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Well, there are two options: notification option and confirmation option. Moxie correctly assumes that confirmation option (require manual confirmation to res

Well, there are two options: notification option and confirmation option. Moxie correctly assumes that confirmation option (require manual confirmation to resend if key changes) should either be enabled for everyone or disabled for everyone, as its state can be determined passively by the server. But it depends on the notification option. His conclusion is that confirmation option should be disabled for everyone because if it is enabled, it is possible to leak notification option state. But it is wrong. More secure solution exists: enable notification option for everyone, and then enable confirmation option for everyone. I was complaining about why notification should be an option. Even worse, disabled by default. Wire [0] just shows "resend" button near message when it is not delivered and always shows notifications about key changes if you have verified devices. You can still ignore verification option if you want and get no notifications. Signal blocks with a message when key changes. Both solutions are secure, Wire's is more convenient, Signal is less error-prone. WhatsApp solution is simply insecure. [0] https://wire.com/ https://wire.com/

mos_basik 10y ago
>But it depends on the notification option. Ahhhh, dependencies. You're right. This is more involved than I originally thought. Here, does the following look like an accurate summary of the situation? (For optional row/cols, "Optional (yes)" with a value of "secure" means "if the feature is optional, it's secure for users who have it enabled.") Confirmation: Required Disabled Optional (yes) Optional (no) | :------: | :--------: | :------------: | :-----------: | Required | secure | secure | secure | insecure | | (Signal) | (Wire) | | | | :------: | :--------: | :------------: | :-----------: | Notification: Disabled | secure | insecure | secure | insecure | | :------: | :--------: | :------------: | :-----------: | Optional (yes) | secure | secure | insecure | secure | | | (WhatsApp) | | | | :------: | :--------: | :------------: | :-----------: | Optional (no) | secure | insecure | insecure | insecure | | | (WhatsApp) | | | | :------: | :--------: | :------------: | :-----------: |
- ycmbntrthrwaway 10y ago
  If both notification and confirmation are optional and enabled, it is secure. And I don't think WhatsApp is secure for anyone with its permanently disabled confirmation. Maybe it prevents mass surveillance, but it is still vulnerable to targeted attack. Surely it may cost facebook reputation and the attack will be detected in the end, but it is still possible.

mos_basik 10y ago

>But it depends on the notification option. Ahhhh, dependencies. You're right. This is more involved than I originally thought. Here, does the following look like an accurate summary of the situation? (For optional row/cols, "Optional (yes)" with a value of "secure" means "if the feature is optional, it's secure for users who have it enabled.") Confirmation: Required Disabled Optional (yes) Optional (no) | :------: | :--------: | :------------: | :-----------: | Required | secure | secure | secure | insecure | | (Signal) | (Wire) | | | | :------: | :--------: | :------------: | :-----------: | Notification: Disabled | secure | insecure | secure | insecure | | :------: | :--------: | :------------: | :-----------: | Optional (yes) | secure | secure | insecure | secure | | | (WhatsApp) | | | | :------: | :--------: | :------------: | :-----------: | Optional (no) | secure | insecure | insecure | insecure | | | (WhatsApp) | | | | :------: | :--------: | :------------: | :-----------: |

ycmbntrthrwaway 10y ago
If both notification and confirmation are optional and enabled, it is secure. And I don't think WhatsApp is secure for anyone with its permanently disabled confirmation. Maybe it prevents mass surveillance, but it is still vulnerable to targeted attack. Surely it may cost facebook reputation and the attack will be detected in the end, but it is still possible.