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I doubt that you could ever fully protect against it. I think, and I'm not an expert here, that the VeChain method relies on automated smart sensors which record (and possibly log, I don't know) data onto the chain, combined with a set of trusted individuals who know how and where to read data in. They follow products from start to end i.e. from harvest/manufacture to the final point of sale, logging all major data along the way. I hope that sort of answers your question; sorry I'm not specialised/knowledgeable enough to elaborate further.

Sure, no problem, not an expert on the technology but, based on what you're saying, it sounds a lot like this application doesn't really need a blockchain:

automated smart sensors

oracle problem: again how do you make sure that the data that comes in is not junk.

trusted individuals:

this one speaks for itself, if at the end of the day you're going to rely on trust then a blockchain doesn't seem to be necessary, but as I said I am not familiar with the finest points about this technology.