[Cryptography] Signal chat fallout.

[iang]

On 29/03/2025 02:35, Henry Baker wrote:
> ...has an app -- at least for iPhones (I couldn't find it in the 
> Android Play Store) -- that claims to eliminate the embarrassing 
> problem with Signal group chats  -- what Kent is referring to above as 
> problems #2 and #3.


I had a read of their FAQ.

The design of that app is good, as far as it goes. Its meta is to force 
everyone into a group, and have the group strongly govern the new 
members. in the simple sense, it would have blocked JG from joining the 
group.

But look a little deeper and it won't meet all the requirements. 
Firstly, the group is high cost construct (as constructed by that app) 
and is unsuited to constructing groups on the fly - which is what 
exactly happened in the SignalGate case, and is a feature that p2p apps 
excel at. Secondly, the weakness is in adding new members. This also can 
be spoofed, and will be by Lazarus, simply by knocking a member out of 
the group when he's remote, and then spoofing the photo mechanism with 
live AI. Thirdly, because it has a corporate/business model, it's 
vulnerable for anyone who counts USG amongst their adversaries.

Now, for the most part, the design is good - and it is the same design 
as I have for groups. The difficulties mentioned above are more the 
product of the environment - what are the groups and how do they 
perform/not perform. Tech is only limited in its ability to mitigate 
those weaknesses.

iang