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are you talking about a double-spend attack?

by VMG 13y ago

jedunnigan 13y ago
Sounds like a 51% attack. But to the subject of the thread: Baidu should be using a Hierarchical Deterministic pub/priv key tree. [1] Increases their financial privacy 10-fold. [1] https://en.bitcoin.it/wiki/BIP_0032 https://en.bitcoin.it/wiki/BIP_0032
- VMG 13y ago
  Right, I also meant 51% attack. I'm not sure if he also meant it, because the attack described by betterunix isn't quite what a 51% attack is about.
  - jedunnigan 13y ago
    >that it is an expensive attack, in the low billions of dollars to pull off. Preventing that attack would require half the computing resources in the world to be devoted to Bitcoin at all times. That sounds like a 51% attack, although the 'half of all computing resources' is off the mark. The OP is right here, it is a very feasible attack at the moment, which is why some are concerned that SHA256 is too specializable (ASICs) which means that a dedicated adversary with access to chip manufacturing could print a few wafers and own the network at low cost. There aren't many attacks on the network that require that kind of computational power. I could see the NSA running a large portion of nodes to de-anonymize users, but beyond that I don't know what else it could be. A double spend attack wouldn't require much effort (right now at least, that will change) [1]. [1]http://www.tik.ee.ethz.ch/file/848064fa2e80f88a57aef43d7d5956c6/P2P2013_093.pdf http://www.tik.ee.ethz.ch/file/848064fa2e80f88a57aef43d7d595... [1a]http://www.tik.ee.ethz.ch/file/49318d3f56c1d525aabf7fda78b23fc0/P2P2013_041.pdf http://www.tik.ee.ethz.ch/file/49318d3f56c1d525aabf7fda78b23... [1b] We will see some of these changes in bitcoind .9 (so says Gavin)
    - betterunix 13y ago
      "'half of all computing resources' is off the mark." I suppose that I could have stated it somewhat better by saying this: half the energy output of the planet needs to be devoted to the most energy-efficient Bitcoin mining hardware possible to guarantee that no attack is occurring, and only if that hardware is being used by honest miners and not an attacker. Of course, in practice no attacker will amass anything close to that (it would leave no power left for anything other than Bitcoin), but in practice the world will never devote anything close to half its energy resources to Bitcoin. Even generous estimates of what the world's energy economy could devote to Bitcoin leave an awful lot of room for an attack, and while the attack might not make economic sense in terms of the market value of Bitcoin or the mining payoff, it might be part of some broader plot (perhaps a war against a country where Bitcoin is popular and widely relied on). "I could see the NSA running a large portion of nodes to de-anonymize users" Why would they bother? Bitcoin transactions are broadcast to the entire Bitcoin network anyway. All the NSA would need is a handful of desktops and some auxiliary information about which wallets belong to which users (perhaps gather by watching Bitcoin exchanges). Bitcoin makes no anonymity guarantees at all.
      - jedunnigan 13y ago
        > Even generous estimates of what the world's energy economy could devote to Bitcoin leave an awful lot of room for an attack, and while the attack might not make economic sense in terms of the market value of Bitcoin or the mining payoff, it might be part of some broader plot... I won't refute this, because you are right. I was just speaking in more manageable/realistic terms. >Why would they bother? Bitcoin transactions are broadcast to the entire Bitcoin network anyway. All the NSA would need is a handful of desktops and some auxiliary information about which wallets belong to which users (perhaps gather by watching Bitcoin exchanges). Bitcoin makes no anonymity guarantees at all. Bitcoin is not anonymous, correct. That doesn't mean that it is easy to break the barrier from pseudonymous - > known identity. Let's say there is a clever participant in the network, Satoshi, who is under investigation by the NSA. The NSA knows they will be sending 10btc to their cohort at address xyz. Satoshi is smart, he is not going to use an exchange to get his coins. Maybe he mined them. Maybe he got them in a f2f transaction. This leaves few options to find out information about Satoshi. However, if the NSA ran a sufficient number of nodes, they could easily determine the first node to propagate a transaction. This would be Satoshi's IP address. That is why they would do this.
- clarkm 13y ago
  Yep, everyone should be using HD Wallets. Not only are they essential for one's own privacy, but they are also good for preserving overall network privacy. Plus, they make accounting easier.

are you talking about a double-spend attack?

by VMG 13y ago

are you talking about a double-spend attack?

Sounds like a 51% attack. But to the subject of the thread: Baidu should be using a Hierarchical Deterministic pub/priv key tree. [1] Increases their financial privacy 10-fold. [1] https://en.bitcoin.it/wiki/BIP_0032 https://en.bitcoin.it/wiki/BIP_0032

VMG 13y ago
Right, I also meant 51% attack. I'm not sure if he also meant it, because the attack described by betterunix isn't quite what a 51% attack is about.
- jedunnigan 13y ago
  >that it is an expensive attack, in the low billions of dollars to pull off. Preventing that attack would require half the computing resources in the world to be devoted to Bitcoin at all times. That sounds like a 51% attack, although the 'half of all computing resources' is off the mark. The OP is right here, it is a very feasible attack at the moment, which is why some are concerned that SHA256 is too specializable (ASICs) which means that a dedicated adversary with access to chip manufacturing could print a few wafers and own the network at low cost. There aren't many attacks on the network that require that kind of computational power. I could see the NSA running a large portion of nodes to de-anonymize users, but beyond that I don't know what else it could be. A double spend attack wouldn't require much effort (right now at least, that will change) [1]. [1]http://www.tik.ee.ethz.ch/file/848064fa2e80f88a57aef43d7d5956c6/P2P2013_093.pdf http://www.tik.ee.ethz.ch/file/848064fa2e80f88a57aef43d7d595... [1a]http://www.tik.ee.ethz.ch/file/49318d3f56c1d525aabf7fda78b23fc0/P2P2013_041.pdf http://www.tik.ee.ethz.ch/file/49318d3f56c1d525aabf7fda78b23... [1b] We will see some of these changes in bitcoind .9 (so says Gavin)
  - betterunix 13y ago
    "'half of all computing resources' is off the mark." I suppose that I could have stated it somewhat better by saying this: half the energy output of the planet needs to be devoted to the most energy-efficient Bitcoin mining hardware possible to guarantee that no attack is occurring, and only if that hardware is being used by honest miners and not an attacker. Of course, in practice no attacker will amass anything close to that (it would leave no power left for anything other than Bitcoin), but in practice the world will never devote anything close to half its energy resources to Bitcoin. Even generous estimates of what the world's energy economy could devote to Bitcoin leave an awful lot of room for an attack, and while the attack might not make economic sense in terms of the market value of Bitcoin or the mining payoff, it might be part of some broader plot (perhaps a war against a country where Bitcoin is popular and widely relied on). "I could see the NSA running a large portion of nodes to de-anonymize users" Why would they bother? Bitcoin transactions are broadcast to the entire Bitcoin network anyway. All the NSA would need is a handful of desktops and some auxiliary information about which wallets belong to which users (perhaps gather by watching Bitcoin exchanges). Bitcoin makes no anonymity guarantees at all.
    - jedunnigan 13y ago
      > Even generous estimates of what the world's energy economy could devote to Bitcoin leave an awful lot of room for an attack, and while the attack might not make economic sense in terms of the market value of Bitcoin or the mining payoff, it might be part of some broader plot... I won't refute this, because you are right. I was just speaking in more manageable/realistic terms. >Why would they bother? Bitcoin transactions are broadcast to the entire Bitcoin network anyway. All the NSA would need is a handful of desktops and some auxiliary information about which wallets belong to which users (perhaps gather by watching Bitcoin exchanges). Bitcoin makes no anonymity guarantees at all. Bitcoin is not anonymous, correct. That doesn't mean that it is easy to break the barrier from pseudonymous - > known identity. Let's say there is a clever participant in the network, Satoshi, who is under investigation by the NSA. The NSA knows they will be sending 10btc to their cohort at address xyz. Satoshi is smart, he is not going to use an exchange to get his coins. Maybe he mined them. Maybe he got them in a f2f transaction. This leaves few options to find out information about Satoshi. However, if the NSA ran a sufficient number of nodes, they could easily determine the first node to propagate a transaction. This would be Satoshi's IP address. That is why they would do this.
clarkm 13y ago
Yep, everyone should be using HD Wallets. Not only are they essential for one's own privacy, but they are also good for preserving overall network privacy. Plus, they make accounting easier.