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 ...
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23 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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10 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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38 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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195 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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76 views

Does Bitcoin's SHA256 proof make a 51% attack more likely?

Ethereum's description says that Bitcoin's mining algorithm requires only a simple SHA256 computation, which caused the creation of specialised ASICs, which centralizes mining in the hands of a few ...
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82 views

Is it easier to conduct a 51% attack on PoS than PoW? [closed]

For those who are not familiar, one of the main selling points of proof-of-stake is that it makes it more difficult to conduct a 51% attack. The reasoning is that to conduct a 51% attack on a ...
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133 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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191 views

Does the Mt Gox attack constitute theft of Bitcoins or just a Denial-of-Service attack?

What's being reported on the news is that millions of Bitcoins were stolen from Mt Gox. But the Bitcoin Foundation blog says something different: https://bitcoinfoundation.org/blog/?p=422 ...
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158 views

Is there a way to stop a man-in-the-middle attack when communicating addresses?

Let's say you have person A who wants to pay person B. A common way for B to communicate his/her address to A is by QR code or email or some such non secure method either of which could be ...
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207 views

Why is Enjoy Sochi a malicious spam attack

I recently read the following thing on reddit: The two transactions for .00000001 BTC are a malicious spam attack. They were sent without fees, which means that if you wallet doesn't allow you ...
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405 views

Can the bitcoin network hashrate be used for a 51% attack on other coins?

Please correct me if I am wrong. The difficulty constantly changes according to the current hash rate. It changes to ensure that a block is mined every 10 minutes. If the hash rate was 1000 TH/s and ...
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72 views

History of cold boot attacks on PoS miners

Have instances of theft due to cold boot attacks been recorded? If so, is this a common problem? If so, are miners installing memory encryption software like Tresor?
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189 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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105 views

Hash speed attack

I'm discovering alt-coins. Now, I'm on piratecoin. { "blocks" : 34167, "currentblocksize" : 1225, "currentblocktx" : 1, "difficulty" : 0.14348426, "errors" : "", "generate" : ...
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660 views

Creating a fake transaction

AttackerAlice has a BTC Wallet with 0 BTC. AccompliceBob has a BTC Wallet. Is it possible to transfer 100 BTC from AttackerAlice to AccompliceBob? Suppose a BadMiner accepted this as a valid ...
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84 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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306 views

I don't understand the “51% attack” problem. Why does a mining pool have power with a 51% share?

What gives a mining pool power to maliciously dominate the system if they're mining over the majority of the coins? Profits are disseminated to miners individually. I really don't understand how this ...
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59 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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254 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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120 views

What will happen, if transaction's rate becomes very high?

Let's imagine, that the bitcoin network becomes very responsive in the future. So, that the time of exchange of transactions between peers is comparable with a time of evaluation of a bunch of hashes. ...
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56 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
303 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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171 views

Is a 51% attack really expensive?

In order to perform a 51% attack someone has to concentrate huge amounts of computing power. Obviously this would be very expensive. But in return the attacker obtains the block reward and mining fees ...
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129 views

Hashrate required for Finney attack on SatoshiDICE [duplicate]

Say I have an address with 1000 different 0.01BTC outputs. I send all of the outputs (in separate transactions) to the 48% SatoshiDICE address. At the same time, I craft a transaction for each of the ...
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833 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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142 views

Has the man-in-the-middle attack the payment protocol is supposed to protect against ever been implemented?

The two main problems generally mentioned that the new payment protocol is supposed to solve are usability and protection against man-in-the-middle attacks. In the latter the attacker would substitute ...
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264 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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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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125 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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559 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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71 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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173 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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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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518 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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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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135 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 ...
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664 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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196 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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123 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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44 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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674 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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502 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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110 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 ...
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850 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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682 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 ...
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99 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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293 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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616 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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889 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?