Apple APNS Data Transfer Encryption

Apple Push Notification Service (APNS) is a robust and highly efficient service for sending secure data to devices running on the iOS operating system. Each device establishes an accredited and encrypted IP connection with the service and receives notifications over this persistent connection. If a notification for an application arrives when that application is not running, the device alerts the user that the application has data waiting for it.

APNS includes a default Quality of Service (QoS) component that performs a store-and-forward function. If APNS attempts to deliver a message when the device is offline, the QoS stores the notification. It retains only one notification per application on a device: the last notification received from a provider for that application. When the offline device later reconnects, the QoS forwards the stored notification to the device. The QoS retains a notification for a limited period before deleting it.