Quote from: smooth on October 06, 2014, 11:10:05 AM

Quote from: TheFascistMind on October 06, 2014, 10:30:25 AM

Clearly you see now the potential problem in Cryptonote with the 20% discard rule. It enables the secret chain to hide a bunch of blocks without causing a rise in difficulty.

No, it isn't clear. You can't really hide any blocks just by making them outliers because the outliers starting at the most recent end of the adjustment window (for example if you timestamped into the future) still have to slide through the middle before exiting the window on the other end. So you can only defer them from contributing to the adjustment for a little while, but eventually they do get counted (similar in effect to a window-based adjustment like Bitcoin). The outliers at the farthest-in-the-past end might be able to slide off without ever being counted, but even if you could figure out how to drop blocks there right away, that would only increase difficulty, not decrease it. There still might be a flaw, but we have to do better than that to graduate from FUD.

Not printing the timestamps far into the future, rather the statistics of the variations in gaps between the timestamps. You could bunch some them closer at a faster rate in time so they are deemed statistical outliers (I presume, haven't seen the math presented in any white paper), so they don't get counted in the computation of the difficulty.

But even this won't matter if the total difficulty of the forks is compared as the sum of modular additive inverses of the block hashes, then there is no way the secret fork can be longer (other than diluting the honest fork's hashrate with DDoS or orphans via selfish mining or block propagation interference).

Thus I rescind my opinion that BCX is attacking with such a secret fork. He could possibly attack with some other vulnerability (such as my idea about messing with the ROI of miners thus driving network hashrate down), but not this one.

Edit: the ideas about messing with the ROI of the miners remain. If you can push the hashrate up higher than it should be then prevent or delay the readjustment and also selfish mine, you can amplify the ROI pain on the honest miners over selfish mining alone.