File level retrieval

[xmcai2016]

File retrieval
If the client has provided a list of CIDs for files included in the dataset, we have the opportunity to retrieve the whole file
Retrieve the first 4k bytes of the file, check the file type using libmagic. Overtime, this will give us an overall picture of what types of files is this dataset composed of
With less sampling rate, retrieve the whole file and store it in an online storage (i.e. web3.storage). The file can be downloaded by notary to check the content