iMessage encryption - multiple sends?

[Scorch07]

So I've been educating myself on security and just generally learning how things work. I pretty well understand how iMessage encryption work with Apple servers passing out the public key for a given device and the private key never leaving said device.

That said - say I have an iPhone, iPad, and a Mac. My understanding is that each has a key pair. Does that mean when someone sends me an iMessage, the device that they send it from makes three copies and individually each one and sends it out? I guess that's the only way that seems secure, but it also seems a little tricky.

In all honesty this question has no practical application, I was just curious how it all works.

 

[electronicsguy]

The sender device only makes 1 copy, to be sent to icloud server. It's the server which will make number of copies, based on how many active devices the receiver has. The sender has not idea of this.

 

[Scorch07]

The sender device only makes 1 copy, to be sent to icloud server. It's the server which will make number of copies, based on how many active devices the receiver has. The sender has not idea of this.

But wouldn't that mean the Apple server has to be able to manipulate/"see" the message in order to encrypt it for the receiver? Or is it some kind of double encryption (One general encryption, and then encrypted again for the specific device once it gets to Apple)?

 

[electronicsguy]

But wouldn't that mean the Apple server has to be able to manipulate/"see" the message in order to encrypt it for the receiver? Or is it some kind of double encryption (One general encryption, and then encrypted again for the specific device once it gets to Apple)?

no. all it means that Apple servers know who the recipient is. Which obviously any messaging service needs to. It simply forwards your encrypted message. The "metadata" which is sender, receiver addresses are not encrypted.