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Comment by garmaine | Hacker News Reader

What are semaphores useful for? That’s the question you are asking really. Bitcoin is a global, non-trusted semaphore/mutex lock system.

A “smart contract” is basically an ordinary payment contract where execution steps are gated by separate semaphore controlled by sunsets of the participant set.

What can you do with that? It’s hard to answer without being so general as to be useless, or without getting too specific such that we lose the big picture.

“Block chain” is about replacing courts and arbitration with a computer network, and replacing contract lawyers with programmers. What makes this possible is the fair, untrusted, equal access semaphore a bitcoin spend provides.

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literally every time someone asks this really straightforward question the answer is vague tech waffle.

seriously, please: tell me one genuine use case for block chains that conventional database stack can't do?

They can guarantee that some data that indicates it was recorded yesterday was in fact recorded yesterday and not changed at any point since yesterday.

There's literally nothing a blockchain can do that a trusted central database couldn't do. So you only need a blockchain if you can't trust a central database. As a result, the answer to the question you've posed is always going to be a political one, not a technical one. ("It lets banks that don't trust each other keep a shared database of transactions." "It lets citizens who don't trust their various governments exchange currency." "It lets shipping companies that don't trust each other digitize their manifests." "It lets scientists prove their papers were published on a certain date.")

Cool, yes, one use case: you can stick document hashes in to the block chain to prove document state at some point in time. This no doubt has legal uses, and perhaps scientests too although I think less so.

Re your shipping manifest example - can you expand on this - how does this work?

Basically, when I load up your ship, I document all the stuff I am loading on to the ship in a Bill of Lading. You agree that all of that stuff is present and you're now responsible for it. At the other end of the shipping route you present the Bill of Lading and show that all the goods are present and intact.

If this document is digital, then I might get screwed if you lose stuff or stuff gets damaged and you remove it from the Bill of Lading and say you never saw the goods. Or you might get screwed if I add new stuff to the Bill of Lading after you load the goods and claim you didn't deliver it. So one way to solve this is to put the document and both of our signatures in a blockchain, and now we all agree that this is what we saw on that date.

cool thanks

Once the manifest has been added to the blockchain, it can no longer be altered or removed. This means that the receiver can publicly acknowledge having received the goods it paid for, and won't be able to retract that acknowledgement.

The main point is that, unlike a situation where you would be using a centralized database, there is no need to have a central trusted party to operate the database - the source of trust is distributed among the mining power of all nodes in the network.

thanks

It appears to be particularly useful for:

- Buying contraband

- Ransom payments

- Pump and dump schemes

- Money laundering

Remains to be seen how it will impact the everyday lives of regular people.

Regular people buy contraband all the time though.

They don't require trusting the database operator. (And why does that matter? With trust comes costs.)

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