Could someone tweak the image? Of course. But as a practical concern, probably less than 20 people have the image manipulation skill it would take to do something like this in the ~20 minute handoff period. The transporters certainly don't. This is a bullshit argument, and you know it. And these pictures are not just of the odometer, but the entire car, including the VIN. Photoshopping all of this believably would cost you more than just paying the damages on a joyride. It's a non-issue.
And I think you're misunderstanding something: the issue is not the time before the transporter get custody of the cars, but the many days that the cars are in transit cross-country. If the timestamp didn't exist at the time the transporter starts their journey, the next handoff knows something is up.
As for already trusting us, our clients do, yes, but the point of this solution is to increase the trust-level of custodianship handoff between people who are not our clients. A blockchain is a great solution for this, and a database is simply an inferior solution. And NO, they don't have to trust us to "push the right data on-chain". This logic runs in a very simple SPA and is immediately verifiable on-chain, without using our software, because the blockchain's global state is open.
If you're arguing to put everything in a spreadsheet, or have us control the database and do without timestamping, I don't know what to say to you. Blockchain works here. Our business model isn't changing because you're saying we don't need it. Build a system like this yourself and we'll talk about it then.
Carfax is a vertically integrated service with very little of the complexity we're dealing with. And of course you can make do without blockchain. People made do without electricity and power tools. But here it's a cheap, faster, easier to use, and more trusted alternative. What's wrong with that?
Done. It's an email server. The person shipping the car takes a photograph of the odometer, emails it to the recipient, and then the recipient compares the photograph of the odometer with the car odometer. Any tampering which could be performed on the photo or its timestamp could be done equally to whatever log is entered into the blockchain, and the recipient knows that the photo must have been taken before the date when they received the email.
And if you use gmail, it's free.
This way both parties could verify the transaction was completed as contracted (IE no joyrides).
I'm still in the camp this probably doesn't need blockchain, but that would at least handle the image manipulation problem.
But yes, depending on the application, photos can be manipulated. But that is stating the problem with using photos, not the timestamping app.
Basically, yes, you could, in theory, maybe, sort of, possibly, build a similar system without a public blockchain. But why? I'm sure there are people who can build houses with a few hand tools, but there's a reason we have power tools and heavy machinery — they are more efficient and fit the job better. The same goes for blockchain in this case.
If you can point out where my logic is incoherent, please do, but to me the following: "oh, just set up a distributed git repo or database with checksums and append-only permissions that you control but replicate to other servers not controlled by you so that you can't tamper with the outputs and read from that global state and verify against the other mirrors of the database or repo every time you read from global state" sounds like a stupider alternative to blockchain.
This is what blockchains were made for!!! Distributed consensus!
Also what is the point of mining or and proof of $whatever system? The thing your customers provide is a signed attestation of some fact and you provide a signed attestation of the time that fact was received. Why is there a need to "vote" in way on what is true? This is just a database or honestly a folder of signed messages.
And I say signed, but none of this really need to be cryptographic in any way since they're customers that could just authenticate to you which is as much a proof of their identity as any key.
The way the transporters know they're getting a fair deal is precisely because we are not the source of truth — a database outside of our control is (a blockchain, in this case).
We're not voting on what is true, we're relying on the blockchain as an immutable representation of state. An append-only, distributed database that we do not control.
And please don't downvote my comments out of a misunderstanding. That's juvenile.
This is a trust problem. Either people trust you, or they don't. You've attempted to increase their trust in you by creating a system that would increase somebody's trust if they had your understanding of the underlying technology. Very few people have this, and the overlap between the people with that understanding and your customers and clients is vanishingly small.
Trust really isn't binary.
> would increase somebody's trust if they had your understanding of the underlying technology.
Or if they had a handwaivey "I've heard that blockchain increases the verifiability of things" level of understanding.
In this specific example, what would they change to photo to? The case is to stop joyrides. Who would be able to take a joyride and end up with the odometer exactly as they had Photoshopped it to hours or days ago?
But yes, depending on the application, photos can be manipulated. But that is stating the problem with using photos, not the timestamping app.
I'm not discouraging you. Just to say your blockchain backed solution is a fair solution but it's not the only solution.
It would require cooperation from auto manufacturers but I'm sure you could come up with a scheme where the car itself signs and timestamps mileage data.