iMessage doesn't share private keys between devices. Each device has its own secret key, and when you send a message to a person with multiple devices, you encr

iMessage doesn't share private keys between devices. Each device has its own secret key, and when you send a message to a person with multiple devices, you encrypt multiple copies, one for each (source: https://support.apple.com/guide/security/how-imessage-sends-and-receives-messages-sec70e68c949/1/web/1 https://support.apple.com/guide/security/how-imessage-sends-...) An issue here is that the software doesn't show the user the list of keys used to encrypt a given message. If an attacker can inject their own keys into the identity service records for a given user, they would then receive a copy of all messages sent to that user.