There’s a lot of buzz in the digital health world about “blockchains” – unalterable records of history. Those looking to make money are looking adoringly at the health IT budgets.

No health app, data, or service, involving blockchains, should be considered credible without publishing specific worked examples of what data is written to the blockchain.

That must be the key test to allow a discussion of privacy. Without that, no credible assessment can be conducted. Is there a worked example of what will be recorded, for each of 7 entities involved, for an average of 5 transactions each?

If you don’t know what information is recorded, it’s impossible to analyse whether the promise is a sweet dream or a beautiful nightmare.  For different scenarios, it will be different – Beauty is in the eye of the beholder

In the 1990s, Iceland decided that it would give “a single company monopoly control of the country’s health records”. The system was cancelled when it was demonstrated that individuals could be identified.

As so often in the tech world, there is an incentive for a shiny press release which ignores past failures. Those failures being forgotten until they are repeated. With blockchains, that may be a much less private event.