Re: [tor-talk] hierarchy anonymity

[Sean Lynch <seanl@xxxxxxxxxxxx>]

A naive, probably inefficient approach would be to have everyone tweet
fixed-length encrypted messages encrypted with each of the others' private
keys, including the teacher's, at the same time every day. Everyone would
also download everyone else's tweets and attempt to decrypt all of them.
All but the teacher's message would be random garbage with a broken
signature or message digest. Provided you always sign, then encrypt, and do
not leak any information about the recipient's public key in the
ciphertext, it should be impossible to see who's sending valid messages.
I'm thinking a cipher like curve25519-xsalsa20-poly1305 so that the
ciphertext fits in a tweet, at least if you strip the
https://en.wikipedia.org/ off the front.

On Thu, Feb 4, 2016, 11:17 Jonathan Wilkes <jancsika@xxxxxxxxx> wrote:

> Hi Tor,Suppose there are twitter users @Alice000...@Alice999 who all know
> each other's public key.  One of them is
> a teacher of an online security class.  The rest are students.
> The class consists of the teacher sending the students a link to a
> Wikipedia page each day, for an entire year.  Each day every member of the
> class (including the teacher) must visit that Wikipedia page in the clear.
> The teacher may only communicate with the class using Twitter (though the
> tweets may be encrypted using students' public keys).
> Is there an extant messaging protocol that would hide the student/teacher
> hierarchy if all communication metadata is
> public?
> -Jonathan
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