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Can anyone read the paper? I don't understand how a minority group of colluding miners could privately mine a longest fork of the blockchain. Wouldn't this ta

Can anyone read the paper? I don't understand how a minority group of colluding miners could privately mine a longest fork of the blockchain. Wouldn't this take more than 50% hashing power?

modeless 13y ago
On average, yes. But mining is a probabilistic process. Occasionally, a minority group will get lucky and mine two blocks in quick succession. If they keep their blocks secret, then they can cause the rest of the network to waste time mining on obsolete blocks and thereby increase their effective share of the network's hash power.
- danielweber 13y ago
  Could they double-spend some coins by spending them on the public chain, and then get their chain where they didn't spend them accepted as the new public chain?
  - KingMob 13y ago
    Not effectively. Whichever chain ultimately wins still defines the outcome of "double-spent" coins, so if they tried to double-spend, one transaction would still be rejected when its chain is rejected by the mining community. If I understand correctly, the only way to do this would be to get a private chain longer than the typical number of accepted confirmations, which is currently 6 for most merchants. In this method, you spend the coins, wait for 6 confirmations, the merchant ships the product, and then you reveal a longer chain where those coins were never spent. However, getting a chain advantage of that length is extremely unlikely without a massive fraction of the network power. The attack described is for pools where they lack a majority of the processing power, but still have enough power to occasionally make chains at least a couple blocks longer than the rest of the miners.
  - deleted 13y ago
    [deleted]
javert 13y ago
Mining a longest fork and maintaining it is probable if you have more than 50%. If you have less than 50%, there is still a chance, but eventually, the main chain will catch up. For example, even if I'm a pool with 25% of mining power, I could still occasionally find 2 blocks in a row. But I won't maintain that lead because in general, over time, for every 1 block I find, 3 other blocks will be found. It looks like this paper's technique is to take advantage of those temporary situations where one pool is lucky enough to get ahead.

Can anyone read the paper? I don't understand how a minority group of colluding miners could privately mine a longest fork of the blockchain. Wouldn't this take more than 50% hashing power?

modeless 13y ago

On average, yes. But mining is a probabilistic process. Occasionally, a minority group will get lucky and mine two blocks in quick succession. If they keep their blocks secret, then they can cause the rest of the network to waste time mining on obsolete blocks and thereby increase their effective share of the network's hash power.

danielweber 13y ago
Could they double-spend some coins by spending them on the public chain, and then get their chain where they didn't spend them accepted as the new public chain?
- KingMob 13y ago
  Not effectively. Whichever chain ultimately wins still defines the outcome of "double-spent" coins, so if they tried to double-spend, one transaction would still be rejected when its chain is rejected by the mining community. If I understand correctly, the only way to do this would be to get a private chain longer than the typical number of accepted confirmations, which is currently 6 for most merchants. In this method, you spend the coins, wait for 6 confirmations, the merchant ships the product, and then you reveal a longer chain where those coins were never spent. However, getting a chain advantage of that length is extremely unlikely without a massive fraction of the network power. The attack described is for pools where they lack a majority of the processing power, but still have enough power to occasionally make chains at least a couple blocks longer than the rest of the miners.
- deleted 13y ago
  [deleted]

javert 13y ago

Mining a longest fork and maintaining it is probable if you have more than 50%. If you have less than 50%, there is still a chance, but eventually, the main chain will catch up. For example, even if I'm a pool with 25% of mining power, I could still occasionally find 2 blocks in a row. But I won't maintain that lead because in general, over time, for every 1 block I find, 3 other blocks will be found. It looks like this paper's technique is to take advantage of those temporary situations where one pool is lucky enough to get ahead.