(I am willing to admit here I don't know enough about monero in particular to grok whether the mining blacklist thing would work on that chain. I'm pretty sure it could for BTC)
It is definitely a major flaw in Bitcoin and all other transparent blockchains.
"Trust less" however is a matter of definition. You allays need to trust "something" outside of you control like for example the majority of validator nodes or miners or those in control of the mining pools etc. and on a lower level thous in control of the internet hardware like undersea cables and thous in control or power grids etc. etc. You need to trust them all that they don't turn off the nodes or collude and disconnect the nodes form each other etc.
However you need no trust to verify that what they already did so far on the ledger/chain is correct you can locally check that and verify for yourself that the current state of the ledger is correct (sill need to trust the code ofc but you could theoretically write you own code to do the verification).
For the most part you only need trust less verification of the past/present and reasonable certainty that there will be correct forward progress. However BTC for example can not deliver that because although you can verify the past/present state you have no way to assure that you will not see a different and longer chain later on that is also verifiable and correct and thus would change "your assumed correct past state".
Well yes, and you are stretching that definition really far, if you are presenting Ripple as a "trustless" platform. They are very far from Satoshi's cypherpunk vision (which while is perhaps extreme in some ways, a lot of people really like, and most importantly, it actually works in practice, in PoW chains). Ripple's "trustlessness" is about as trustless as the SWIFT network.
> you have no way to assure that you will not see a different and longer chain later on that is also verifiable and correct and thus would change "your assumed correct past state".
Yes, you do, you wait for 6 confirmations. This has been, i fact, working in practice for all of the history of Bitcoin. This principle, in the context of the Bitcoin network has historically had less outage time than any one of the world's stock exchanges or banks.
>Yes, you do, you wait for 6 confirmations.
That exactly what I said. You can not rely on the present state even if you can validate it and "know" it's "correct" it doesn't have to be the longest correct chain. Waiting 6 blocks may be the real world workaround but it does not change that fact. Also 6 blocks is arbitrary why not 7? or 21? Longer is obviously better but there is no certainty it just gets exponentially more certain the longer you wait.
>Bitcoin network has historically had less outage time than any one of the world's stock exchanges or banks.
That's kinda a nonsense statement, the bitcoin network can not really have an outage because as long as there is one miner it technically still running. Or if large part of the network go offline it still keeps going for the rest there could be accidental forks and very long block times and what not but it can't be down. Since transaction take forever anyway because you need to wait many blocks, no one relies on it "being there" every second of the day. Its not like an stock exchange where at any second data has to be processed and any delay is "downtime". You just send your Tx into the network and it has plenty time to spread and eventually be included in the next block.
BTW the XRPL went online (completely centralized back then) in 2013 and since has never had any outages. In the early days there where some time synchronization problems which resulted in larger block times but they where still an order of magnitude shorter than bitcoins median block time.
(no doubt someone will be along in a minute to tell me that cryptocurrency mining somehow uses "spare" electricity and burning the same amount of power as a mid-sized country isn't actually a problem at all!)
0: and it is a definite article, like the internet. There by definition can't be more than one at any given time.
This is the goal we should aim for: As we're approaching the upper limit of Moore's Law, mining equipment will have a much longer lifetime and focus on reducing the cost of production could turn households and other buildings into data furnaces. It may not even be necessary for mining to be profitable - as long as there is there is a large enough ROI for users of such data furnace to cover its initial cost and eventually reduce their heating bill.
> 0: and it is a definite article, like the internet. There by definition can't be more than one at any given time.
Technically multiple chains can and do exist at any time because there is no "given time" - time is relative. Two miners at two ends of the earth may both produce a valid block at a given time (say, in UTC), but the nodes in proximity to them will receive their blocks at different times, due to distance and the fundamental speed limit of information transmission. The multiple chain conflict lasts until the next block is produced. Such conflicts could last for multiple blocks in a row, but with a probability which rapidly declines with number of blocks.
Er, no, I mean you can't have more than one (distinct) live blockchain standard; eg if you have Bitcoin and Litecoin, one of them must be using less than 50% of the available hashing capacity (because otherwise it would add up to >100%), and therefore not be secure[0].
Good point about some power use having beneficial side effects (heating) in addition to the actual work though.
0: because if it ever actually needed the security - was more valuable to attack than the majority chain - then the miners on the majority chain would have a economic incentive to attack the minority chain and gain more from attacking than they lost from undefended attacks on the majority chain.
Obviously it's possible to have two blockchains in practice, just like it's possible to have two internets in practice, but there's a constant pressure to drain applications from the minority (quasi-)singleton into the majority singleton until the minority goes defunct from lack of use.
There have even been reorg attempts that have been defended by miners that support the minority chain, making it a bit more difficult to determine how secure a chain really is.
Personally I'd rather miners use ASICs for their hash collision wankery and leave the consumer markets alone. But I'd really like to see miners cease to exist because crypto comes with a huge environmental cost and so many externalities.