[Cryptography] multi-key encryption of "meta" data

Christian Huitema huitema at huitema.net
Sun Jul 20 20:30:22 EDT 2014


> a.  Come up with a protocol so that the mail server doesn't know who got
what.  
> (This looks hard to me--it's related to searching on encrypted data, but
looks 
> harder than that to me.)  

I have seen designs trying to achieve that with basically a drop box. Drop
an encrypted file at some random location, then arrange for the intended
recipient to get the key and the location. Of course this is merely a way to
achieve one degree of indirection, there is still a need to pass the key and
location.

> b.  Replace the single mail server with some kind of network of nodes
controlled by different 
> entities.  What we know how to do right now is build a remailer network
with some kind of 
> longish delay, along with some kind of service that lets users drop
information and chaff 
> into/out of the system. 

There is a tradeoff between traffic analysis and the number of nodes. A
single node creates a single point of observation. Too many nodes allow for
easy correlation of who connects to what...

-- Christian Huitema




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