Cryptocurrency Blockchains Don’t Need to Be Energy Intensive

How is it decentralized? Anyone can create an independent codebase that implements the protocol. Anyone can review the code and raise the alarm to the community if the checkpoint isn't correct. Ideally there would be a number of independent implementations of the software, each with many devs and numerous reviewers. In addition to that, the previous version of the software could be used to automatically validate that the new software contains a checkpoint that matches the longest chain as seen by that software - and again, it can raise an alarm to the user if it doesn't match, who can alert the community.

Any change in bitcoin works like this. Changes are discussed, implemented, and reviewed by hundreds or thousands of people. Users need to find the correct software in some way. Generally they would use the internet to find the right software, hopefully cross checking multiple sources. They might ask their friends what software to run. Etc. But there is no math to find the right software - each person has to use their social network (and the internet) to figure out which software is "Bitcoin". Once they download the software, it can do the rest.

The same is true for a piece of software with a hardcoded checkpoint. There is no central source for the checkpoint. Everyone who is currently part of the network can validate that the checkpoint is correct. Many people will actually do it. It would be so easy to validate that it could be automatically reviewed by people's software (unlike most other codebase changes).

So in what way would a PoS checkpoint be different than bitcoin? As I've shown above, the checkpoint itself is just another piece of the code like any other code change. The difference is that the checkpoint would be necessary to do at some regular frequency (say once a year). By contrast, you could imagine a future where the core Bitcoin software has been frozen and has not changed for years - decades maybe. And one could expect to go offline for 10 years and still be able to bring up their software without updating it.

A PoS system would be slightly different. Because of the issues around short-range and long-range revisions, people who have been offline long enough should at very least download a new checkpoint (even if the rest of the software remains the same). The new checkpoint a user downloads should be recent enough that the chances of a short-range revision attack (eg a history attack) with sufficient accumulated minting power (or whatever your preferred alternative term is for "accumulated difficulty") is sufficiently unlikely. One new checkpoint per year would ensure that a user downloading the latest checkpoint is downloading a checkpoint no farther in the past than 1 year. This would require that a sufficient number of devs and reviewers get together to review and validate the released checkpoint to make the release sufficiently decentralized. This could realistically be structured so software checks this automatically and raises an alarm to the user if the new checkpoint doesn't match or if too much time goes by without a new checkpoint being released. Millions of people could realistically participate in that - anyone that runs a full node. Even anyone that runs a light node.

Furthermore, when a user does download a checkpoint, some users are going to be careless and download some malicious checkpoint. If they do, but they have honest software, the software can ask their connections if the new checkpoint matches up with them. If it doesn't, it can again raise an alarm to the user.

For a person with an old version of the software to get a malicious checkpoint without an automatic alarm being raised, they would have to either have a virus that changed the code of the software (at which point any software PoS or PoW is vulnerable), or they would have to be eclipsed by the attacker (connected to only attacker nodes) and the attacker must also have a way to sign the release (of the checkpoint) with the authors' signatures (which the software should also automatically check) and the attacker must have accumulated enough minting power (eg in old keys bought from people who have drained those addresses already) since the software last left the chain. The attacker can't simply create a brand new chain with a different genesis block - the software would raise an alarm about that.

For a new entrant to the system, there is a higher risk, but it is no higher than with Bitcoin. The new entrant must find and install the right software somehow, on a machine that isn't compromised. This wouldn't be different for PoS.

In summary:

A. Users who have been connected to the network all along can't be tricked by any kind of history attack.

B. Users who are newly connecting to the network simply need to download the correct software, as they need to do with bitcoin.

C. Users who have been connected to the network for a time, but left for a period of time, just need to (manually) download and (automatically) verify a checkpoint.

Item C is situtation that differs most from current Bitcoin. There is some additional possibility for an attack there, but it would still be extraordinarily difficult to pull off. In Bitcoin, there is no need to download any new data, and so there is no equivalent attack vector similar to tricking the user into accepting an invalid checkpoint. However, this attack would be very difficult (eclipse, key theft), cost a lot (buying old addresses with no coins currently in them), and has a pretty limited reward potential (only the possibility of attacking returning and new entrants they can eclipse). So yes, it is a trade off. I think its a good trade off to buy higher security against a 51% attack and lower fees.

Does this make it clearer how checkpoints can be decentralized?

Okay, my apologies, I did respond a bit too glibly there.

> There is not a problem with shipping hydrogen from ghost cities in China.

There is the same problem with this that exists with many energy storage solutions: often the storage creates more carbon usage and other environmental effects than simply burning fossil fuels closer to the location where the energy is needed.

> Neither is there a problem with running datacenters that we need for other purposes than Bitcoin.

There are a bunch of reasons all the FAANG data centers are near population centers, but the two ones that are most obvious to me are:

1. Internet infrastructure is near population centers, because the people in population centers are the ones the internet it intended to connect to. If you want to hook into the backbone of the internet, you have to be located near the backbone of the internet. This is necessary for latency.

2. Data centers require technical maintenance, and technical workers capable of doing that maintenance tend to live in population centers.

> We are currently failing at combating climate change; but to have a hope of avoiding the worst case scenarios, fossils need to be replaced with renewables at an unprecedented scale. Not only current electricity use, but also energy used in transportation. It's a huge undertaking, where you need to ramp as quickly as you can in every way you can.

You're preaching to the choir here.

> The train is starting to finally move now, and in a few years, investment into renewables will not be the limiting factor. The limiting factor is how quickly it is possible to construct. Since the limiting factor is not investment; every kwh spent on Bitcoin is a kwh lost to combating climate change.

This is where we disagree, I think. There's a lot of limiting factors. Even if there's massive investment into renewables, there can always be more money and more efficient use of the money you have. One of the biggest inefficiencies of renewables is that they tend to be time-bound: as you probably know, wind produces the most at night, and solar produces exclusively during the day, and neither production cycle perfectly matches with the energy usage cycle.

(As you probably know), two popular areas of exploration here are storage and changing usage:

1. Every major storage solution either doesn't work yet, or is horribly inefficient in some way. Batteries are inefficient in output/input, and have downsides in terms of metal pollutants and disposal of retired batteries even when producing the batteries isn't the limiting factor. Gravitational storage requires huge amounts of space. Thermal storage simply doesn't work at scale yet.

2. Changing usage, i.e. running networked hot water heaters when other forms of usage are low, is a promising area of development, but so far the improvements in efficiency are very modest.

A third solution which I think you're maybe underestimating, is to simply produce more energy, and use the excess production at low usage times to mine bitcoin. The profits from this can be used for a bunch of purposes, for example to reduce the cost of renewable energy to consumers (thereby increasing adoption) or to build more renewable energy.

I'll add that while nuclear energy is not technically a renewable resource, it can be part of a strategy for reducing greenhouse gas emissions, which is arguably the most important aspect of renewables. Nuclear power solves a bunch of problems that renewables don't solve, but it also has the problem of mismatch with the consumption cycle: nuclear power production isn't cyclical like solar/wind, it's not adaptable: it's extremely expensive to spin up and down generation: there have been a bunch of times in Germany where it was cheaper for nuclear power plants to pay consumers to take their excess power than to spin down generation. Bitcoin mining has the potential to power consumption for nuclear power plants as well, which could greatly decrease the cost of running nuclear power.