Questions tagged [attack]

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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2answers
14k 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
37k 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?
21
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1answer
555 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 ...
19
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6answers
7k views

51% attack - apparently very easy? refering to CZ's “rollback btc chain” - How to make sure such corruptible scenario can never happen so easily?

I was shocked to see binance CZ comment to literally "roll back" the bitcoin chain by just "calling" in some favors from "friendly" Asian miners . This ONE person could effectively do it??? I mean ...
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3answers
6k views

What are the risks of using Strongcoin.com as an online wallet?

Strongcoin claims it is "The Safest way to store your Bitcoins. The only Bitcoin e-wallet service that's not vulnerable to security breaches. Your Bitcoin keys are encrypted in the browser." As I ...
16
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2answers
7k 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 ...
15
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2answers
5k views

Why do we call it a 51% attack instead of a 50% attack?

From the Bitcoin paper: p = probability an honest node finds the next block q = probability the attacker finds the next block qz = probability the attacker will ever catch up from z blocks behind qz ...
15
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3answers
4k 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 ...
14
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3answers
7k views

Attacking Bitcoin with a supercomputer

The difficulty in Bitcoin is recalculated every 14 days. What if immediately after this difficulty adjustment someone targets Bitcoin nodes with a supercomputer and start creating new blocks? Such ...
14
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8answers
992 views

bitcoins from the future

It is likely that the Galaxy Note 2 will be launched in August. As it has taken two weeks to mine my very first bitcoin, it seems unlikely that I will have mined enough to purchase a Note upon ...
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2answers
825 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 ...
11
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2answers
2k 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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3answers
4k views

Why can't mining pools provide fake transactions within the generated blocks?

Suppose Alice wants to add a fake transaction where she receives X ammount of BTC. I understand that in order to add that transaction to the blockchain she would have to compete against all the other ...
10
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3answers
2k 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 ...
10
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3answers
790 views

Flaw in Bitcoin protocol regarding incentives to share transactions

Once the 50BTC per block rewards have halved many times and the transaction fees start to become the primary reward for miners, it sound like there is incentive for miners to not pass on transactions ...
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2answers
2k 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 ...
10
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4answers
585 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 own ...
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2answers
2k views

Which blocks get to be checkpoints?

Which blocks get to be checkpoints, and why is one block chosen to be a checkpoint, rather than another block? And where can I find a list of checkpoint blocks?
9
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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?
9
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1answer
128 views

Attack the network by temporarily adding hash power?

Could a malicious actor (e.g. government) attack the network by introducing significant compute power into the network, and once the difficulty grows very high, withdraw all resources from the network....
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3answers
488 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 ...
8
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4answers
567 views

Would any of the current botnets be able to launch and sustain a 51% attack?

The "owners" of botnets probably runs them as businesses, meaning that they will always seek profit-optimization. Do you believe that it is a matter of time before they will seek to launch and sustain ...
8
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1answer
1k views

Why does Bitcoin no longer have checkpoints?

I've read that checkpoints in Bitcoin were removed because they were not preventing any meaningful attack. Why should a regular checkpoint not prevent majority attacks? For instance, if a checkpoint ...
8
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1answer
2k 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
1k views

What prevents similar time-warp attacks in Bitcoin as happened to Verge?

Right now (may 2018), Verge (an altcoin with proof of work) was attacked by time-warp attack. More can be read here https://blog.theabacus.io/the-verge-hack-explained-7942f63a3017 What exactly ...
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2answers
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?
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1answer
1k 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
1k views

Miner modifies unconfirmed transactions and put it into the block

Is is possible that a miner modified a unconfirmed transaction (like changing the output of transaction to the miner himself) and put it into the local block, and after 10 mins the miner luckily ...
7
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1answer
284 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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4answers
235 views

Do no-fee transaction represent a greater risk if the product is delivered instantly?

Let's say I want to accept payments instantly on a site for digital downloads. So I publish an address and wait for the unconfirmed transaction, I see the transaction and release the digital download....
7
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3answers
408 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 ...
7
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1answer
406 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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1answer
1k views

What are the potential attacks against ECDSA that would be possible if we used raw public keys as addresses?

According to this answer about why addresses are hashes rather than public keys there are potential attacks that are possible if you have the public key rather than the address, what are these attacks?...
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6answers
4k 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 ...
6
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2answers
616 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 ...
6
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1answer
886 views

What is time warp attack and how does it work in general?

I am trying to understand the recent time warp attack on verge but since the attack is universal across all POW block chain i figure I could also ask here since people here are .. more knowledgeable. ...
6
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2answers
2k 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 ...
6
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1answer
1k 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 ...
6
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1answer
233 views

Have network DDoS attacks ever been successful on any coin?

Has a cryptocurrency network ever been fully DDoSed so that the blockchain did not advance during the attack? If so, which one and how?
6
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1answer
460 views

What is the maximum number of signature check operations a transaction script can request?

As transaction size, the number of signature checks per transaction can affect client performance and the inclusion of many O_CHECKSIG opcodes could be used as a tool for denial-of-service attacks. I ...
6
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2answers
215 views

How did transaction malleability/DDOS attacks allow an exchange's internal accounting system to get “out of sync”?

This Coindesk article says that: “So as transactions are being created, malformed/parallel transactions are also being created so as to create a fog of confusion over the entire network, which ...
5
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1answer
4k views

Understanding a Bitcoin Double Spending Transaction by Performing one on yourself

Everyone talks about preventing a double spend transaction, but how does one do one to yourself in order to better understand the steps involved by the attacker? What is required to do a double spend?...
5
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2answers
621 views

How to perform a double spend attack in websites that accept transactions with 0 confirmations?

To perform a Finney attack or a 51% attack I need to have lots of computational power, but in this case (a website that accepts transactions with 0 confirmations) it seems to me that I only need to ...
5
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1answer
113 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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3answers
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 ...
5
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1answer
91 views

Can corrupted unspent transaction outputs list leading to higher than expected fee be seen as an actual threat?

Let's imagine, an attacker managed to corrupt your local list of unspent transaction outputs (or a blockhain explorer you use) in a way that certain unspent transaction outputs seem to hold less coins ...
5
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2answers
148 views

Current block vs whole block chain attack

If an evil computer network wanted to attack Bitcoin, would they need to have more computing power than the present Bitcoin network and then attack a current block, or would they need even more to go ...
4
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3answers
390 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 ...
4
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3answers
1k views

How to make PoS system work?

In a r/bitcoin I've found the following statement: I think it should be noted that this paper covers a "pure" PoS system, but there have been some hacks to PoS systems to make them "work" (work ...