Topic: Why is there a maximum target? (Read 1562 times)
It would be trivial to switch the network from 256 bit hashes to 512 bit hashes. I haven't checked the math, but I think that we'd run out of theoretical computing power in the universe before we needed to.
I think we were talking about the time to get to difficulty 1 from "difficulty" 1/maxtarget.
Answer: 112 retargets, or 225792 blocks, or 11289600 bitcoins generated.
I guess I can see the reason for a maxtarget. Though I do kind of wish the convention were to call the minimum difficulty "4.295 Ghash/block" rather than "1".
Answer: 112 retargets, or 225792 blocks, or 11289600 bitcoins generated.
I guess I can see the reason for a maxtarget. Though I do kind of wish the convention were to call the minimum difficulty "4.295 Ghash/block" rather than "1".
I can't imagine the major network issue that would cause difficulty to drop anywhere close to 1. Any modern GPU can easily do that in far less than 10 minutes (more like less than 10 seconds).
what is the 4x rule?
The difficulty cannot change by more than a factor of four, either up nor down, in any one re-targeting. This is to limit the damage of a possible attack vector that has never been attempted. The attack involves a major hasher with much more power than the whole of the network coming in, and rather than attack the blockchain as in the double-spend attack, he simply hashes honestly with abandon up until the next retarget and then shuts his cluster off. The result being that, without the factor-of-four rule, the period of time between blocks could be stretched to an unreasonable interval. With the Fo4 rule, this attack would require that the attacker be willing to hash through several retargets in a row; otherwise his attack would be limited to stretching the interval to about 40 minutes, which would be inconvient but not detrimental to the system. The rule is probably not needed anymore, as there isn't likely any single entity left on Earth with the power to outhash the running network by more than 4 times anyway.
what is the 4x rule?
Difficulty can rise maximum 4 times or drop to 1/4 of the previous value during difficulty retarget.
what is the 4x rule?
With the 4x rule, wouldn't it take quite a few retargets before the target was properly adjusted?
The 4x rule was not present in the first several months. It was added as a security defense later. Even so, this would not have had a large impact upon the max target.
With the 4x rule, wouldn't it take quite a few retargets before the target was properly adjusted?
I'd guess satoshi chose a maximum target to allow for a. that he didnt get the first 2016 blocks so easily, as that might be looked at even worse than the whole scam stuff now. and b. if there is a major network issue at least there is still some minimum security.
Yes, that's part of it. Kept it too difficult for one, or even a few, average desktops from reaching 10 minutes between blocks. Partly as a show of faith that others were desired.
Also, setting a max target also creates the metric that we call the difficulty. The difficulty number is an estimate of how many times more difficult the target is to achieve statisticly as compared to the minimum difficulty of 1, which is defined as the max target number. Just having the target doesn't help human beings wrap our heads around the concept, but the difficulty provides a relative metric that humans can get used to.
I'd guess satoshi chose a maximum target to allow for a. that he didnt get the first 2016 blocks so easily, as that might be looked at even worse than the whole scam stuff now. and b. if there is a major network issue at least there is still some minimum security.
Ah.... sorry.
They didn't really answer the question, though.
They didn't really answer the question, though.
From a couple days ago: http://forum.bitcoin.org/index.php?topic=8928.0
Or more accurately, why isn't the maximum target 2^256 - 1? The issue of excessively fast block generation would have resolved itself within less than a second after the first client was run. Or the initial difficulty could have just been set to 1,000,000,000.
The scaled-down shares-per-block difficulty may be easier on the eyes, but its interpretation is kind of opaque. Quoting difficulty in Ghash/block at least means something.
The scaled-down shares-per-block difficulty may be easier on the eyes, but its interpretation is kind of opaque. Quoting difficulty in Ghash/block at least means something.
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