4 ms·

I could be wrong, but he just puts the sender phone in Airplane mode and then sends a few messages. Then he swaps the sim card from the receivers "Laura's" phon

I could be wrong, but he just puts the sender phone in Airplane mode and then sends a few messages. Then he swaps the sim card from the receivers "Laura's" phone to the government's phone. Then the government's phone is able to view the messages sent while the sender's phone was in Airplane mode. Is that really the vulnerability?

mike-cardwell 10y ago
The governments phone doesn't have Laura's private key on it. It is not transferred when the SIM is transferred. So even without the private key, they can intercept the messages. [edit] Also, even if Lauras phone wasn't in airplane mode, all they need to do is prevent the delivery reports, then they can repeat the trick. And of course, they don't need the SIM in order to take over the phone number.
- nodesocket 10y ago
  I get that the Government's phone does not have Laura's private key. What does Airplane mode have to do with it though? Does this exploit only work when messages are sent unconfirmed/no-network from the sender's phone?
  - y7 10y ago
    Yes. It only works when the original recipient is offline (when they come back online it can be detected).
    - mike-cardwell 10y ago
      Or when the original recipient is not offline, but has been targeted for an attack so their delivery reports are getting blocked.
Buge 10y ago
Yes it's a real vulnerability. Edward's phone is reencrypting the message with a new (malicious) public key without Edward's permission. It's not clear this would be a very practical attack, but it's definitely something that Whatsapp should stop if the extra security mode is enabled.
- nodesocket 10y ago
  I get it, but let's stop calling it a backdoor conspiracy theorists. It is really a UX decision. WhatsApp decided they'd rather not have the possibility of losing messages when you switch phones. I see the fix as being as easy as a new security preference that by default behaves the same way, but you have the option to prevent sending messages that are not reported as delivered to a new device/key. Essentially those messages get lost.
  - feld 10y ago
    You can't prove whether or not it was intentional. Marketing speak can spin this as a convenience for the user. It's still a backdoor until they fix this. I don't believe Moxie has the actual insight into Facebook's true intentions with the Whatsapp platform. He may believe their intentions are honest, but he's just a cog in their wheel. If he honestly believed Whatsapp was sufficiently secure why would he bother with Signal?
    - FabHK 10y ago
      It was intentional, they've thought about it. Yes, of course it is clearly less secure than Signal. It's an UI tradeoff given the reality that the vast majority of the billion+ WhatsApp users will not verify key fingerprints ("security number", I believe, in Signal speak) out of band. Again, let me quote Moxie from the other thread: "Given that reality, the most important thing is to design your product so that the server has no knowledge of who has verified keys or who has enabled a setting to see key change notifications. That way the server has no knowledge of who it can MITM without getting caught. I've been impressed with the level of care that WhatsApp has given to that requirement." https://news.ycombinator.com/item?id=13394900 https://news.ycombinator.com/item?id=13394900 The point is, if you need the extra security, use Signal, Threema. But if you want to get good crypto in the hands of billions, make it simple and invisible. That's what they've aimed for, and achieved.

mike-cardwell 10y ago

The governments phone doesn't have Laura's private key on it. It is not transferred when the SIM is transferred. So even without the private key, they can intercept the messages. [edit] Also, even if Lauras phone wasn't in airplane mode, all they need to do is prevent the delivery reports, then they can repeat the trick. And of course, they don't need the SIM in order to take over the phone number.

nodesocket 10y ago
I get that the Government's phone does not have Laura's private key. What does Airplane mode have to do with it though? Does this exploit only work when messages are sent unconfirmed/no-network from the sender's phone?
- y7 10y ago
  Yes. It only works when the original recipient is offline (when they come back online it can be detected).
  - mike-cardwell 10y ago
    Or when the original recipient is not offline, but has been targeted for an attack so their delivery reports are getting blocked.

Buge 10y ago

Yes it's a real vulnerability. Edward's phone is reencrypting the message with a new (malicious) public key without Edward's permission. It's not clear this would be a very practical attack, but it's definitely something that Whatsapp should stop if the extra security mode is enabled.

nodesocket 10y ago
I get it, but let's stop calling it a backdoor conspiracy theorists. It is really a UX decision. WhatsApp decided they'd rather not have the possibility of losing messages when you switch phones. I see the fix as being as easy as a new security preference that by default behaves the same way, but you have the option to prevent sending messages that are not reported as delivered to a new device/key. Essentially those messages get lost.
- feld 10y ago
  You can't prove whether or not it was intentional. Marketing speak can spin this as a convenience for the user. It's still a backdoor until they fix this. I don't believe Moxie has the actual insight into Facebook's true intentions with the Whatsapp platform. He may believe their intentions are honest, but he's just a cog in their wheel. If he honestly believed Whatsapp was sufficiently secure why would he bother with Signal?
  - FabHK 10y ago
    It was intentional, they've thought about it. Yes, of course it is clearly less secure than Signal. It's an UI tradeoff given the reality that the vast majority of the billion+ WhatsApp users will not verify key fingerprints ("security number", I believe, in Signal speak) out of band. Again, let me quote Moxie from the other thread: "Given that reality, the most important thing is to design your product so that the server has no knowledge of who has verified keys or who has enabled a setting to see key change notifications. That way the server has no knowledge of who it can MITM without getting caught. I've been impressed with the level of care that WhatsApp has given to that requirement." https://news.ycombinator.com/item?id=13394900 https://news.ycombinator.com/item?id=13394900 The point is, if you need the extra security, use Signal, Threema. But if you want to get good crypto in the hands of billions, make it simple and invisible. That's what they've aimed for, and achieved.