Quote from: onelineproof on September 05, 2018, 04:45:50 PM

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Look, we just had a sudden 35% increase in hashpower recently (from what I read in the news), that's enough for a selfish mining attack, so to trust in the decentralization of Bitcoin mining is a bit of a shaky argument I believe, and I don't think what I am suggesting is urgent, but should carefully and smoothly rolled in, without much complication.

35% increase of total hashpower is not the same as a single miner increasing their hashpower by 35%.

Looking at Bitcoin's current hashrate distribution per pool, the proportions don't seem to have shifted much [1]. Distributed evenly, a 35% hashrate increase merely means that attacking the network via hashing power just got harder.

[1] https://www.blockchain.com/en/pools?timespan=24hours

Quote from: onelineproof on September 05, 2018, 04:45:50 PM

There have been other core developers also concerned with the decentralization of mining, and even planning for a PoW change in case a 51% attack happens. I think other technologies like sidechains and merge mining will strengthen decentralization and hashpower attack prevention in the future also.

I know too little about sidechains to give an educated opinion, but what brings you to the conclusion that merge mining helps decentralization? I'm only thinking of Namecoin right now, so I might have missed some recent development in this area.

Quote from: TeamBitmark on September 06, 2018, 09:50:09 PM

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A more interesting question for the remaining part of the network is just how badly the hash rate was affected, and how long it would take of the 10 minute average block time take to be re-established. It might be wise for bitcoin to adopt one of the more sophisticated diffalgos which were developed for alt coins suffering from wild hash-rate swings for this reason: the unexpected disappearance of substantial hash rate. Unlikely, yes, but impossible, no.

In theory, yes. In practice I think this is much harder to achieve in a robust, nearly side-effect free way than one may imagine. Prime example is the mess that was BCH's EDA. That is not to say that solving this problem is impossible. I just think that it's a harder problem than it looks -- moreso with a crypto the scale of Bitcoin.

Quote from: onelineproof on September 07, 2018, 01:39:01 PM

@Heretic says:

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If the mining reward is reduced with a drop in difficulty, Bitcoin becomes even less profitable to mine, with more and more miners leaving as block reward is further and further dynamically reduced, creating the very pool of "spare" hashing power that the difficulty-dependent-block-reward is trying to avert.

I want to revist this scenario, assuming no merge mining. First, I think a price drop will be slightly offset by the lower rate of coins being mined. Also, confirmation times will get longer: Both the time to get a block will increase and the number of confirmations needed to have enough work done on the chain so that your transaction is considered safe. The fees would likely rise and this would increase rewards to miners, especially in a fee-market dominated future. It would be nice to write this up in terms of mathematical equations to see exactly what would happen.

I've also been thinking about how the decreased currency issuance rate could absorb part of the price drop. However I think the negative price pressure would be larger for two simple reasons:

1) Historically speaking, decreased currency issuance rate (ie. halvings, in our case) took a couple months to be reflected in Bitcoin's price

2) Low confirmation times and increased fees put a lot of negative short-term price pressure that could turn into mid- to long term price pressure in case of a downward spiral

Quote from: onelineproof on September 07, 2018, 01:39:01 PM

@Heretic says:

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Anyone willing to waste their resources on mounting a 51% attack on Bitcoin will do so regardless of whether we try to tweak the incentive structure in one way or another. Assuming such an adversary exists, selfish mining or covertly aggregating (unused) reserve hashing power would be the least of our worries.

Also revisiting this...I think I should add another category of attacks that I am trying to prevent: subtle attacks that are profitable and don't significantly affect the price of Bitcoin. This could be block withholding attacks (mining pools wasting each other's resources), networking attacks (to mess with other miners' connectivity), physical attacks (like purposely selling defective hardware and for yourself mining with the good hardware). I think this is what Peter Todd was talking about in the Reddit post about "other subtle and more effective attacks", and he (and others) likely don't want to lay them all out to give attackers bad ideas. Even EMP attacks on general electric devices can be considered "subtle" as it can be done to look like just an attack on general devices, while really it is targetting an area dense with honest miners. The selfish mining attacks and collusion attacks (the other categories) can also be done quite profitably I think, but with Internet anonymity still immature, they are less practical (as Peter Todd also indicated). In general, the point of my proposal is to disincentivize miners from driving out the competition. With the same reward for a lower hashrate, it is profitable to drive out competiton (lower overall hashrate) as that gives a bigger share to the attacker, and the same reward. If someone knows other ways to achieve this goal, then please let me know. This is one simple way that I think would work.

I think the subtle attacks that Peter Todd was talking about where political attacks similar to the BCH / B2X dramas we saw in 2017. That's just my guess though.