Those time stamps are there for other reasons that may someday in the future be useful (like contract enforcements, or marking an anniversary, or something) It does not have any affect on the algorithms that govern the block chain.
Are you stating that timestamps aren't used to calculate the difficulty? Are you stating there are no possible manipulations of the difficulty via timestamps that could be exploited? If yes, where I can read the analysis?
Correct.
I went down this path a good while back myself. I even pestered a couple of the devs for a minute to confirm my assessment in the code.
If there is a record of that part, it would be in the IRC log, it was only a few lines. I didn't want to waste much of their time with it as it is only a matter of perception and not a technical problem needing to be fixed.
I wrote a few words about it yesterday.
https://bitcointalk.org/index.php?topic=789978.msg9039996#msg9039996
If anything, that BCX pointed to it as meaningful, is less evidence of an attack, not more.
Does XMR still throw away 20% of the timestamps which are the statistical outliers when computing the difficulty?
So thus I could mine a chain with a much higher cumulative difficulty without triggering a difficulty adjustment.
Have you analyzed this genre of attack vectors?
Yes, XMR still throws away 20% difficulty anomalies, those timestamps are not used for determining difficulty.
Yes, if <20% of the blocks were at much higher difficulty within a 720 block sliding window, it would not trigger a difficulty adjustment.
Chain contention (which would be needed for a successful TW) is based on total sum difficulty, so it would essentially be a 51% attack that is stored up and then dumped on the chain all at once at a later date causing chain contention over which fork is longer, and grabbing all the block rewards for the stored period. It is defeated by checkpoints.
If BCX is running a forked chain with >50% of the difficulty of the live chain and maintaining that for 22 days, it is a grand waste of effort.
I keep trying to posit there are other forms of difficulty attacks that can't be defeated with checkpoints. I been hinting at it for many days now.
What % of hashrate is needed for selfish mining attack?
How much can he amplify his hashrate by hiding it in the 20%?
Remember he said he needed only 20% of the hashrate. Seems obvious to me what he is doing.
Perhaps he can further amplify it by getting miners to join his pools which are gaining an edge in payouts, but I don't assume that is necessary.