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I was looking into some papers regarding proof of data possession like this or thisin cloud storage where you can ask for the proof of the data stored in the cloud storage by giving some kind of challenge to the server and server will reply back with the result of the challenge by calculating the object stored in the cloud server. But as far as I know some of the public cloud storages like AWS S3 does not allow for other object operations of calculating the object using some formulas other than download, upload, or listing the file (CMIIW). Now the question is the proof of data possesion still possible to do that in the cloud storage? If so, how?

Ihsan Haikal
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Azure blob storage offers per-block MD5 (which can be requested to be dynamically calculated using an http header in the REST api request).

If you want to, you can write a client which validates the content of cloud-stored blocks by iterating over the blocks in each blob, requesting the MD5 for each range and comparing it to local data.

It's a pretty mature API at this point: here's the overview from 2011.

I'd be surprised if AWS didn't offer something similar.

Nathan
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  • i guess that could work but what i had in mind is that the cloud is able to compute based on the formula of data possession that we give and based on the result we can compare with our calculation to see if it matches or not – Ihsan Haikal May 05 '17 at 15:05
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    @IhsanHaikal you can always write an application which runs in their data centre and does whatever calculations you like on the data there... your code, your calculation/operations. ? For Azure, I would just write an Azure function (https://azure.microsoft.com/en-gb/services/functions/) which accepts an input which locates the data in question (for example, a container path), performs the necessary calculations on the storage account / blobs and returns the result. – Nathan May 08 '17 at 09:09