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A Sybil attack is an attack where a single adversary is controlling multiple nodes on a network. It is unknown to the network that the nodes are controlled by the same adversarial entity. For example, an adversary can spawn up multiple computers, virtual machines, and IP addresses. They can create multiple accounts with different usernames and e-mail ...


10

An eclipse attack is when most (if not all) of your peers are malicious and they basically prevent you from being well-connected to the network to obtain information about transactions you're interested in. An eclipse attack is particular useful when a payer has sent some bitcoins to you in some transaction, then decides to also doublespend the same bitcoins....


6

Your understanding is correct. What you describe is known as a Sybil attack, here essentially the p2p version of a man-in-the-middle attack. In general, Bitcoin requires very little trust, as each peer can check whether new information adds up with the information that was previously gathered. The attacker could use this constellation to relay a transaction ...


4

They can lie to you about the filters, yes. However due to the filters being deterministic you can query other nodes for the hashes of their filters to gauge relative correctness. You can also use a watchtower like service to give a trusted set of the filters in some cases. The original design document includes an extension for committing to these filters ...


3

When you are buying servers you can order multiple IP per one server, typically in the same /8 or /16 subnet. So 1 server can serve as 100 or even 1000 Bitcoin nodes. Ordering lots of IPs in lots of different /16 subnets is rarely possible for the same server. Hence this change makes it harder/more expensive to launch 1000's of rogue Bitcoin nodes - you ...


3

PoW does not detect sybil attacks, it prevents them. Sybil, or sockpuppet, attack means that an attacker can spawn a large number of nodes which they control. If your full node suddenly finds itself connected to fake nodes spawned by an attacker which claim that difficulty of the block they are sending you is much less than it was upto now, your node will ...


3

Low-latency transmissions over Tor can be defeated with a timing attack if you're connected to several of the attacker's nodes and the attacker is watching your transmissions at your ISP. The attacker can relay only blocks that he/she creates, putting you on a Bitcoin fork (separate from the main chain). After that you would be open to double-spending ...


3

Not true. You have funds locked into a multisig wallet with party A, B and C. There's nothing to Sybil there: the funds have been transferred and only you and them have keys. Then you want to transfer money to G. None of your parties has a direct link to G, but C has links to D, E and F. And G is advertised as having a link to D. So C relays your money to ...


3

Proof of work is what makes Sybil attacks very difficult. Put simply, you trust the chain with the most proof-of-work on it. This cannot easily be faked (at least without significant mining power). It is possible that all the peers you happen to connect to give you false information, but at any time, if you have even one peer that tells the truth, this can ...


3

That sort of attack sounds definitely doable. But it's important to take into consideration the cost of this type of attack versus the cost of the thing that you're actually stealing (double-spending): If you're buying something expensive, the vendor will most likely require you to wait at least 2-3 confirmations, defeating the possibility for this type of ...


2

Most nodes these days do not mine at all, nor do they care who exactly is contributing hashpower to the network. Proof of work does not prevent a sybil attack from occurring, rather the required work to create a block makes it costly for a successful sybil attacker to feed the victim a tailored chain-tip. Unless uses immense hashpower, they can at best hand ...


2

would it be possible for the full node serving this request to attack the Neutrino node by providing a fake block filter that omits certain transactions? Yes. Indeed, the protocol actually specifies that data carrier outputs (OP_RETURN outputs) are always excluded from the filter. Do block filters include a mechanism that enables the thin client to ...


1

But what if all the eight nodes to whom a given node send the transaction are malicious/faulty? And all of them change the message in the original transaction. Wouldn't it allow for wrong transaction to get merged in the blockchain network? Transactions have signatures that sign the whole transaction (except signatures. Signatures are added after the ...


1

A sybil attack is prevented by using proof of work. Overwhelming the network with nodes cannot substitute for the hash power required to create the proof of work that must be presented in order to get the network to accept a new block. An eclipse attack is more difficult to prevent: Bitcoin Core only makes an outbound connection to one IP address per /...


1

Definate yes. The Sybil attack in computer security is an attack wherein a reputation system is subverted by forging identities in peer-to-peer networks. If nodes are required to proove their identity before they can join the network, just like in permissioned or private blockchains, then they will not be able to forge the identities.


1

In a sybil attack, the attacker impersonates multiple identities. In an eclipse attack, the attacker eclipses a victim from the network. That means the attacker basically controls which information the victim is able to send to the network and vice versa. I would therefore say that a sybil attack is what an adversary uses in order to perform an eclipse ...


1

Can I call such intentional easy-mining a Sybil attack? No. Because mining is a memory-less process, it is quite possible that subsequent blocks be found while the mempool is empty. Furthermore, the idea that verifying transactions takes away mining resources is moot since the SHA256 hashing is typically done on specialised hardware that can't do anymore ...


1

A Sybil attack is based on spawning a large number of instances to either isolate the attacked from other nodes, or to fake support for something. Proof of work requires expenditure of irretrievable resources to perform. Proof of work cannot be faked by spinning up more instances of the software, the energy actually has to be spent. In that sense PoW ...


1

I run simplecoin.cz|sk|pl|eu bitcoin exchange. We use different wallets and we made 10k+ transactions. We lost some bitcoins. Most of it was human errors. Some bitcoins were lost when transactions took days to confirm during network flooding. We encountered some double spend transactions (which did not confirm) On other hand we never lost bitcoins when ...


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