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Your first statement is true only if the difficulty on both chains are equal. Lets assume chain A and chain B have the same hash power across their respective
by oillio 13y ago
Your first statement is true only if the difficulty on both chains are equal.
Lets assume chain A and chain B have the same hash power across their respective networks. Chain A has a block every 10 minutes, and Chain B has a block every 1 minute. The difficulty of finding a block in Chain B will be 10x easier than Chain A. Therefore an attacker will be 10x as likely to find a block on Chain B than Chain A.
On chain A, 6 confirmations provides a certain level of security against a double-spend. To get that same amount of security on chain B, you need 60 confirmations.
Your security against double spend is equal to the total network hashing power multiplied by the time since your transaction was added to the chain. Increasing the block speed does not affect your security.
Increasing the block speed only provides a smaller measure of your security. If you are OK with 3 minutes of security at the current network hashing power, you still have to wait for the first block on chain A (up to 10 minutes). On chain B, you would be satisfied after 3 blocks (max 3 minutes).
- dragontamer 13y agohttps://news.ycombinator.com/item?id=7117592 https://news.ycombinator.com/item?id=7117592 Lets take a hypothetical look at a coin that has a 1-hour confirmation time, and compare it against Doge, BTC. Lets call it HourCoin. If you have 30% control of the mining pool, you have a 30% chance to "double-spend" anyone who accepts HourCoin after 1-hour (aka: one confirmation) If you have 30% control of the BTC mining pool, you only have a 0.07% chance of double-spending any transaction after 1-hour. (aka: 6 confirmations) If you have 30% control of the DOGE mining pool, you have a 4.23e-32 chance of double-spending a transaction after 1-hour. If you're concerned with the 50% attack, then you should favor coins with faster confirmation times. It reduces the efficacy of "near 50%" attacks.
- fragsworth 13y ago> For an organization with 45% hashing power to maliciously double-spend cross 20 confirmations, it'd have to win the coin flip 20 times, or 0.00001% of the time. That's not right. If they want to maliciously double-spend, they'd just have to get 20 blocks in less time than the rest of the network got it in, and publish their result. This is not the same as beating the network at 20 individual blocks. For instance, you can double spend by getting your 20 blocks in 19 minutes, when the rest of the network took 21 minutes. This is not the same as beating the rest of the network at all 20 blocks - some of yours may have taken longer.
- makomk 13y agoYou're technically right - the correct calculation is in section 11 of Satoshi's original paper [1], though the probability of success still reduces exponentially with the number of confirmations in the same way that dragontamer's calculation does. [1] http://bitcoin.org/bitcoin.pdf http://bitcoin.org/bitcoin.pdf
- dragontamer 13y agoThanks for the link. Binomial walk makes sense. So it isn't 2^n, but a convolution summation over n-choose-r. Yeah... I don't feel like doing the "correct" math on this one. But the concept is still correct. It is exponentially harder for the malicious user to double-spend based. It is much harder to break ten "one minute" confirmation, than one "ten minute" confirmation.
- oillio 13y agoThis is useful in practice if you are willing to accept only 1 or 2 confirmations. For retail type situations, a fast blocks are definitely better, which I touched on at the end of my post. I constantly see the argument that 6 confirmations on LTC == 6 confirmations on BTC. This is the argument the original poster was making, and this what I am arguing against.