[dmitriid]

> Obviously a blockchain cannot magically make people do things they don't otherwise want to do.

So, what's the point, really, especially if talk about "Distributed trust" if blockchain provides nothing to ensure that trust?

> But what a blockchain can do is model parts as tokens that can only exist once on the chain, associate data like provenance documents with each token, then model sales as transfers of the token... a way that you don't have to trust any single entity

So, the details and provenance magically appear on the blockchain. Who verifies them? Who makes sure they are complete? Let me guess, some centralised/external entity?

So, there's some part associated with a token. What's to stop me from associating the same part with a different token? Or with 100 tokens? I'm guessing there is some centralised agency that verifies that a part is associated with a token through the part's serial number and that: a) no other token is associated with the same number and b) the seller associates serial numbers, and not some random numbers with the token?

I'm not even going into such things as "seller A sold part B to buyer C, received the money and never sent the part", let's start with documents, parts, tokens and associations.

[damnyou]

Yes, you need a trusted path to go from physical reality to the token on the blockchain. But blockchains let you shrink that path down to a small number of operations that can be closely scrutinized. (This is how blockchains are similar to cryptography, where the goal is to secure a large amount of data by keeping a small amount of data secret.)

As far as how to build that trust goes, what you're talking about is similar to the certificate signing problem. There are at least two ways to do this — a hierarchy trusted by everyone (akin to PKI) and a decentralized web of trust. Blockchains let you do either or both of those things since entities can sign off on the provenance on the blockchain. You can also have multiple entities sign off on it, similar to GPG keys.

[dmitriid]

> Yes, you need a trusted path to go from physical reality to the token on the blockchain.

You mean a centralised entity that is able to verify all claims input on the blockchain, cross-reference these inputs, and then enforce the execution of the contract.

Why would you need blockchain then if you trust such an entity with so much more than just with part tracking?

> Blockchains let you do either or both of those things since entities can sign off on the provenance on the blockchain.

wat

> You can also have multiple entities sign off on it, similar to GPG keys.

So, blockchain "solves" exactly one thing: inventory tracking. And does it in an overly complicated and highly inefficient way. Everything else is entrusted to external entities.

To quote an amazing article [1]

--- start quote ---

People treat blockchain as a “futuristic integrity wand”—wave a blockchain at the problem, and suddenly your data will be valid. For almost anything people want to be valid, blockchain has been proposed as a solution. It’s true that tampering with data stored on a blockchain is hard, but it’s false that blockchain is a good way to create data that has integrity.

Blockchain systems do not magically make the data in them accurate or the people entering the data trustworthy, they merely enable you to audit whether it has been tampered with.

How then, is trust created?

... if you look at any blockchain solution, inevitably you’ll find an awkward workaround to re-create trusted parties in a trustless world.

--- end quote ---

[1] https://medium.com/@kaistinchcombe/decentralized-and-trustle...

[damnyou]

> You mean a centralised entity that is able to verify all claims input on the blockchain, cross-reference these inputs, and then enforce the execution of the contract.

...

> wat

My belief that you're arguing in good faith is slowly but steadily dropping. I just went over how you could have a network of such entities instead of a single centralized one. This is a policy question that's orthogonal to whether you use a blockchain for this.

> Why would you need blockchain then if you trust such an entity with so much more than just with part tracking?

Trust is not a simple yes or no thing. Blockchains make trust relationships legible and verifiable. You can go back in time and get cryptographic proofs of historical trust relationships.

I'm normally a blockchain skeptic but provenance tracking is a very good use of them.

[dmitriid]

> My belief that you're arguing in good faith is slowly but steadily dropping.

Nope. I'm just trying not to spell out every little thing that a blockchain solution doesn't provide because they should be obvious. But apparently they aren't. See below.

> Blockchains make trust relationships legible and verifiable.

They don't. They literally don't. The only thing that a blockchain solution provides is that once entered the data can't be tampered with. Which is the smallest part "a marketplace for plane parts" does.

It's easy to see if you split things into "what is done on the blockchain" and "what is done outside the blockchain via centralised entities".

On the blockchain:

- verify that once the data is entered it's not tampered with.

Outside the blockchain:

- verify that details and provenance documents are complete

- verify that the same part isn't listed multiple times

- seller ratings to aid prospective buyers

- buyer ratings (rarely public, but can be implemented to aid dispute resolution)

- verify that a seller doesn't inflate the ratings via fake accounts "buying" a lot of merchandise

- dispute resolution and arbitration when the merchandise isn't delivered, or delivered not as described, or when the buyer withdraws payment, or...

- other fraudulent activity (non-existing sellers/buyers/parts/fakes/replicas/...)

I'm definitely missing more. All of the above require trust, and non of the above are aided in any way, shape or form by a blockchain solution. As evidenced by cars' VINs, provenance tracking is a somewhat solved problem outside blockchain, and there's little to nothing that a blockchain solution can bring to the space.

[Reelin]

From your own quote:

> they merely enable you to audit whether it has been tampered with

That's literally the entire point here (if I've understood correctly). If anyone tried to falsify even the slightest detail, including Honeywell or an entity hosting the database on their behalf, you can be reasonably certain that you would notice it. The history of each serial number becomes effectively immutable once entered into such a database, which is presumably a very good thing given what these parts are used for.

I'd love if purchasing a used car came with anywhere near that level of guarantee about its history.

[dmitriid]

> If anyone tried to falsify even the slightest detail, including Honeywell or an entity hosting the database on their behalf, you can be reasonably certain that you would notice it.

You can only notice it once the data is entered. What's to stop me from entering false data? What's to stop me from entering multiple false entries? etc.

More here: https://news.ycombinator.com/item?id=20074643