If this is some cloud provider, what are you getting from a blockchain? Just have the cloud provider do the certification. If they betray you or go out of business you've lost your hashes anyway.
If it's stored on the endpoint device, you can't prove it anymore if the device gets lost or damaged. In theory people could back them up, but we all know perfectly well that ordinary people are not going to do that unless it's automated.
So then you're back to storing them in a distributed system, i.e. making them a necessary part of the blockchain. And then it gets too big.
