3 ms·

To be clear: This is not meant as a direct attack, just to highlight some of the pitfalls of creating your own e2ee chat protocol. I had a quick look at your a

To be clear: This is not meant as a direct attack, just to highlight some of the pitfalls of creating your own e2ee chat protocol. I had a quick look at your app's e2ee and summarized my findings here: https://telegra.ph/Reviewing-the-app-behind-My-small-revenge-on-Apple-security-08-04 https://telegra.ph/Reviewing-the-app-behind-My-small-revenge... Feel free to correct.

collaborative 5y ago
Hey, just seen this now. First of all, thank you for taking your time to do this. I still wish you'd told me before so that I could help you understand a few points before publishing, but I totally get it, good effort. A bit unfortunate that your post got flagged and taken down A few comments: > chat keys are ever changed or when (forward secrecy) Yes, this can be done anytime by any user. Chats -> Settings -> Renew RSA Keys The Windows client doesn't include any chat capability, it's not just that it isn't E2EE, you simply can't send/receive messages on it. I plan on replacing the Windows client entirely with a web version, it's only there for some few users who really need it >it's legal to have a directory of all registered users and email addresses accessible to all users This is not the case. Users can only see other people's contact details when they are in the same "Group". Otherwise, both email address and name is hidden >On Android, the standard `Random` is not entirely[5] based on current system time, but it does not seem like Codename One uses that. The documentation says it's purely time-based. I think you may have missed that every message is encrypted with the ChatKey but also with a different IV each time. This ensures each message originates from a different seed Don't know if you can update your post with this info? Anyway, thanks again and happy to discuss! I might have missed some points. Tbh the E2EE chat isn't really used by loads of people and in retrospective I should have made it non-E2E since most users use the app for its organigrams and not for secure comms. I just did it this way for fun Edit: One last note >If you're going to use a closed-source E2EE chat application, you might as well use WhatsApp The problem with Whatsapp is backups. They kind of make E2E pointless Edit 2: feel free to reply directly to javierantonf@hotmail.com I can't guarantee I will see your msg here Edit 3: Isn't 2048 valid until 2023 and possibly beyond?
collaborative 5y ago
I also noticed that you created your HN user to post just this, and the telegrap.ph link doesn't allow comments (nor show who you are). Given that you've decided to publish this without asking first if it's correct, I'd appreciate that you either make a reference to this item on HN or amend the specific points I mentioned. I noticed some E2E error messages coming from the trace which means that you (I assume it was you) have been tinkering with it/trying to break it. This is fine, and if you manage to do that, power to you. But if you fail to compromise the encryption then please also consider being a bit less harsh in your conclusion (considering what I've told you) Finally, I am happy to let you have a peek at the source code if you want to know more about it. I want to OS it but can't get around my paranoia of doing so. You'd just have to make your identity known and offer an email address or similar
collaborative 5y ago
I have now fixed the one vulnerability you got right (MITM): https://www.groupsapp.online/post/improved-e2e-encryption https://www.groupsapp.online/post/improved-e2e-encryption

collaborative 5y ago

Hey, just seen this now. First of all, thank you for taking your time to do this. I still wish you'd told me before so that I could help you understand a few points before publishing, but I totally get it, good effort. A bit unfortunate that your post got flagged and taken down A few comments: > chat keys are ever changed or when (forward secrecy) Yes, this can be done anytime by any user. Chats -> Settings -> Renew RSA Keys The Windows client doesn't include any chat capability, it's not just that it isn't E2EE, you simply can't send/receive messages on it. I plan on replacing the Windows client entirely with a web version, it's only there for some few users who really need it >it's legal to have a directory of all registered users and email addresses accessible to all users This is not the case. Users can only see other people's contact details when they are in the same "Group". Otherwise, both email address and name is hidden >On Android, the standard `Random` is not entirely[5] based on current system time, but it does not seem like Codename One uses that. The documentation says it's purely time-based. I think you may have missed that every message is encrypted with the ChatKey but also with a different IV each time. This ensures each message originates from a different seed Don't know if you can update your post with this info? Anyway, thanks again and happy to discuss! I might have missed some points. Tbh the E2EE chat isn't really used by loads of people and in retrospective I should have made it non-E2E since most users use the app for its organigrams and not for secure comms. I just did it this way for fun Edit: One last note >If you're going to use a closed-source E2EE chat application, you might as well use WhatsApp The problem with Whatsapp is backups. They kind of make E2E pointless Edit 2: feel free to reply directly to javierantonf@hotmail.com I can't guarantee I will see your msg here Edit 3: Isn't 2048 valid until 2023 and possibly beyond?

collaborative 5y ago

I also noticed that you created your HN user to post just this, and the telegrap.ph link doesn't allow comments (nor show who you are). Given that you've decided to publish this without asking first if it's correct, I'd appreciate that you either make a reference to this item on HN or amend the specific points I mentioned. I noticed some E2E error messages coming from the trace which means that you (I assume it was you) have been tinkering with it/trying to break it. This is fine, and if you manage to do that, power to you. But if you fail to compromise the encryption then please also consider being a bit less harsh in your conclusion (considering what I've told you) Finally, I am happy to let you have a peek at the source code if you want to know more about it. I want to OS it but can't get around my paranoia of doing so. You'd just have to make your identity known and offer an email address or similar

collaborative 5y ago

I have now fixed the one vulnerability you got right (MITM): https://www.groupsapp.online/post/improved-e2e-encryption https://www.groupsapp.online/post/improved-e2e-encryption