[hzsvabya] Searching and retrieving encrypted data

Consider encrypted data stored on a cloud storage service that charges per amount of data stored and per the amount of data transfered in and out of the cloud.

Naively searching the encrypted data by downloading it to a secure machine where it is decrypted and searched would incur large data transfer costs.  On average, half the data would need to be downloaded.

More clever would also store encrypted indices to aid search, incurring additional storage cost while decreasing data transfer costs.

Optimize the system, the construction of the indices, for given data storage and bandwidth prices.

With indices, even encrypted, access patterns can leak information to an adversary.