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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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 ...
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1answer
201 views

How does headers-first prevent fill-disk attack?

Checkpoints prevented an attack where a node could mine many many low-difficulty blocks from an early point in the blockchain and serve those blocks to syncing nodes who would see their disks fill up. ...
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1answer
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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. ...
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1answer
152 views

What exactly is selfish mining?

What is a selfish mining attack MonaCoin suffered from?
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1answer
2k 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 ...
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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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1answer
153 views

Is the bitcoin blockchain really non-corruptible? [duplicate]

Some people say that proof of work is better than proof of stake, because it's not possible to rewrite the whole blockchain on-spot. One would need to "re-mine" everything. But I think this is not ...
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4answers
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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 ...
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1answer
168 views

Is "fee higher than block reward" attack possible?

Imagine the following scenario: I send you 1000 BTC. After 6 confirmations, you give me what I bought. I create another transaction with 900 BTC to my own wallet and 100 BTC as transaction fee, using ...
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5answers
851 views

Is this man-in-the-middle double-spending attack against Bitcoin viable?

There is an almost trivial double-spending attack against Bitcoin if an attacker has a MITM (man-in-the-middle) attack against a victim: the attacker prevents all blocks from being seen, and replaces ...
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2answers
179 views

What happens if an ISP isolates a portion of nodes?

I came to believe that an ISP can easily detect full nodes, BTC connections and isolate them from reaching any other nodes. When and if an ISP decided to do so, could they easily perform a 51% attack ...
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1answer
440 views

resilience to sybil attack - public vs private

it appears that although not totally water-proof to Sybil attacks, Bitcoin network seems quite resilient to these kind of attack Preventing Sybil attacks. Is it true to assert that permissioned or ...
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1answer
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POW based blockchains systems Majority Attack

TL;DR: With only 30% of network power a Majority Attack is possible and profitable. Am I missing anything? Generally speaking, blockchains based on Proof-of-Work authentications are using amount of ...
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2answers
259 views

Cryptocurrency with addresses that cannot collide?

I had originally posted the following question here: Is it possible to have a cryptocurrency based on email address? And now I have come across The Large Bitcoin Collider I have read on Bitcoin ...
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1answer
288 views

What prevents rewriting the history of a chain with a different difficulty? [duplicate]

It looks like the difficulty is deterministic, but only if the timestamps are trusted. What's to prevent a large miner from starting back much earlier in the chain (when difficultly was miniscule) ...
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1answer
108 views

What if some attacker forks blockchain from height 1 with a constant difficulty 1?

I've been reading Satoshi's paper recently. There's one thing I cannot think through. That is because the target will limit the block production speed to 2016 blocks per two weeks on average no ...
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How does the Bitcoin network deal with bad actors?

Can someone explain at a high level how the network deals with bad actors (either intentionally (ie- attacker) or unintentional (ie- misconfigured node or a node running outdated code, forked code, ...
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1answer
145 views

How much money would it take to bribe the majority of miners to attack the system?

I think this question is just a re-formulation of the 51% attack, but it has me thinking: miners are monetarily incentivized to not perform a 51% attack, but there must be some amount of money will ...
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1answer
62 views

Can a bad actor omit an unspent address from a pruned chain?

This isn't a problem today, because if I want to run a pruned node then I still have to download the whole chain, but it sure would be nice if I could just download a pruned chain instead and validate ...
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1answer
126 views

Can a Bitcoin ( or any other cryptocurrency ) be compromised with a large botnet/s?

I'm new to cryptocurrencies, so I recently read the paper from the Satoshi Nakamoto ( link is here ) to know a little bit more about the Bitcoin.And I saw this statement: What is needed is an ...
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1answer
306 views

51% attack clarification

Im just reading a book on the basics of blockchain and I encountered a confusion regarding the 51% attack. If I'm right, it says that an attacker holding 51% or more of the network's computing power ...
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1answer
257 views

Attack vectors for difficulty retargeting with BCH and BTC?

Since the existence of BCH, miners can now switch chains to mine on. Assuming they mine greedily based on price and difficulty. Can the following attack happen and how could it be mitigated: Assuming ...
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2answers
1k views

How does changing transaction data in a block change the hash of previous block?

I am reading this article, within which it mentions that "Imagine this for a second, a hacker attacks block 3 and tries to change the data. Because of the properties of hash functions, a slight ...
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1answer
67 views

What prevents a node from sending a different version of the blockchain?

I understand that proof of work prevents a node from creating a new version of the blockchain unless they have >50% of the hash rate, but what if the attacker is also able to intercept the victim's ...
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How exactly are Bitcoin's consensus rules enforced?

There are some rules called consensus rules, for example the block generation amount. And it is said that "a change to consensus rules is a hard-fork". But how exactly are the consensus ...
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2answers
107 views

What happens if 1-way functions no longer exist?

Advances in AI and nanobiotech can radically increase intelligence to the point where unsolved mathematical problems get solved. What happens to Bitcoin (and other cryptocurrencies) if ⨕&...
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4answers
305 views

What can an attacker who controls majority or all of the full nodes do?

What happens when a strong attacker has control of majority or all of the full nodes? What damage can he do and would they be reversible?
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1answer
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Can one node receive two transactions from the same user (doublespend)?

I'm learning how the blockchain works. I've read that when someone (say Alice) send twice a transaction to two different peoples (Bob and Charlie) such that Alice has only enough to pay Bob or Charlie,...
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What stops this style of attack on the Bitcoin network?

I was having a look at the genesis block of Bitcoin earlier and noticed the difficulty was set to 1. I guess this was originally designed so just Satoshi's computer mining at this difficulty would ...
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3answers
8k 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 ...
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0answers
440 views

Can a private key enumeration attack be used to steal bitcoins? [duplicate]

Let's consider the following algorithm enumerate all of the private keys for each of the enumerated private keys, generate the relative public key and verify whether there is any unspent coin ...
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1answer
155 views

How does intial block download work at P2P layer?

A simple DOS attack while IBD could be as follows: The fresh client is currently downloading block 100. Then it is offered 10 blocks at height 101, each claiming they are the heaviest chain 9 out of ...
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1answer
255 views

Force a fork - is that possible?

I am having a question regarding forks. We had a discussion about attacks on bitcoin in class recently. One of the attacks was about how an attacker gains some advantage if he is able to mine a block ...
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1answer
164 views

How can't a malicious attacker generate bitcoins on his private network?

I'm new to the cryptocurrencies world and I'm trying to understand how all this stuff works, so expect a really noob question. Suppose there's a user which generates a number of addresses and sets ...
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1answer
928 views

Why is attacker revenue in the selfish mining disproportional to its hash-power?

It's not clear to me why attacker can gain more revenue if it does "selfish mining" attack than its revenue when it behaves honestly. I'm aware of this paper.
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Does the software to conduct a 51% attack exist?

I know that it would cost hundreds of millions of dollars to do a 51% attack on Bitcoin, but if somebody did that, bought the hardware, etc could Bitcoin Core or any other software be easily ...
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1answer
68 views

What is to stop a malicious attacker only mining 1 transaction per block?

Even without 51% of the mining power, if you have say 5% of mining power and you deliberately only mine 1 transaction in your block aren't you going to create a traffic jam of transactions and ...
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1answer
886 views

What makes HD wallets resistant to brute force attacks?

To be more specific, let's consider wallets that use 12 words as a seed. Total bit width is 132, with 4 bits used as a checksum, so the actual seed size is 128 bits. I know 2^128 allows for LOTS of ...
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1answer
882 views

What is protecting the mempool from being DDOSd?

The mempool currently seems to contain almost 60K unconfirmed transactions, and the number seems to be growing. According to this question, it seems that unconfirmed transactions are eventually purged....
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3answers
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Hacked bitcoin account.

I believe that my account was hacked: a "send" transaction occurred on my account an hour ago and I lost $62 without my raising any transaction. The transaction is still unconfirmed, how do reverse it ...
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3answers
2k 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 "...
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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?...
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Can i trace a hacker by collecting data from Bitcoin api?

In Japan, MtGox, the biggest bitcoin exchange went down and went bankrupt due to hackers. So I'm working on a project in my College to enhance security of bitcoin transactions using the data mining ...
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1answer
2k views

How does a time warp attack work?

I more or less understand how an attacker (with less than 50%+1 of the hashing power) can artificially lower the block difficulty by messing with timestamps. I also understand how such an attacker ...
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1answer
243 views

70% of nodes accept Bloom filters, despite DoS attack vector?

Could someone explain why so many Bitcoin nodes allow Bloom filtering given that DoS attacks exist [1], [2] for such nodes? According to bitnodes.21.co, right now 3879 nodes out of the total of 5515 ...
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1answer
131 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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1answer
133 views

How does a node compare two blockchains?

Let's say an attacker connects to the Bitcoin network. Let's say this attacker possesses an old ASIC HW and she used it to generate a blockchain of half a million blocks, with faked timestamps and ...
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1answer
1k 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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1answer
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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
227 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 ...