OpenPGPEmailSummit: Encrypted Indexes

Workshop at 2nd OpenPGP Email Summit, Dec 2015 run by dkg


This are raw notes, they might not be complete and/or too cryptic.

about the attacks to on demand fetch

As long as you store emails in the server and you retrieve them on demand your provider will be able to guess the content of your encrypted emails. I'll explain it.

Imagine that you have the index in perfectly secure way, or locally stored or an ideal nifty way in the provider where you can do queries and the provider can not guess the content of the queries.

Let's first assume that you have your emails stored as they arrive, your encrypted email is stored encrypted and your decrypted email is stored decrypted. After each query you retrieve the resulted emails, so the server sees which decrypted emails are related to which encrypted ones and in the long term can infer the content of the encrypted ones as well.

Let's imagine then that you store all the emails encrypted. Then your provider could send to you crafted emails with the kind of content she cares about to discover, so it can notice each time you retrieve one of this crafted emails and what other emails are related to that.

You could minimize this attack by not only fetching the emails that you care about, but fetch way more. But at the end or you have your whole set of emails locally or the server will be able to infer data about the encrypted emails.

local model

OpenPGPEmailSummits-EncryptedIndex (last edited 2016-01-07 09:24:52 by josuttis)