7 ms·

SMSSecure – SMS Encryption for Android

81 points by psykovsky 12y ago

sschueller 12y ago
"This is a fork of TextSecure that aims to keep the SMS encryption that TextSecure removed for a variety of reasons." Reason for the fork: https://whispersystems.org/blog/goodbye-encrypted-sms/ https://whispersystems.org/blog/goodbye-encrypted-sms/
- AlyssaRowan 12y ago
  The underlying reasons are actually pretty sensible. Signal (as it will be) can't deliver encryption via SMS on iOS due to platform restrictions. Neither can tablets or computers normally send SMS messages. (To say nothing of metadata risks, although TextSecure cannot address that without a decoupling layer, like Tor, and in any case low-latency low-bandwidth mixnet messaging is very hard versus nation-state adversaries with traffic correlation abilities.) It's also clear that voice and video can't be delivered well or at all by SMS/MMS, and that MMS in particular is a huge pain in the arse. However, users who have limited/no data plans are up in arms. Whole bunch of 1-star reviews. Clearly quite a few vocal users (not necessarily users in regions you might expect) liked this feature, used it, seemingly needed it. I know that sometimes when travelling even I'm out of data service, but within SMS service. So it may be that a fork does make semantic sense here. Signal will eventually deliver cross-platform best-in-class secure messaging, group messaging, voice/video/etc - features which cannot be delivered by SMS - and SMSSecure could deliver encrypted SMS messages for users on the Android platform (only).
  - hobarrera 12y ago
    > Neither can tablets or computers normally send SMS messages TextSecure is android-only, so I fail to see how this is an issue. Also, (please, correct me if I'm wrong), they also require that you have an SMS-capable line to use it, so I fail to see how that limitation would matter.
  - psykovsky 12y ago
    If they intend to be a messaging app then they should stop trying to be the default SMS application. They're just another messaging app.
    - rand334 12y ago
      I've read almost all of the comments here and I'm so confused... So I'm not going to be able to text my non-TextSecure friends with it anymore? And, if my data connection drops right before I message a TextSecure user, will it get sent plaintext over SMS then?
      - psykovsky 12y ago
        I guess not, at least if you want to keep your SMS's encrypted and use SMSSecure.
    - AlyssaRowan 12y ago
      Agreed there: if Signal won't do SMS, they shouldn't be catching SMS intents, or they might get invoked when, for example, there's no data. (Of course, there's scope for disagreement here. SMS and particularly MMS are horrible, but sometimes horrible is all you've got.)
      - sarciszewski 12y ago
        Maybe someone should suggest this to the team? They probably did that from the get go, but now no longer need to.
        detaro 12y ago
        They said on Github that they are keeping it for a while, so that users still can receive encrypted SMS from users that haven't updated yet.
        sarciszewski 12y ago
        Okay, cool. Sounds like they're doing the right thing.
  - wtbob 12y ago
    > in any case low-latency low-bandwidth mixnet messaging is very hard versus nation-state adversaries with traffic correlation abilities Indeed, The Pynchon Gate[1] paper indicates that intersection attacks can break any mixnet, to include high-latency mixnet. The authors' solution is high-latency, high-bandwidth private information retrieval. Sadly, I can't see a way to make this work efficiently with mobile devices. [1] http://freehaven.net/anonbib/cache/sassaman:wpes2005.pdf http://freehaven.net/anonbib/cache/sassaman:wpes2005.pdf
dTal 12y ago
"Get it on F-Droid" - that sure is a pleasant change from TextSecure's needless drama.
- yownie 12y ago
  OMG. so much this++ I wonder how they're avoiding using GCM like textsecure was
  - psykovsky 12y ago
    I think it is because they only handle SMS's. It doesn't have the push messaging part. You still need TextSecure for that.
  - AlyssaRowan 12y ago
    I don't know - anyone got time to review the source? - but if they're only doing SMS, they might not need it; after all, SMS is already 'push', and it was only needed for push notifications for the data channel.
  - pR0Ps 12y ago
    We've removed the need for GCM since SMSSecure only deals with the SMS/MMS functionality.
- patcon 12y ago
  https://github.com/WhisperSystems/Flock/commit/9c2fa9e35ed72be31844dbc35bd4b84b60c63e0d https://github.com/WhisperSystems/Flock/commit/9c2fa9e35ed72... https://github.com/WhisperSystems/Flock/blob/master/flock/src/nonplay/java/org/anhonesteffort/flock/ApplicationContext.java#L42 https://github.com/WhisperSystems/Flock/blob/master/flock/sr... https://github.com/WhisperSystems/Flock/blob/master/flock/build.gradle#L59 https://github.com/WhisperSystems/Flock/blob/master/flock/bu... https://github.com/WhisperSystems/Flock/blob/master/flock/src/nonplay/res/values/strings.xml#L25-L27 https://github.com/WhisperSystems/Flock/blob/master/flock/sr...
darkhorn 12y ago
Last year I have started to use BABEL. https://play.google.com/store/apps/details?id=cz.oksystem.sms&hl=en https://play.google.com/store/apps/details?id=cz.oksystem.sm...
- sarciszewski 12y ago
  I don't see a link to github anywhere in the description. Is it open source?
  - JupiterMoon 12y ago
    I don't know anything about this app and don't know if it is open source (it doesn't look like it is). However, did you know that not all open source stuff is on github???
    - sarciszewski 12y ago
      > However, did you know that not all open source stuff is on github??? Yes, I did. I also looked for bitbucket, gitlab, Google Code, etc. and found nothing. So I just opened it in JD GUI and saw this gem. Cipher localCipher = Cipher.getInstance("AES/ECB/NoPadding"); Don't use BABEL. It's written by people who don't understand security. EDIT: private static final SecretKey a = new SecretKeySpec( new byte[] { -91, 63, 7, 80, 88, -58, -47, -28, 55, 126, -126, 27, 67, -64, 97, -46, 5, 44, -14, -94, -103, 96, -57, 33, -108, -104, -122, 125, 49, 29, -25, -27 }, "AES" ); Is dat a static key? :O
      - JupiterMoon 12y ago
        > Yes, I did. I also looked for bitbucket, gitlab, Google Code, etc. and found nothing. No worries then. I checked out their website - I can't see any links to source code. So in my opinion it's just yet another closed source pretending to be secure messaging service then...
      - darkhorn 12y ago
tveita 12y ago
I didn't mind much that TextSecure removed the SMS feature, since I didn't use it anyway, but I think the removal was badly handled. I'm glad someone is catering to the users who used this feature, it gets more eyes on the code and increases the pressure on the Signal team to do things right. When TextSecure removed SMS encryption there wasn't a clear warning about it in the what's new message, and as far as I can tell there was no deprecation period or warning to users who had been using it. You'd be sending encrypted messages before the update, and unencrypted messages after. For some reason they didn't link to their blog post[1] in the what's new message. It looks to me like they didn't want people to notice that they were removing a feature. This lessens my trust in the creators and makes me hesitate to update the app since I don't know if they will change or remove features I do use in the future without warning. Hopefully they'll review their process so they don't scare more people over to SMSSecure. [1] https://whispersystems.org/blog/goodbye-encrypted-sms/ https://whispersystems.org/blog/goodbye-encrypted-sms/
- classicsnoot 12y ago
  I am an avid TS user. I hate that they stopped SMS because the move is contrary to their stated goal[s]. Taking that as understood, I do not feel they mishandled notification of their stupid decision.
- moxie 12y ago
  If you didn't use the feature, you might have missed it, but we talked about its removal publicly for over a year. We also made many incremental changes over that year in order to phase it out so that it wasn't a sudden removal. We did all of that, despite the fact that it was used by an incredibly tiny fraction of our total install base. The people who used encrypted SMS are very vocal, but the users we're really targeting never even knew it existed. I think projects like this one are great. I have no idea if the people behind it know what they're doing or can write secure software, but we've always wanted some place where the people who want to import their GPG key, manually select their underlying block cipher, or support WoT style key signatures can go. Projects like these might be a better fit for those users.
  - 12y ago
ToastyMallows 12y ago
As someone who doesn't follow TextSecure or anything else, how does this work? How do my messages get encrypted, yet the people I'm texting don't need to install anything to read them? What am I missing here.
- Couto 12y ago
  Both parties need to have SMSSecure installed, and a secure session started — a roundtrip of sms to exchange keys, or something (im not an expert so not sure if those are keys, or something else). Otherwise they will only see a garbage of letters/numbers.
  - ToastyMallows 12y ago
    Ah ok, I guess I read this wrong: > SMSSecure works like any other SMS application. There's nothing to sign up for and no new service your friends need to join. Made it sound like there's nothing to install. Kind of confusing.
    - throwaway7767 12y ago
      They mean that they use the SMS infrastructure of your telco and not their own servers. You still need to do key negotiation out of band.
  - huehehue 12y ago
    That seems like it would turn off some potential users due to the hassle of switching apps. I'm ignorant of the process, but is there no way to check that the user has installed SMSSecure first and, if not, fall back to sending unencrypted data? (perhaps that could be toggled via a fail open/closed option)
    - Couto 12y ago
      You can use SMSSecure as your default messaging app. That way you don't have to switch apps. You can even import your SMS from the default messaging app so that you don't loose your history. Bonus: you can then encrypt those SMS locally, but that's optional. You can toggle the option to send encrypted sms or not, per contact, so if your contact doesn't support SMSSecure, you just send a regular SMS. The ability to know who's using SMSSecure is interesting and not currently supported (that I know of)
classicsnoot 12y ago
Is this a full replacement for TS or does it just do SMS?
- psykovsky 12y ago
  It just does SMS.
  - classicsnoot 12y ago
    I LIKE GOOGLE. DEVS ARE THE TOP TIER OF SOCIETY. APPLE IS EVIL/AWESOME. can i have my 137 score back pls?
  - classicsnoot 12y ago
    meh
  - marssaxman 12y ago
    perfect! that's all I wanted it to do anyway.
pR0Ps 12y ago
I'm one of the developers of this project. If you have any questions, let me know. To be clear, this project isn't endorsed in any way by Open Whisper Systems. We forked their codebase pre-v2.7.0 and are integrating upstream commits, but that's it. The idea isn't to compete with TextSecure, it's to provide the encrypted SMS functionality TextSecure used to (with all it's compromises and drawbacks) for people that push-based messaging isn't an option for.
- hobarrera 12y ago
  The really hard part about encrypting communications is key distribution and validation (eg: validating that the public key for number 555-1234 actually belongs to Alice). How did you guys attack this problem?
  - pR0Ps 12y ago
    Key distribution isn't really something we're doing. Each user just keeps their own list of verified identities. We're using the same system we inherited from TextSecure for encrypted SMS: Trust keys implicitly on first use, while encouraging users to verify them out of band. The verification is handled by providing a screen that has your identity and what you think the recipient's identity is. If the recipient's identity matches what your app says and vice-versa, then you know you're talking to the right person. Ideally, the verification would be done in-person or via another secure means of communication. Currently you can verify identities by just reading them out, or via QR code.
- sarciszewski 12y ago
  I remember moxie challenging people on Twitter to do exactly this a while back. So, kudos for taking up the challenge.

81 points by psykovsky 12y ago

"This is a fork of TextSecure that aims to keep the SMS encryption that TextSecure removed for a variety of reasons." Reason for the fork: https://whispersystems.org/blog/goodbye-encrypted-sms/ https://whispersystems.org/blog/goodbye-encrypted-sms/

AlyssaRowan 12y ago
The underlying reasons are actually pretty sensible. Signal (as it will be) can't deliver encryption via SMS on iOS due to platform restrictions. Neither can tablets or computers normally send SMS messages. (To say nothing of metadata risks, although TextSecure cannot address that without a decoupling layer, like Tor, and in any case low-latency low-bandwidth mixnet messaging is very hard versus nation-state adversaries with traffic correlation abilities.) It's also clear that voice and video can't be delivered well or at all by SMS/MMS, and that MMS in particular is a huge pain in the arse. However, users who have limited/no data plans are up in arms. Whole bunch of 1-star reviews. Clearly quite a few vocal users (not necessarily users in regions you might expect) liked this feature, used it, seemingly needed it. I know that sometimes when travelling even I'm out of data service, but within SMS service. So it may be that a fork does make semantic sense here. Signal will eventually deliver cross-platform best-in-class secure messaging, group messaging, voice/video/etc - features which cannot be delivered by SMS - and SMSSecure could deliver encrypted SMS messages for users on the Android platform (only).
- hobarrera 12y ago
  > Neither can tablets or computers normally send SMS messages TextSecure is android-only, so I fail to see how this is an issue. Also, (please, correct me if I'm wrong), they also require that you have an SMS-capable line to use it, so I fail to see how that limitation would matter.
- psykovsky 12y ago
  If they intend to be a messaging app then they should stop trying to be the default SMS application. They're just another messaging app.
  - rand334 12y ago
    I've read almost all of the comments here and I'm so confused... So I'm not going to be able to text my non-TextSecure friends with it anymore? And, if my data connection drops right before I message a TextSecure user, will it get sent plaintext over SMS then?
    - psykovsky 12y ago
      I guess not, at least if you want to keep your SMS's encrypted and use SMSSecure.
  - AlyssaRowan 12y ago
    Agreed there: if Signal won't do SMS, they shouldn't be catching SMS intents, or they might get invoked when, for example, there's no data. (Of course, there's scope for disagreement here. SMS and particularly MMS are horrible, but sometimes horrible is all you've got.)
    - sarciszewski 12y ago
      Maybe someone should suggest this to the team? They probably did that from the get go, but now no longer need to.
      - detaro 12y ago
        They said on Github that they are keeping it for a while, so that users still can receive encrypted SMS from users that haven't updated yet.
        sarciszewski 12y ago
        Okay, cool. Sounds like they're doing the right thing.
- wtbob 12y ago
  > in any case low-latency low-bandwidth mixnet messaging is very hard versus nation-state adversaries with traffic correlation abilities Indeed, The Pynchon Gate[1] paper indicates that intersection attacks can break any mixnet, to include high-latency mixnet. The authors' solution is high-latency, high-bandwidth private information retrieval. Sadly, I can't see a way to make this work efficiently with mobile devices. [1] http://freehaven.net/anonbib/cache/sassaman:wpes2005.pdf http://freehaven.net/anonbib/cache/sassaman:wpes2005.pdf

dTal 12y ago

"Get it on F-Droid" - that sure is a pleasant change from TextSecure's needless drama.

yownie 12y ago
OMG. so much this++ I wonder how they're avoiding using GCM like textsecure was
- psykovsky 12y ago
  I think it is because they only handle SMS's. It doesn't have the push messaging part. You still need TextSecure for that.
- AlyssaRowan 12y ago
  I don't know - anyone got time to review the source? - but if they're only doing SMS, they might not need it; after all, SMS is already 'push', and it was only needed for push notifications for the data channel.
- pR0Ps 12y ago
  We've removed the need for GCM since SMSSecure only deals with the SMS/MMS functionality.
patcon 12y ago
https://github.com/WhisperSystems/Flock/commit/9c2fa9e35ed72be31844dbc35bd4b84b60c63e0d https://github.com/WhisperSystems/Flock/commit/9c2fa9e35ed72... https://github.com/WhisperSystems/Flock/blob/master/flock/src/nonplay/java/org/anhonesteffort/flock/ApplicationContext.java#L42 https://github.com/WhisperSystems/Flock/blob/master/flock/sr... https://github.com/WhisperSystems/Flock/blob/master/flock/build.gradle#L59 https://github.com/WhisperSystems/Flock/blob/master/flock/bu... https://github.com/WhisperSystems/Flock/blob/master/flock/src/nonplay/res/values/strings.xml#L25-L27 https://github.com/WhisperSystems/Flock/blob/master/flock/sr...

darkhorn 12y ago

Last year I have started to use BABEL. https://play.google.com/store/apps/details?id=cz.oksystem.sms&hl=en https://play.google.com/store/apps/details?id=cz.oksystem.sm...

sarciszewski 12y ago
I don't see a link to github anywhere in the description. Is it open source?
- JupiterMoon 12y ago
  I don't know anything about this app and don't know if it is open source (it doesn't look like it is). However, did you know that not all open source stuff is on github???
  - sarciszewski 12y ago
    > However, did you know that not all open source stuff is on github??? Yes, I did. I also looked for bitbucket, gitlab, Google Code, etc. and found nothing. So I just opened it in JD GUI and saw this gem. Cipher localCipher = Cipher.getInstance("AES/ECB/NoPadding"); Don't use BABEL. It's written by people who don't understand security. EDIT: private static final SecretKey a = new SecretKeySpec( new byte[] { -91, 63, 7, 80, 88, -58, -47, -28, 55, 126, -126, 27, 67, -64, 97, -46, 5, 44, -14, -94, -103, 96, -57, 33, -108, -104, -122, 125, 49, 29, -25, -27 }, "AES" ); Is dat a static key? :O
    - JupiterMoon 12y ago
      > Yes, I did. I also looked for bitbucket, gitlab, Google Code, etc. and found nothing. No worries then. I checked out their website - I can't see any links to source code. So in my opinion it's just yet another closed source pretending to be secure messaging service then...
    - darkhorn 12y ago

tveita 12y ago

I didn't mind much that TextSecure removed the SMS feature, since I didn't use it anyway, but I think the removal was badly handled. I'm glad someone is catering to the users who used this feature, it gets more eyes on the code and increases the pressure on the Signal team to do things right. When TextSecure removed SMS encryption there wasn't a clear warning about it in the what's new message, and as far as I can tell there was no deprecation period or warning to users who had been using it. You'd be sending encrypted messages before the update, and unencrypted messages after. For some reason they didn't link to their blog post[1] in the what's new message. It looks to me like they didn't want people to notice that they were removing a feature. This lessens my trust in the creators and makes me hesitate to update the app since I don't know if they will change or remove features I do use in the future without warning. Hopefully they'll review their process so they don't scare more people over to SMSSecure. [1] https://whispersystems.org/blog/goodbye-encrypted-sms/ https://whispersystems.org/blog/goodbye-encrypted-sms/

classicsnoot 12y ago
I am an avid TS user. I hate that they stopped SMS because the move is contrary to their stated goal[s]. Taking that as understood, I do not feel they mishandled notification of their stupid decision.
moxie 12y ago
If you didn't use the feature, you might have missed it, but we talked about its removal publicly for over a year. We also made many incremental changes over that year in order to phase it out so that it wasn't a sudden removal. We did all of that, despite the fact that it was used by an incredibly tiny fraction of our total install base. The people who used encrypted SMS are very vocal, but the users we're really targeting never even knew it existed. I think projects like this one are great. I have no idea if the people behind it know what they're doing or can write secure software, but we've always wanted some place where the people who want to import their GPG key, manually select their underlying block cipher, or support WoT style key signatures can go. Projects like these might be a better fit for those users.
- 12y ago

ToastyMallows 12y ago

As someone who doesn't follow TextSecure or anything else, how does this work? How do my messages get encrypted, yet the people I'm texting don't need to install anything to read them? What am I missing here.

Couto 12y ago
Both parties need to have SMSSecure installed, and a secure session started — a roundtrip of sms to exchange keys, or something (im not an expert so not sure if those are keys, or something else). Otherwise they will only see a garbage of letters/numbers.
- ToastyMallows 12y ago
  Ah ok, I guess I read this wrong: > SMSSecure works like any other SMS application. There's nothing to sign up for and no new service your friends need to join. Made it sound like there's nothing to install. Kind of confusing.
  - throwaway7767 12y ago
    They mean that they use the SMS infrastructure of your telco and not their own servers. You still need to do key negotiation out of band.
- huehehue 12y ago
  That seems like it would turn off some potential users due to the hassle of switching apps. I'm ignorant of the process, but is there no way to check that the user has installed SMSSecure first and, if not, fall back to sending unencrypted data? (perhaps that could be toggled via a fail open/closed option)
  - Couto 12y ago
    You can use SMSSecure as your default messaging app. That way you don't have to switch apps. You can even import your SMS from the default messaging app so that you don't loose your history. Bonus: you can then encrypt those SMS locally, but that's optional. You can toggle the option to send encrypted sms or not, per contact, so if your contact doesn't support SMSSecure, you just send a regular SMS. The ability to know who's using SMSSecure is interesting and not currently supported (that I know of)

classicsnoot 12y ago

Is this a full replacement for TS or does it just do SMS?

psykovsky 12y ago
It just does SMS.
- classicsnoot 12y ago
  I LIKE GOOGLE. DEVS ARE THE TOP TIER OF SOCIETY. APPLE IS EVIL/AWESOME. can i have my 137 score back pls?
- classicsnoot 12y ago
  meh
- marssaxman 12y ago
  perfect! that's all I wanted it to do anyway.

pR0Ps 12y ago

I'm one of the developers of this project. If you have any questions, let me know. To be clear, this project isn't endorsed in any way by Open Whisper Systems. We forked their codebase pre-v2.7.0 and are integrating upstream commits, but that's it. The idea isn't to compete with TextSecure, it's to provide the encrypted SMS functionality TextSecure used to (with all it's compromises and drawbacks) for people that push-based messaging isn't an option for.

hobarrera 12y ago
The really hard part about encrypting communications is key distribution and validation (eg: validating that the public key for number 555-1234 actually belongs to Alice). How did you guys attack this problem?
- pR0Ps 12y ago
  Key distribution isn't really something we're doing. Each user just keeps their own list of verified identities. We're using the same system we inherited from TextSecure for encrypted SMS: Trust keys implicitly on first use, while encouraging users to verify them out of band. The verification is handled by providing a screen that has your identity and what you think the recipient's identity is. If the recipient's identity matches what your app says and vice-versa, then you know you're talking to the right person. Ideally, the verification would be done in-person or via another secure means of communication. Currently you can verify identities by just reading them out, or via QR code.
sarciszewski 12y ago
I remember moxie challenging people on Twitter to do exactly this a while back. So, kudos for taking up the challenge.