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How Blockchain Works

blockchain.mit.edu

51–60 of 176 posts

Re: How Blockchain Works

#52

I used this blockchain demo to teach a class this weekend. Many thanks to Anders Brownworth for creating this: https://anders.com/blockchain/blockchain.html

Even the MIT URL in the source uses Anders demo -- it's that good.

Edit: Oh wow -- Anders is the author of the MIT demo. All the same stuff really.

Re: How Blockchain Works

#53
post #43

Earlier quoted context omitted.

Yeah, I'm quite skeptical of it as well. If I'm being really charitable to it, then it's a way to synchronize data between parties without relying on a trusted intermediary. That said, it's unclear what practical value that has outside of purely digital applications like cryptocurrency. When you roll it into things in the real world (e.g., supply chains, health records, etc.) then you necessarily have to trust the da…

Indeed I have conjectured multiple times that I think the only application of blockchains is in cryptocurrency. Introducing any physical asset like a yacht or a banana in Laos or a diamond in Africa really doesn't make sense: you can't literally put those physical things in the blockchain.

> you can't literally put those physical things in the blockchain

You can not otherwise too, right? A blockchain holds interactions/transactions not the data itself. Most blockchains are incredibly small in size. For example, the size of the entire Bitcoin blockchain is 215.84 GB [0].

[0] https://bitinfocharts.com

Re: How Blockchain Works

#54
post #11

Earlier quoted context omitted.

Because 'milk' is an unmarked plural. 'Chain' is not.

Blockchain is an unmarked plural

It is called a being a mass noun. They are uncountable and the singular takes the same form as the whole.

Blockchains are countable, so it does seem to be incorrect to use it as the title does.

https://medium.com/@ryanshea/blockchain-terminology-a-gramma...

(It grates on my ears to hear blockchain used the way it is here. I'm not sure when it started, but certainly doesn't sound like it should.)

Re: How Blockchain Works

#55

Earlier quoted context omitted.

Well.. It will change some aspects of our world. Particularly financial assets at first, but increasingly it will play a role in any peer to peer exchange requiring trust. Simple past examples are systems like OpenPGP that bind public keys to owners. Programmable blockchains allow generalized applications requiring decentralized trust. A good example of a use of blockchain outside of financial assets is in trust mana…

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.

Re: How Blockchain Works

#56
post #38

Earlier quoted context omitted.

Say you initiate a contract to sell a yacht for 1 million $. You and your buyer go to a notary where all 3 of you sign the contract and all the proper procedures. You give the buyer the yacht and he says he will transfer you the money tomorrow. Meanwhile the buyer and the notary strike a shady deal to screw you over and make new contracts that say you sold it for 1k$. It's 2 against 1 and you will lose a costly court…

But code isn't law. You would have to rewrite parts of the legal system to support blockchain tokens as representing actual ownership, and there's strong reasons why you would never want to, such as loss of private keys, forgetting of passwords, or security vulnerabilities, or user error leading to complete asset loss. Otherwise you have a synchronization problem between the upcoming blockchain token system and the e…

"and has a history of working just fine for lower cost." Citation needed.

Also we are just talking opinions here, a lot of things seem impossible until they are actually here and in our everyday lives.

Re: How Blockchain Works

#57
post #50

Earlier quoted context omitted.

I agree for this particular case, which is why I think a DAG with local consensus (something like IOTA) is more applicable for this application.

I think DAGs are possibly even more useless.

And you're of course free to have your own opinion. I'm not as quick to dismiss them simply because I acknowledge that new technologies have historically been ridiculed by experts at least initially. But healthy skepticism is always warranted.

Re: How Blockchain Works

#58
Question: the video explains that you can't just change a bit in the middle of the blockchain without having to fix all the subsequent blocks, making tampering labor intensive, but not impossible. Is it supposed to be VERY labor intensive, depending on the length of the chain?

Then ultimately a chain that is consistent might have been manipulated, but you can check it against other copies. At this point you could be just comparing plain text ledgers (but blockchain comparison could be easier by just comparing hashes.)

Re: How Blockchain Works

#59
post #58

Question: the video explains that you can't just change a bit in the middle of the blockchain without having to fix all the subsequent blocks, making tampering labor intensive, but not impossible. Is it supposed to be VERY labor intensive, depending on the length of the chain? Then ultimately a chain that is consistent might have been manipulated, but you can check it against other copies. At this point you could be…

The reason it's VERY labor intensive is because in a PoW blockchain, each block also includes a value that combined with the previous blocks hash hashes to a number less than the difficulty (the value labelled nonce in this demo).

The difficulty can be adjusted to ensure that finding such a number is very hard. Obviously in the demo, it was not so very difficult - your machine was able to work out a value for the nonce very quickly by itself, but in the real network, the difficult is set so that this is hard. So hard that the whole network of miners working together will only find one, on average every x minutes (configurable depending on how you update the difficulty). This means that creating another block is difficult.

The whole network has the rule that longer chains of blocks are preferred over shorter ones, so as more blocks are added to a chain, the amount of computation required to overtake the main chain and have your modified chain accepted as the truth becomes very large. To rewrite history, you don't just need to modify the data and recalculate the hash for each subsequent block, you need to find a nonce that works for each of the subsequent blocks, and you need to be doing this faster than the main chain is adding new blocks, or your chain will never be as long as the main chain, and it will never be considered the 'truth'.

That's why people talk about 51% attacks - the idea is that you need to have a majority of the hash power of the network working on your dodgy chain if you want it to overtake the main chain. Now there are things you can do with less than 51% of the network hash power, but for the naive approach, you're going to need a phenomenal amount of computing power to stand a chance of having people accept your version of history. For alt-coin chains with very few participants, there have been real attacks along these lines. It's hard to imagine attacks like this succeeding against any of the main blockchains though.

And yes, comparing two blockchains for equality is very easy - the hash of a block includes the hash of the previous block, as you can see in the demo, so the hash represents the entire history. If two blockchains have a different hash for the top block, they have different histories.

Re: How Blockchain Works

#60
post #32

Earlier quoted context omitted.

You are trying to solve a problem with a blockchain that does not exist. Also, exactly how does your blockchain even know "this yacht now belongs to this person"?

How is this not a problem if the court system is filled to the brim with situation that could have been solved with smart contracts in place. As for the yacht it's easy, the ownership is transfered from your address to the buyers address on the government's blockchain. :)

hey everyone lets record every transaction from everyone on a big government database so we can solve trade disputes if someone steals my yacht and crashes it.
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