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How Blockchain Works

blockchain.mit.edu

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Re: How Blockchain Works

#131

Post by dlubarov »

abraham_lincoln wrote: post #106
p4bl0 wrote: post #69

This is a very good and clear explanation of how bitcoin type blockchains work. It could easily have been made simpler and more general at the same time by omitting the proof of work aspect, which is not even discussed actually. The "begin with four zeros" rule is completely arbitrary, it could be any prefix of any length depending on the necessary amount of work that you want, including zero. And with an empty prefi…

Is it necessary to be based on the prefix, or can it be implemented by pattern, for instance, every even byte is zero, or the 4 bytes after the first 3 bytes must be all 7s, etc? Is it simply brute-forcing hashes, looking for matching patterns that are not yet known?

In practice Bitcoin treats SHA-256 outputs as integers, and requires them to be under a certain limit, based on the current difficulty.

That way we can make small adjustments to the difficulty. If we actually used a rule like "this many zeros in hex", the difficulty bumps would have to be rather large.

Re: How Blockchain Works

#132

Post by lmpostor »

abraham_lincoln wrote: post #106
p4bl0 wrote: post #69

This is a very good and clear explanation of how bitcoin type blockchains work. It could easily have been made simpler and more general at the same time by omitting the proof of work aspect, which is not even discussed actually. The "begin with four zeros" rule is completely arbitrary, it could be any prefix of any length depending on the necessary amount of work that you want, including zero. And with an empty prefi…

Is it necessary to be based on the prefix, or can it be implemented by pattern, for instance, every even byte is zero, or the 4 bytes after the first 3 bytes must be all 7s, etc? Is it simply brute-forcing hashes, looking for matching patterns that are not yet known?

I don't see what prevents you from adding complexity.

And yeah, but it also requires valid transactions if you want to collect fees, as well as the knowledge of the valid previous block.

Re: How Blockchain Works

#134

Post by dlubarov »

TheDong wrote: post #129
yarrel wrote: post #88

Earlier quoted context omitted.

Trust. If you are a small producer and you send a shipment of your widgets to Wal Mart, and Wal Mart then say "what widgets?", the efficiency of their SQL Server installation isn't a benefit that will bring you much comfort. If you are a small producer and you send a shipment of your widgets to Wal Mart with little rfid stickers on tracked by a blockchain system that you, the shipping company, border security, Wal Ma…

We have a shipment tracking system now without blockchain. > little rfid stickers on them ... If the problem you're trying to solve is the one you say, you might as well just run a few servers across different organizations / companies which replicate between themselves, like certificate transparency does, or like the gpg web of trust does... which isn't a blockchain because it's vastly more efficient.

A CT-style system could work for supply chains, but let's say for the sake of convenience, we wanted to use some shared storage system rather than building a new system for supply chains only.

We could have one big CT-style log system host many applications, but as the number of participants grew, we would want some mechanism to prevent spam. Even if there was no outright spam, some users would generate a large volume of logs with questionable utility, and humans would need to get together to decide if those users should be blacklisted or what.

Ethereum gives us spam control via gas costs. I can't imagine a good, low-maintenance solution that doesn't resemble some cryptocurrency. Paying fees from a ledger isn't absolutely necessary -- we could proof of work to discourage spam, like iota -- but charging fees in a ledger seems like the better solution, and isn't that much more complicated.

Re: How Blockchain Works

#135

Post by UncleMeat »

thedancollins wrote: post #114
prostoalex wrote: post #91

Earlier quoted context omitted.

> it is about the speed of transactability As somebody pointed out https://news.ycombinator.com/item?id=18076542 high transaction throughput is not exactly the killer feature of modern-day blockchains.

Well ok, buit I was talking about transactability - not throughput. I have stated numerous times that the tech struggles to be viable at scale. On Bitcoin's blockchain you can transact and settle in 10 minutes. That beats 2 to 3 days all day long in a fiat-based system.

Why does this matter? What can I do with ten minute settlements that I can't do with my debit card?

Re: How Blockchain Works

#136

Post by hef19898 »

abraham_lincoln wrote: post #115
hef19898 wrote: post #78

Earlier quoted context omitted.

Which is exactly the point I still try to get my head around when it comes to supply chains. First, for blockchain to work you need trustable sources. Problem is, when the aource is trustworthy, what added benefit comes from a blockchain? Second, having a, theoretically uninterrupted blockchain from the first raw material to, say, a car would provide way to much insight into supply chains. I pretty sure companies do…

Have you worked in manufacturing with ERP systems and BoM transactions? I could see how this would be useful for medical device manufacturing, especially something like a pacemaker.

Indeed I did. Thing is, I see how blockchain could help existing processes. I just don't see the revolution yet. Which puzzles me, since on the one side I see the potential but on the other hand I still fail to see a real use case. And that introgues me quite a lot.

Re: How Blockchain Works

#137

Post by UncleMeat »

neospice wrote: post #84
vec wrote: post #63

Earlier quoted context omitted.

Yes, but if you have a mechanism (either technical or institutional) that you trust to attach real-world goods to your blockchain in a sufficiently correct and tamper-resistant manner, why not just let that mechanism manage your ledger directly and skip the blockchain entirely?

Those seem like two separate problems to me. The oracle reliably reports to the blockchain while the blockchain ensures that the historical record is tamper-proof.

But why can you trust the oracle to report correctly but not to maintain the record?

Re: How Blockchain Works

#138

Post by UncleMeat »

sparkzilla wrote: post #55
this_user wrote: post #26

Earlier quoted context omitted.

A blockchain is just a type of data structure. I have yet to see any use case, outside of building crypto currencies, that could not be realised without it. The problem is not that the technology did not exist before, the problem is that people and organisations were slow or unwilling to adopt it. But that is not the type of issue that will be solved by introducing new technology, and almost all blockchain advocates…

My company aims to convert all the world's news into data. Please tell me another technology that will allow us to build a decentralised, failure-tolerant, censorship- and tamper-resistant archive of that data, that allows anyone to add data, and have it verified without a central authority, and that anyone can use to create news applications.

Anybody can already create news applications. Just put up a blog.

Re: How Blockchain Works

#139

Post by UncleMeat »

sparkzilla wrote: post #90
the_snooze wrote: post #75

Earlier quoted context omitted.

And what exactly are you verifying?

In its most basic form, we verify that data extracted from news articles matches what has been reported. So, when we extract the data "Trump, Speech, Alabama, Immigration" from an article, then it has to match the reporting in that original source, which may have included a sentence like, "Trump gives a speech in Alabama about immigration". To avoid the verification process being gamed we split up the data and send p…

So what happens when your verifier fails? Do you prevent the publication of the text? That hardly seems decentralized.

Asking humans to review the accuracy of all published text will never scale.

Re: How Blockchain Works

#140

Post by sparkzilla »

UncleMeat wrote: post #139
sparkzilla wrote: post #90

Earlier quoted context omitted.

In its most basic form, we verify that data extracted from news articles matches what has been reported. So, when we extract the data "Trump, Speech, Alabama, Immigration" from an article, then it has to match the reporting in that original source, which may have included a sentence like, "Trump gives a speech in Alabama about immigration". To avoid the verification process being gamed we split up the data and send p…

So what happens when your verifier fails? Do you prevent the publication of the text? That hardly seems decentralized. Asking humans to review the accuracy of all published text will never scale.

The amount of verification required depends on the data. Simple data, such as sports results -- coming from high-quality sources doesn't require much verification, and can be automated. More complex data requires human verification, but that will gradually be replaced by distributed machine learning.
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