for $600k. That's way above 60% of hash power of then total 51THash/Sec. 10.694M total Bitcoin * $18.5 current mtgox best ...
4
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1answer
107 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 ...
3
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2answers
350 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 ...
9
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2answers
650 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 ...
6
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3answers
1k 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?
3
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1answer
223 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 ...
6
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2answers
1k 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 ...
10
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2answers
2k 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
318 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 ...
5
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2answers
1k 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 ...
8
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3answers
699 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 ...
6
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3answers
330 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 ...
5
votes
1answer
587 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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1answer
1k 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?
2
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1answer
418 views

What is the story behind MyBitcoin?

The name of MyBitcoin eWallet comes up quite often here and there. What is the story behind it and the attack on it they claimed occurred?
12
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1answer
636 views

Was a timejacking attack ever performed?

The timejacking attack appears to be a pretty straightforward attack to pull off successfully. I was wondering, whether it was ever performed and documented somewhere, or was it just theoretically ...
2
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1answer
117 views

Is an attack on a local bitcoind via an img or embedded flash viable?

In this thread on the Bitcoin forums it was suggested that a local attack on bitcoind might be possible through malformed img tags or (more likely in my opinion) through embedded flash. This also ...
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1answer
2k views

What is the story behind the attack on Coiledcoin?

A couple months ago I came across the news about Eligius pool being used to destroy an AltCoin called Coiledcoin. As I understand the miners of the pool did not know their hashing power was used in ...
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3answers
1k views

What can be done about the no-transaction block relayer (currently 71.123.170.150)?

An unknown major solo miner (currently IP 71.123.170.150), most likely a botnet, is relaying blocks with zero transactions. Two weeks ago this miner constituted ~15% of the network, now it constitutes ...