Far field telemetry communication with a medical device during a recharge session where a prior pairing with the medical device may not exist

A method of operation of an implantable medical device, comprising:

• receiving a recharge session key at the implantable medical device from an external device that is not program bonded to the implantable medical device via an identifier and a programming session key;
• providing the identifier from the implantable medical device to the external device;
• receiving recharge energy at the implantable medical device during a recharge session using a recharge circuit;
• exchanging information related to the recharge session but not information for secure features of the implantable medical device with the external device using the recharge session key for encryption of the information related to the recharge session being exchanged via a far field telemetry circuit while the programming session key remains stored in a memory of the implantable medical device;
• and
• at times other than during the recharge session, exchanging programming information with a second external device that is program bonded to the implantable medical device using the programming session key for encryption of the programming information being exchanged via the far field telemetry circuit and also exchanging the information for secure features with the second external device that is program bonded to the implantable medical device.

A system comprising:

• a first external device;
• a second external device;
• and
• an implantable medical device that comprises:
• a memory storing information about secure features and also storing an identifier and a programming session key that program bond the implantable medical device to the second external device;
• a recharge circuit;
• a battery coupled to the recharge circuit;
• a far field telemetry circuit;
• and
• a processor configured to receive a recharge session key from the first external device, provide the identifier to the first external device, receive recharge energy during a recharge session using the recharge circuit, exchange information related to the recharge session with the first external device using the recharge session key for encryption of the information related to recharge being exchanged via the far field telemetry circuit while the programming session key remains stored in the memory, and at times other than during the recharge session exchange programming information with the second external device using the programming session key for encryption of the programming information being exchanged via the far field telemetry circuit and also exchange the information for secure features with the second external device that is program bonded to the implantable medical device.