• 8 Posts
  • 440 Comments
Joined 3 years ago
cake
Cake day: July 2nd, 2023

help-circle




















  • Yes, subpoena was poorly worded. NSL is more likely. But still it is a time-forward threat, which means there is value while the server is or was accepting sealed sender.

    And I wasn’t suggesting timing attack is required to defeat sealed sender. I was, on the contrary, pointing out that was a threat even with sealed sender. Though that is non-trivial, especially with CGNAT.

    So in summary. You’re right. Sealed sender is not a great solution. But it is a mitigation for the period where those messages are being accepted. A better solution is probably out there. I hope somebody implements it. In the meantime, for somebody who needs that level of metadata privacy, Signal isn’t the solution; maybe cwtch or briar.


  • Sure. If a state serves a subpoena to gather logs for metadata analysis, sealed sender will prevent associating senders to receivers, making this task very difficult.

    On the other hand, what it doesn’t address is if the host itself is compromised where sealed sender can be disabled allowing such analysis (not posthoc though). This is also probably sensitive to strong actors with sufficient resources via a timing attack.

    But still, as long as the server is accepting sealed sender messages the mitigation is useful.


  • Don’t mistake me for saying you’re wrong. I agree with you, mostly. But sealed sender isn’t theater, in my view. It is a best effort attempt to mitigate one potential threat. I think everybody would like that solved but actually solving it isn’t easy as I understand it. Maybe not intractable, but if you have a solution, you can implement it. That is one of the things I like about free software.

    In any case, I’m only saying Signal is good for a subset of privacy concerns. Certainly not that it is the best solution in all cases.