Discussion:
[whispersystems] opt-in for contact discovery
m***@oclab.net
2016-09-27 19:55:39 UTC
Permalink
Hej,

I wonder why there is no "opt-in" for the signal contact discovery
process. Let's assume I don't want everyone having my number to know I
use signal. The only way I currently see, is using some kept-secret
number with signal, but that's pretty inconvenient. I wold love to see
some "let my contacts know I use signal" switch that can be disabled
during registration or at least an opt-out switch in the privacy settings.

@whispersystems: Do you see any value in this? Assuming (!) the need of
changes in client and server, I think further thoughts about
implementation wouldn't make any sense without your support. :-)

regards,

Mo
Emiliano Heyns
2016-09-27 20:19:58 UTC
Permalink
I'd love to see this. Or specifically a whitelist "share with this contact
group". But I've seen multiple mentions that matching all contacts is seen
as a highly desirable way to grow the signal network.

Another angle is kids-safe comms. I have an 8 year old, and I'm ok with her
chatting with her friends, but I'd dearly love to see a whitelist-only
client to curb just anyone contacting her.
Post by m***@oclab.net
Hej,
I wonder why there is no "opt-in" for the signal contact discovery
process. Let's assume I don't want everyone having my number to know I
use signal. The only way I currently see, is using some kept-secret
number with signal, but that's pretty inconvenient. I wold love to see
some "let my contacts know I use signal" switch that can be disabled
during registration or at least an opt-out switch in the privacy settings.
@whispersystems: Do you see any value in this? Assuming (!) the need of
changes in client and server, I think further thoughts about
implementation wouldn't make any sense without your support. :-)
regards,
Mo
Emiliano Heyns
2016-09-28 08:29:04 UTC
Permalink
I forgot to make sure my responses also went to the mailing list, sorry;
this is the aforementioned elaboration to Stephen.
Hello Stephen,
I am having a hard time seeing the value in this.
OWS does't have identity data paired with your phone number, and anyone
with your phone number can already contact you via SMS. So making the
1. Anyone can see that this phone number is in service and uses Signal,
but not who owns the number.
2. People who know your phone number can see that you use Signal.
Could you elaborate more on why you care about the release of that
information?
Thanks for your elaboration, I didn't make what I'm trying to achieve
clear at all. What's below is just my motivation, not necessarily a request
to add such features verbatim -- although I would of course be happy should
something like these appear.
You are right that, in principle, anyone who is my number can attempt to
text me, and you are correct I shouldn't have as a primary goal to prevent
that; contacts filtering really only a derivative goal. So here are my
1. For me personally, way too many people (some 3.5k) have my
work/personal number through the corporate directory, which is synced to
work phones. I'm happy for my colleagues to contact me during business
hours. But the off-hours messages were really eating into my family life,
so I've arranged it so that office mail/text messages/calls are blocked
outside office hours. For mail, this is done easily enough by just
disabling account sync for the exchange account; for SMS/calls, I have a
filtering app that suppresses notifications for contacts grouped into a
particular contact group (all my office contacts). This is done with a
combination of Tasker and RCB, which I acknowledge makes me a
non-mainstream android user.
2. For my daughter, the same filtering app (RCB) not only suppresses
the notifications but silently deletes text messages from numbers that
don't appear in a contact group I've set up as a whitelist.
I know 2) is easily subverted in a technical sense, but it's sufficient
for my purposes.
So I'm not really looking for contacts filtering perse, I just figured if
I could do contacts filtering, I would be sort of halfway to where I really
want to be. If I can't filter what gets through, not having people know I
use signal sort of achieves the same. I've tried to set up XPrivacy to
achieve the same outcome, but its contact whitelisting feature is rather
hit-and-miss. I was actually considering baking these features into a fork
of Signal, which I intended to put on the Play Store for free; a few
parents at my daughters' school have shown interest, and I don't want them
ticking "unknown sources". But the discussion on the LibreSignal tracker
<https://github.com/LibreSignal/LibreSignal/issues/37#issuecomment-217211165> makes
me think this would be unwelcome, so I'm looking at alternative ways.
I also experimented with Wire, which allows setup with an email address
instead of a phone number, but I'm unsure whether Wire stacks up to Signal,
security-wise, and if I'm going that route I might just as well use
Telegram, which does allow 3rd party clients to connect to its servers, and
which is a lot more popular than Wire. But I'd trust Moxie's work over any
of those alternatives, so that still has my preference.

Moxie Marlinspike
2016-09-27 22:59:41 UTC
Permalink
The mechanism you're referring to does not happen on the server or your
device, it's a locally generated notification on the device of someone
who has you in their contacts. The server isn't maintaining a social
graph or sending notifications to anyone when you install Signal.
Similarly, someone can always determine that you're a Signal user just
by sending you a Signal message.

A fundamental objective of Signal is to make it easy for people to
communicate privately with each-other. It sounds like you want to make
it difficult for people to contact you over Signal, beyond just blocking
people, which is going to be a tough sell.

- moxie
Post by m***@oclab.net
Hej,
I wonder why there is no "opt-in" for the signal contact discovery
process. Let's assume I don't want everyone having my number to know I
use signal. The only way I currently see, is using some kept-secret
number with signal, but that's pretty inconvenient. I wold love to see
some "let my contacts know I use signal" switch that can be disabled
during registration or at least an opt-out switch in the privacy settings.
@whispersystems: Do you see any value in this? Assuming (!) the need of
changes in client and server, I think further thoughts about
implementation wouldn't make any sense without your support. :-)
regards,
Mo
--
http://www.thoughtcrime.org
Emiliano Heyns
2016-09-28 07:58:13 UTC
Permalink
Post by Moxie Marlinspike
The mechanism you're referring to does not happen on the server or your
device, it's a locally generated notification on the device of someone
who has you in their contacts. The server isn't maintaining a social
graph or sending notifications to anyone when you install Signal.
Similarly, someone can always determine that you're a Signal user just
by sending you a Signal message.
A fundamental objective of Signal is to make it easy for people to
communicate privately with each-other. It sounds like you want to make
it difficult for people to contact you over Signal, beyond just blocking
people, which is going to be a tough sell.
Hello Moxie,

You're right that I provided a confused case. Does my elaboration in
response to Stephen clear this up?

I suppose you're right that I want to make it difficult for people to
contact me (over Signal or otherwise) under specific circumstances. It's
not so much that I single out Signal. I'd love it for people to contact me
over Signal rather than over SMS, and I'd love there to be an extra reason
I could give (but this reason could very well be wholly peculiar to me) to
have people use Signal rather than Whatsapp. In the 2nd case I described to
Stephen, there's some discussion going on at my daughters' school how we
can safely have these young children chat outside school hours (which is
something many of these young children want, specifically the girls for
some reason), but we don't want to put them on whatsapp. In the case of my
daughter, I took out the sim after activating Signal on her phone, so
people who have her "signal number" won't be able to call her except over
signal itself.

I do fully realize this is a specialized case.

Thanks,
Emile
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