iPhone Text Message Forwarding security
Text Message Forwarding automatically sends SMS text messages received on an iPhone to a user’s enrolled iPad or Mac. Each device must be signed in to the iMessage service using the same Apple Account. When Text Message Forwarding is turned on, enrolment is automatic on devices within a user’s circle of trust if two-factor authentication is enabled. Otherwise, enrolment is verified on each device by entering a random six-digit numeric code generated by iPhone.
After devices are linked, iPhone encrypts and forwards incoming SMS text messages to each device, utilising the methods described in iMessage security overview. Replies are sent back to iPhone using the same method and then iPhone sends the reply as a text message using the network provider’s SMS transmission mechanism. Text Message Forwarding can be turned on or off in Messages settings.