[ghthor]

You need that text file signed by your previous doctors, and your new doctor needs to be able to verify the public keys of your previous doctors using some type of PKI. You also need to locally manage your health records data, its storage can't be easily automated and paid for. Blockchain solves all of those problems in one nice bundle, it provides PKI, signed log of changes, and distributed automated storage. That's one hell of a feature set.

[greggman]

As far as I understand the point is supposed to be the blockchain is distributed trust. The longest chain = proof of most work = the truth. The only reason someone can't basically change the entire history of the blockchain is because no one has 51% control of the chain. The only reason no one has 51% control of the chain in bitcoin is because so many people are mining it to earn coins.

But, for medical records there is no such incentive. Therefore anyone can easily change the records or add new ones and claim everyone else who has a shorter chain has the wrong chain (which will be like no one since there is no incentive to mine).

So I'm probably just informed how blockchain is supposed to help here. Without the distributed trust there's no plus to blockchain. And without the incentive to mine that generates millions of miners there is way to have the distributed trust.

I'm happy to be wrong but I haven't see an explanation how this issue is solved for all these non virtual currency uses cases.

[ghthor]

Using bitcoin(I know less about how to store data into bitcoin transactions) you can execute a transaction and store a small piece of data that would be a reference to a larger blob of data, say an IPFS hash to an encrypted MRI image and the doctors notes. You use bitcoin to store the log of changes using reference to some type of immutable data store. It's imperfect, but can be built. The value add of the bitcoin here is it's extremely hard to create a false history and tell that as the real story.

Ethereum would be easier to understand and see what's going on because we have a reasonably readable contract language. You'd still likely need to store larger blobs of data using an external immutable data store, and those blobs wouldn't be automatically distributed and backed up. But you could pay for distributed backups in an automated way using ether. Lots of people working on this last part, which drastically reduces the potential size of the blockchain because it will only be afordable to log blob references and numerical values.