5 ms·
Private keys, not public; the messages are decryptable by anyone who's been added to the keybag, you've probably seen the pop up notifying you that another devi
by danielsju6 14y ago
Private keys, not public; the messages are decryptable by anyone who's been added to the keybag, you've probably seen the pop up notifying you that another device (private keys burnt onto the chipset) is joining the keybag. Once you hit OK Apple pings you with encrypted communications from the other devices (them being the pipe and presumably not in the trust chain, this explains why sometimes it's a little iffy showing cross device messages.)
The protocol hasn't been completely reverse engineered but enough to know it's likely decentralized like this, just MITM it (quite a bit is documented on the wiki I linked), Apple is the CA and the piping but it appears to be rather strong and decentralized in terms of chain-of-trust. Apple has put itself, probably without coincidence, in a position where they may not even be able to execute a court order to spy on a user.
The Apple security white-papers detail their hardware level certificates, I've dealt with this a lot as a Apple MDM developer.
- deleted 14y ago[deleted]
- andreyf 14y agoI've seen the message notifying me that I've added a new device to the account, yes, but what does that have anything to do with the encryption? When someone sends me an iMessage, their client sends as many copies as I have devices?
- wyager 14y ago>When someone sends me an iMessage, their client sends as many copies as I have devices? Generally how this works is that the sender encrypts the message with a symmetric encryption algorithm (like AES) and then encrypts the randomly-generated AES key with RSA with each of the receivers' private keys. So you only send out a single message, but it can be decrypted by any of the intended recipients.
- andreyf 14y agoThat makes a lot of sense. In that case, it seems the easiest way to wiretap an iMessage account would be to compromise one of the devices. Not surprising that the DEA doesn't have that kind of expertise/authority, though.
- sneak 14y agoNope - all they have to do is get Apple to add another surveillance key to the list of device keys associated with your Apple ID. Then all future iMessages get encrypted to that one, too.
- sdoering 14y agoAnd apple would only have to make sure, that you get no warning, that another device was added to your keybag.
- sneak 14y agoThey manufacture the hardware, design and produce the software, and are the intermediary between all device communication with all other devices. I have a feeling they could manage.
- sdoering 14y agoI didn't mean to imply, that they could not, written it missed my ironic voice-modulation ;-) I really had thought, that this would have happened long ago, for everybody, and so on. Would not have thought, that this was a problem for law enforcement, as it was with i.e. skype.
- wyager 14y agoWhenever any iDevice downloads a new keybag with an extra key, it gives the user like 15 notifications that a new device has been added to the iMessage account. I don't think there's a way to suppress this (without releasing a new OS).
- konker42 14y agoIf I understand this correctly, you're saying that they actually encrypt the message with a single key. Then they encrypt the messages key with the public key of all recipients and send it with the message, so each user can decrypt the message key with the private physically attached to the device and use it to decrypt the message?
- Groxx 14y agoNot sure I'm reading this correctly, so a quick check: When I have A, and want to add B, A ships its private key to B so it can decrypt the messages too? (and vise versa, obviously) Or does A get B's public key, and A then re-encrypts and re-sends messages it receives to B? Or is it something completely different?
- andreyf 14y agoThe messages don't always arrive in the same order between the devices, so it's definitely not passed from one to the other. I imagine the senders encrypt the message with every public key in your keybag. Someone who actually knows should weigh in, though. GP's understanding seems a bit murky to me.
- Groxx 14y agoIf that's the case though, where would this popup be appearing from? (I haven't seen it, not quite sure where it would be) I would guess they wouldn't be asking the sender to approve adding my multiple computers whenever I add one, since that would be a fairly crummy user experience. Seems like it should be something that I, the owner of the receiving devices, would approve or deny.
- andreyf 14y agoThe popup (and e-mail) only notify you that a device has been added to your account. The approval is done by logging in with your Apple ID.