On Ghost Users and Messaging Backdoors

#1

Post by kandarpck » Tue, Dec 18, 2018, 12:10 AM UTC

On Ghost Users and Messaging Backdoors
blog.cryptographyengineering.com

Re: On Ghost Users and Messaging Backdoors

#2

Post by merlincorey » Tue, Dec 18, 2018, 1:12 AM UTC

Apparently some researchers from the GCHQ in the UK are proposing that "secure" messaging systems like iMessage and WhatsApp which manage group chats centrally in a manner that bypasses the end to end encryption should:

- Add "ghost" users/devices to existing chats

- Suppress notifications of these additions to users

This would perpetuate a currently known bug in secure communication protocols, effectively turning it into "feature" for law enforcement.

Fortunately, systems like Signal and Briar have already moved past this flaw.

Re: On Ghost Users and Messaging Backdoors

#3

Post by RcouF1uZ4gsC » Tue, Dec 18, 2018, 1:32 AM UTC

With the spread of misinformation and rage using messaging apps that have literally resulted in people getting killed by mobs (see for example https://www.nytimes.com/interactive/2018/07/18/technology/wh...) maybe we should re-evaluate our belief that making it impossible for governments to see what is spreading through messaging apps is an unmitigated good?

Re: On Ghost Users and Messaging Backdoors

#4

Post by Spooky23 » Tue, Dec 18, 2018, 1:46 AM UTC

RcouF1uZ4gsC wrote: post #3

With the spread of misinformation and rage using messaging apps that have literally resulted in people getting killed by mobs (see for example https://www.nytimes.com/interactive/2018/07/18/technology/wh... ) maybe we should re-evaluate our belief that making it impossible for governments to see what is spreading through messaging apps is an unmitigated good?

I agree. There’s often an extreme point of view here with respect to this.

Re: On Ghost Users and Messaging Backdoors

#5

Post by jeklj » Tue, Dec 18, 2018, 1:55 AM UTC

RcouF1uZ4gsC wrote: post #3

With the spread of misinformation and rage using messaging apps that have literally resulted in people getting killed by mobs (see for example https://www.nytimes.com/interactive/2018/07/18/technology/wh... ) maybe we should re-evaluate our belief that making it impossible for governments to see what is spreading through messaging apps is an unmitigated good?

Maybe we should consider that goods can still be worthwhile despite their mitigations.

Re: On Ghost Users and Messaging Backdoors

#6

Post by EGreg » Tue, Dec 18, 2018, 1:57 AM UTC

merlincorey wrote: post #2

Apparently some researchers from the GCHQ in the UK are proposing that "secure" messaging systems like iMessage and WhatsApp which manage group chats centrally in a manner that bypasses the end to end encryption should: - Add "ghost" users/devices to existing chats - Suppress notifications of these additions to users This would perpetuate a currently known bug in secure communication protocols, effectively turning it…

What does that mean, “manage centrally in a manner”... and how does Signal not manage it centrally?

Re: On Ghost Users and Messaging Backdoors

#7

Post by vonseel » Tue, Dec 18, 2018, 2:03 AM UTC

EGreg wrote: post #6

merlincorey wrote: post #2

Apparently some researchers from the GCHQ in the UK are proposing that "secure" messaging systems like iMessage and WhatsApp which manage group chats centrally in a manner that bypasses the end to end encryption should: - Add "ghost" users/devices to existing chats - Suppress notifications of these additions to users This would perpetuate a currently known bug in secure communication protocols, effectively turning it…

What does that mean, “manage centrally in a manner”... and how does Signal not manage it centrally?

Signal groups are managed by the client devices. The details are quite complicated, but some are documented here: https://signal.org/blog/private-groups/

Perhaps another user with stronger familiarity on the subject can expand on this (ELI5 would be great!).

Re: On Ghost Users and Messaging Backdoors

#8

Post by tjoff » Tue, Dec 18, 2018, 2:05 AM UTC

Instead of creating a ghost user account and attempt to join a chat, why not just copy they key of one of the participants?

Re: On Ghost Users and Messaging Backdoors

#9

Post by RcouF1uZ4gsC » Tue, Dec 18, 2018, 2:05 AM UTC

jeklj wrote: post #5

RcouF1uZ4gsC wrote: post #3

With the spread of misinformation and rage using messaging apps that have literally resulted in people getting killed by mobs (see for example https://www.nytimes.com/interactive/2018/07/18/technology/wh... ) maybe we should re-evaluate our belief that making it impossible for governments to see what is spreading through messaging apps is an unmitigated good?

Maybe we should consider that goods can still be worthwhile despite their mitigations.

I agree, but when you do that, you need to actually make an accounting of the costs/benefits. If you look among programmers and security specialists on say HN there is not even a debate or discussion about this, but rather an absolutist position that this is good and that the only reason to think this is bad is if you are a totalitarian government wanting to oppress your people.

Re: On Ghost Users and Messaging Backdoors

#10

Post by vonseel » Tue, Dec 18, 2018, 2:07 AM UTC

RcouF1uZ4gsC wrote: post #3

With the spread of misinformation and rage using messaging apps that have literally resulted in people getting killed by mobs (see for example https://www.nytimes.com/interactive/2018/07/18/technology/wh... ) maybe we should re-evaluate our belief that making it impossible for governments to see what is spreading through messaging apps is an unmitigated good?

What makes you think these "mobs" used WhatsApp for its security reasons? I'd expect it's far more likely they use WhatsApp because it's the most popular messenger in that part of the world.