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Two questions: 1. Do the attackers (users who abuse this), modify all transactions they see or do they target those transactions that only involve their wallet

Two questions: 1. Do the attackers (users who abuse this), modify all transactions they see or do they target those transactions that only involve their wallet? 2. Even given the relative ease an attacker would have with modifying a transaction, that transaction still needs to be accepted by the majority otherwise their modification is ignored. So given 2 transactions for the same bitcoin transfer, I would guess that 50% of the time their transaction is accepted. I guess that the attacker could modify the transaction, for example, 4 times and then it's an 80% chance that one of their modification is accepted (4 out of 5). Do I have that right? This was a good article, I enjoyed it's breakdown with examples.

patio11 13y ago
1) Someone appears to be modifying "a large portion of all transactions." 2) You don't have to make it to a majority, you only have to propagate your transaction to the miner who wins the next block prior to the original broadcaster propagating their transaction to miner of the next block. This is really easy to arrange in a P2P network by, e.g., controlling more nodes than the original party or by e.g. modifying the standard Bitcoin client to not sleep between attempts to propagate transactions or by e.g. communicating preferentially with nodes known to be controlled by or "close to" miners and not bothering to propagate to the 99.X% of nodes which are not. If you control thousands of nodes, which you can trivially do ("rent a botnet"), you will ROFLstomp the propagation capabilities of most people originating transactions. The ease of creating extra nodes is why Satoshi designed Bitcoin as "One CPU one vote" (for a transaction's correctness) rather than "One IP one vote." Unfortunately, it appears that Satoshi did not anticipate that the transaction hash is, effectively, the latter. That wouldn't be problematic except systems which interface with Bitcoin frequently rely on the transaction hash being stable but it is, in effect, written on water for the first hour or so.
- lockes5hadow 13y ago
  Satoshi did anticipate that DDoS would be a major problem for BitCoin, which is essentially what this is.

patio11 13y ago

1) Someone appears to be modifying "a large portion of all transactions." 2) You don't have to make it to a majority, you only have to propagate your transaction to the miner who wins the next block prior to the original broadcaster propagating their transaction to miner of the next block. This is really easy to arrange in a P2P network by, e.g., controlling more nodes than the original party or by e.g. modifying the standard Bitcoin client to not sleep between attempts to propagate transactions or by e.g. communicating preferentially with nodes known to be controlled by or "close to" miners and not bothering to propagate to the 99.X% of nodes which are not. If you control thousands of nodes, which you can trivially do ("rent a botnet"), you will ROFLstomp the propagation capabilities of most people originating transactions. The ease of creating extra nodes is why Satoshi designed Bitcoin as "One CPU one vote" (for a transaction's correctness) rather than "One IP one vote." Unfortunately, it appears that Satoshi did not anticipate that the transaction hash is, effectively, the latter. That wouldn't be problematic except systems which interface with Bitcoin frequently rely on the transaction hash being stable but it is, in effect, written on water for the first hour or so.

lockes5hadow 13y ago
Satoshi did anticipate that DDoS would be a major problem for BitCoin, which is essentially what this is.