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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Probability an honest node finds the next block vs. probability the attacker finds the next block

I am trying to understand Satoshi's paper [1]. On page 6 of the paper, he calculates the probability that someone can attack the blockchain from z blocks behind. He begins by defining: My question: ...
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To what extent does asymmetric cryptography secure bitcoin transactions?

Is there a specific attack or bug which asymmetric cryptography prevents during bitcoin transactions?
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Possibility of a DDoS attack

Theoretically. This is not a mechanism of any kind of attack, but It's about the "lost" coins. May be. It is just for an educational experiment. What if someone has the ability to send transactions ...
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Is this a collision attack or a 2nd-preimage attack?

This question revolves around Bitcoin Optech newsletter #51 (1) and an email thread from the bitcoin-dev mailing list (2). I asked the same question in a reply-email of the newsletter and the response ...
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Can a malicious Internet Service provider launch a double spend attack?

If a malicious internet service provider completely controls a user's connection, can it launch a double-spend attack against the user? How much computational effort would this take?
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How to re-secure a multisignature wallet if private key is stolen

Here are two attack scenarios on bitcoin private keys: 1) Assume that, BitCorp has just noticed that a Mallory has just compromised one of their servers holding their Bitcoin Private keys. Luckily,...
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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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Malicious full nodes causing denial of service attacks

To control >51% of the mining power in bitcoin is impractical due to the immense investment that will be required. Also, The Bitcoin Core client has DoS protection against malicious nodes forwarding a ...
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What are the consequences if I spoof an IP address in the node_announcment message?

According to BOLT 07 the node accountment message looks like this: type: 257 (node_announcement) data: [64:signature] [2:flen] [flen:features] [4:timestamp] [33:node_id] [3:...
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What stops miners from no longer submitting failed hashes to the network, to reduce the difficulty and block time?

As I understand it, the difficulty adjusts based on the hashrate to keep the block times at 10 minute intervals. But if Alice and Bob are the only ones mining on the network, what's to stop Alice from ...
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A question about Feather Forking attack with higher confirmations

Suppose A has 0.2 hashing power. If A is waiting for only 1 confirmation. The chance of successful attack is 0.2^2 = 0.04 = 4%. So the victim has to pay 0.04*Block reward tx fees. What if the ...
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How to find one private key from the list of 15 million public keys for the sake of experimentation?

Recently found a list of compressed public keys. The total number of 15 000 000 public keys. Practical for all compressed public keys Balance: 0.000100 BTC I do not set malicious goals. All just for ...
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Serialized transaction bigger than the actual transaction object? CVE-2013-4627

I'm surveying old Bitcoin DoS vectors and came across CVE-2013-4267, for which there appears to be little public information available. This thread should shed some light on this CVE. There's a ...
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What happens when the verification of a manipulated transaction fail?

If a malicious miner changes the amount in a given transaction, the hash value of the block changes. Thus, he has to find the required hash value again in that block. Let's say he successfully found ...
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Set up a Bitcoin full node: static or dynamic IP address?

I am trying to set up a new Bitcoin full node and my institution ISP is trying hard to not give me a static IP address for this purpose. I guess because of the concern that the node will be DDoSed, ...
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Bitcoin is attacked by China miners by screwing with the network, what will Bitcoin do?

There was a report recently (https://arxiv.org/pdf/1810.02466.pdf) that stated that China controls 74% of the hashing power. They can choose to collude and attack the network by either doing a 51% ...
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Why was this transaction accepted?

In testnet, txid:fb7a8658ec015133e36e2cf7ddf7e8c887c3a5becec2f30f24ebfe43e72f4b59 transaction has two inputs. This two inputs indicate the same txid and vout, ...
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attack bitcoin through writing data directly into output's scriptPubKeys

In this post, Steve Ellis wrote : "[...]Writing data directly into a output's scriptPubKey is not prunable[...]where as non-prunable outputs will forever create bloat and slowdown the set ...
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Is there a limit to how many blocks can be rolled back from a 51% attack?

I was wondering if we where to ever face a 51% attack is there some sort of limit as to when the longest chain doesn't matter? For example if I owned 51%+ of the network, mined 1000 blocks privately ...
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Possibility of broadcasting new block to only a fraction of honest nodes?

Consider in a block-withholding attack (aka selfish mining attack), attacker after creating a new block decides to broadcast this new block only to a fraction of network, such that eventually only a ...
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What prevents DoS based on near-valid block timestamps?

Upon receiving a newly mined block, the block timestamp validation is performed here: https://github.com/bitcoin/bitcoin/blob/master/src/validation.cpp#L3263-L3270 Q1: As for the second check (block ...
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Mining Theory: A theoretical mining based attack

Okay, so, here is my scenario: Imagine a group of miners who are mining a coin are responsible for a large portion of the hash rate on the network (let's say not quite 50%). Looking at the parameters ...
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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 ...
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Hypothetical Scenario - Address collision with address with already confirmed outgoing transaction

In a typical case of finding a collision with an address, as long as the private key provided has a consistent public key that hashes to the address, then the coins in that address can be spent. The ...
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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 ...
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How prevalent are coin attacks with botique altcoins?

I have deployed several altcoins using various PoW algorithms on my LAN for my buddies and I to mine/learn from. We ultimately want to go the distance of deploying an altcoin to the world, writing the ...
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How much computing power is required to bruteforce a Litecoin private key in reasonable time?

Say I want to break a Litecoin private key having the public key using brute force. How much computing power is required for that? Does any hardware exist which can find a matching private key in, say,...
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What stops people attacking my new coin?

Say I just made a new altcoin. I mined it for a few days at some reasanoble difficulty - 2000 for example. I got to the 10 000th block and I am happy with my premine and network. Then, an attacker ...
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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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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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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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What exactly is selfish mining?

What is a selfish mining attack MonaCoin suffered from?
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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 ...