[messaging] Encrypted Pulic Contact Discovery

steve at actor.im steve at actor.im
Wed Aug 19 10:47:00 PDT 2015

Hi Moxie,

I don't think that anything decentralized will scale on mobile at all. That's why we (https://actor.im) are focused on running servers that assist mobile environments and do all dirty work. Servers allow me to do various nice things like keeping my history, do processing of messages (like creating tasks from chat?). I haven't found a good solution for storing messages history (even in this mailing list) and for now best thing is to have your servers.

My article is mostly about server-to-server communications and not mobile-only.


19.08.2015, 20:34, "Moxie Marlinspike" <moxie at thoughtcrime.org>:
> On 08/19/2015 08:26 AM, steve at actor.im wrote:
>>  Hello everyone!
>>  Just finished small article about one idea of secure contact
>>  discovery:
>>  https://medium.com/@ex3ndr/encrypted-public-contact-discovery-95cfa0a0f6c7
> Publishing the entire directory is one approach to PIR, but it won't
> scale on mobile with an even moderately sized user base. We started out
> using a bloom filter for RedPhone, which is more space efficient than a
> directory of hashes and encrypted tokens, and have already hit the limit.
> For what it's worth, I wrote a small summary of techniques and why none
> of them work at scale here:
> https://whispersystems.org/blog/contact-discovery/
> Using PBKDF2 also won't stop someone from inverting your entire
> directory, since the preimage space is so small. If that's an important
> feature, encrypted bloom filters are probably a better option, since
> that at least allows you to rate limit server-side and is thus no worse
> than traditional contact intersection. But, again, it won't scale.
> - moxie
> --
> http://www.thoughtcrime.org
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