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iMessage has end to end encryption and supports multiple devices. Each device uses its own keypair and when a message is sent, it is sent encrypted for each of

iMessage has end to end encryption and supports multiple devices. Each device uses its own keypair and when a message is sent, it is sent encrypted for each of the recipient's devices. https://www.apple.com/business/docs/iOS_Security_Guide.pdf https://www.apple.com/business/docs/iOS_Security_Guide.pdf

samat 10y ago
The hard part is how do you manage a list of trusted devices. The thing which is really sad is that there are no end to end encrypted group chats.
- pfg 10y ago
  > The thing which is really sad is that there are no end to end encrypted group chats. In iMessage specifically, or in general? WhatsApp/Signal do use E2E-crypto for group chats.
- 16 10y ago
  https://riot.im https://riot.im is doing this. e2e is in beta still, but they have key list management/verification in place already.
sleepychu 10y ago
How do I find out that my recipient has a new device/public key that they'd like me to encrypt with? If it's because Apple tells me so then I think can see that the end to end encryption is broken and interception is possible. Are old messages re-encrypted with the new key? This would be even worse.
- pfg 10y ago
  iMessage does not allow for any out-of-band key verification. It's correct that that Apple (and anyone compromising them) is in a position to change the recipient's key or add new ones without the sender noticing anything's going on. I think iMessage limits this to new messages. (I believe syncing is done through iCloud, which doesn't use E2E-crypto but is optional.) It would still be possible to implement this in a secure way (including out-of-band key verification) by having the "original" key (the one you've compared out-of-band) sign keys for new devices and have the server deliver that signature (which the sender can then verify). I don't know if there are any implementations of this.

samat 10y ago

The hard part is how do you manage a list of trusted devices. The thing which is really sad is that there are no end to end encrypted group chats.

pfg 10y ago
> The thing which is really sad is that there are no end to end encrypted group chats. In iMessage specifically, or in general? WhatsApp/Signal do use E2E-crypto for group chats.
16 10y ago
https://riot.im https://riot.im is doing this. e2e is in beta still, but they have key list management/verification in place already.

sleepychu 10y ago

How do I find out that my recipient has a new device/public key that they'd like me to encrypt with? If it's because Apple tells me so then I think can see that the end to end encryption is broken and interception is possible. Are old messages re-encrypted with the new key? This would be even worse.

pfg 10y ago
iMessage does not allow for any out-of-band key verification. It's correct that that Apple (and anyone compromising them) is in a position to change the recipient's key or add new ones without the sender noticing anything's going on. I think iMessage limits this to new messages. (I believe syncing is done through iCloud, which doesn't use E2E-crypto but is optional.) It would still be possible to implement this in a secure way (including out-of-band key verification) by having the "original" key (the one you've compared out-of-band) sign keys for new devices and have the server deliver that signature (which the sender can then verify). I don't know if there are any implementations of this.