5 ms·

Improving Signal's Sealed Sender (2021)

72 points by ementally 4y ago

ShrimpHawk 4y ago
from 2021
phneutral26 4y ago
Consider adding 2021 to the post title, for clarity. Anyhow, interesting article. Thanks for sharing.
palata 4y ago
Interesting analysis! Showing (once again) that anonymity is difficult to achieve.
tandr 4y ago
Did Signal fix the protocol, or at least responded with something?
- ementally 4y ago
  Nope, according to https://community.signalusers.org/t/sealed-sender-still-broken-or-already-fixed/49978 https://community.signalusers.org/t/sealed-sender-still-brok...
  - wkat4242 4y ago
    That's pretty bad 2 years later..
    - tptacek 4y ago
      I guess? This is an anonymity feature no other mainstream messenger has in the first place. The idea behind sealed sender is that clients can send messages through Signal's service without authenticating directly to the server. It's not, like, part of the core E2E mechanic of Signal; I'm not even sure it was ever out of beta.
    - upofadown 4y ago
      The suggested fix was pretty complicated and had some drawbacks (see section VII-B). Signal probably did not agree that it was worth it. It's a hard problem and it just might be the case that no one has of yet come up with a workable solution.
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godelski 4y ago
FYI I don't think Signal cares much about anonymity (sadly). I've seen several discussions on their forums where admins have even been hostile to people asking for it. I love Signal, but its community is toxic and I really wish the devs would move a bit faster. I know it is a tall order, but that's what Moxie argued in his "The Ecosystem is Moving" talk (we can't have decentralized because you have to move fast and adapt). There's a lot of low hanging fruit that Signal just seems to ignore.
- tptacek 4y ago
  However much they care or don't care about it, the salience of this NDSS paper is that Signal has a relatively complex anonymity feature that no other mainstream messenger has (the ability to cryptographically authenticate a message that can be delivered via the service without the client authenticating to the server), and it's susceptible to some straightforward network timing analyses. There may be any number of other reasons to believe that Signal doesn't care enough about anonymity, but with respect to this paper, the most you can say is that they don't get full credit for an extra credit anonymity project they did.
  - godelski 4y ago
    Oh, I use Signal and still push my friends and family to use it. I'm not arguing against it. You're right that it is still a great app that does things others don't. As to anonymity, I'm more frustrated with the community being hostile against other community members asking and pushing for it. I do understand that the community isn't the signal team, but it is their official community so it does set the tone. Especially since they specifically note that that's the only community they pay attention to. (e.g. GitHub bug reports should be on community) As for non-anonymity stuff, there are quite a lot of extremely low hanging fruit that is weirdly not available but highly asked for. Like having to go to https://signalstickers.com/ https://signalstickers.com/ to get stickers? This should clearly be accessible through the app (or they should be hosting their own). Delayed messages are thankfully here but took forever. For some reason forwarding messages on phone vs computer has different behavior (I can edit from the computer; the preferred method). Still can't find messages associated with media. Can't star/favorite messages. These are very important features that each could be done in less than a weekend so it just seems odd. I do want to see Signal be more used and I want to see it grow. I love it and advocate for it, but that also doesn't mean I'm not going to be critical of it when it is having issues.
autoexec 4y ago
My impression is that since around 2020 Signal devs have been trying as quietly as possible to tell people that the service can no longer be trusted and everyone should switch to something else. First they started keeping sensitive user data in the cloud which upset and alienated a bunch of users, they've also refused to update their privacy policy to reflect that fact, then they added the weird crypto thing which upset more users, and killing off the ability to handle SMS/MMS as well as secure communications, one of their best features, seems like yet another attempt drive away users. Maybe going years without fixing important features with known vulnerabilities is just another hint being left to ward off anyone who really needs their communications secure. I loved signal and recommended it to many people over the years, but I ditched it after they started collecting and insecurely storing user data in the cloud, and I'm still disappointed in what it has turned into. The folks behind Signal had a great project once and I hope someone outside of the US steps up to give us a real replacement one of these days.
- ChuckNorris89 4y ago
  Me and my family ditched Signal this week after 2 years of struggle. The calls refusing to ring on our 3 different brands of Android phones, only to be greated by a missed call notification later, despite disabling all the battery optimization features on each phone meant the app was unusable for us. It always rings on the PC app, but on our phones it's always hit or miss. Only once you open the app when someone is calling you, does it finally decide to ring. Googling around it seems many are impacted by this bug which has been around since forever, but no fix has been implemented and since the dev team seems mostly iOS focused, I doubt it will ever be. The lack of supporting linking to Android tablets is another blow for us when iPad support has been available since forever. Shame. I respect Signal and its devs for doing what they did, but we need more than a barebones messaging app with focus on stickers and stories instead of fixing jarring bugs and missing Android features, so it looks like it's back to WhatsApp for us. It may be part of Zuck's empire but it has never ever let us down in any situation.
  - raybb 4y ago
    Bummer. Have you given Element a shot recently? It has improved a lot and if you don't use the end to end encryption, it seems to be very reliable.

72 points by ementally 4y ago

ShrimpHawk 4y ago

from 2021

phneutral26 4y ago

Consider adding 2021 to the post title, for clarity. Anyhow, interesting article. Thanks for sharing.

palata 4y ago

Interesting analysis! Showing (once again) that anonymity is difficult to achieve.

tandr 4y ago

Did Signal fix the protocol, or at least responded with something?

ementally 4y ago
Nope, according to https://community.signalusers.org/t/sealed-sender-still-broken-or-already-fixed/49978 https://community.signalusers.org/t/sealed-sender-still-brok...
- wkat4242 4y ago
  That's pretty bad 2 years later..
  - tptacek 4y ago
    I guess? This is an anonymity feature no other mainstream messenger has in the first place. The idea behind sealed sender is that clients can send messages through Signal's service without authenticating directly to the server. It's not, like, part of the core E2E mechanic of Signal; I'm not even sure it was ever out of beta.
  - upofadown 4y ago
    The suggested fix was pretty complicated and had some drawbacks (see section VII-B). Signal probably did not agree that it was worth it. It's a hard problem and it just might be the case that no one has of yet come up with a workable solution.

deleted 4y ago

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  [deleted]

godelski 4y ago

FYI I don't think Signal cares much about anonymity (sadly). I've seen several discussions on their forums where admins have even been hostile to people asking for it. I love Signal, but its community is toxic and I really wish the devs would move a bit faster. I know it is a tall order, but that's what Moxie argued in his "The Ecosystem is Moving" talk (we can't have decentralized because you have to move fast and adapt). There's a lot of low hanging fruit that Signal just seems to ignore.

tptacek 4y ago
However much they care or don't care about it, the salience of this NDSS paper is that Signal has a relatively complex anonymity feature that no other mainstream messenger has (the ability to cryptographically authenticate a message that can be delivered via the service without the client authenticating to the server), and it's susceptible to some straightforward network timing analyses. There may be any number of other reasons to believe that Signal doesn't care enough about anonymity, but with respect to this paper, the most you can say is that they don't get full credit for an extra credit anonymity project they did.
- godelski 4y ago
  Oh, I use Signal and still push my friends and family to use it. I'm not arguing against it. You're right that it is still a great app that does things others don't. As to anonymity, I'm more frustrated with the community being hostile against other community members asking and pushing for it. I do understand that the community isn't the signal team, but it is their official community so it does set the tone. Especially since they specifically note that that's the only community they pay attention to. (e.g. GitHub bug reports should be on community) As for non-anonymity stuff, there are quite a lot of extremely low hanging fruit that is weirdly not available but highly asked for. Like having to go to https://signalstickers.com/ https://signalstickers.com/ to get stickers? This should clearly be accessible through the app (or they should be hosting their own). Delayed messages are thankfully here but took forever. For some reason forwarding messages on phone vs computer has different behavior (I can edit from the computer; the preferred method). Still can't find messages associated with media. Can't star/favorite messages. These are very important features that each could be done in less than a weekend so it just seems odd. I do want to see Signal be more used and I want to see it grow. I love it and advocate for it, but that also doesn't mean I'm not going to be critical of it when it is having issues.

autoexec 4y ago

My impression is that since around 2020 Signal devs have been trying as quietly as possible to tell people that the service can no longer be trusted and everyone should switch to something else. First they started keeping sensitive user data in the cloud which upset and alienated a bunch of users, they've also refused to update their privacy policy to reflect that fact, then they added the weird crypto thing which upset more users, and killing off the ability to handle SMS/MMS as well as secure communications, one of their best features, seems like yet another attempt drive away users. Maybe going years without fixing important features with known vulnerabilities is just another hint being left to ward off anyone who really needs their communications secure. I loved signal and recommended it to many people over the years, but I ditched it after they started collecting and insecurely storing user data in the cloud, and I'm still disappointed in what it has turned into. The folks behind Signal had a great project once and I hope someone outside of the US steps up to give us a real replacement one of these days.

ChuckNorris89 4y ago
Me and my family ditched Signal this week after 2 years of struggle. The calls refusing to ring on our 3 different brands of Android phones, only to be greated by a missed call notification later, despite disabling all the battery optimization features on each phone meant the app was unusable for us. It always rings on the PC app, but on our phones it's always hit or miss. Only once you open the app when someone is calling you, does it finally decide to ring. Googling around it seems many are impacted by this bug which has been around since forever, but no fix has been implemented and since the dev team seems mostly iOS focused, I doubt it will ever be. The lack of supporting linking to Android tablets is another blow for us when iPad support has been available since forever. Shame. I respect Signal and its devs for doing what they did, but we need more than a barebones messaging app with focus on stickers and stories instead of fixing jarring bugs and missing Android features, so it looks like it's back to WhatsApp for us. It may be part of Zuck's empire but it has never ever let us down in any situation.
- raybb 4y ago
  Bummer. Have you given Element a shot recently? It has improved a lot and if you don't use the end to end encryption, it seems to be very reliable.