Final answer:
The unique 64-bit identifier for a 4G mobile device is known as the International Mobile Equipment Identity (IMEI). It helps in determining the legitimacy of devices and combating theft by allowing network providers to track and manage devices on their network.
Step-by-step explanation:
The 4G mobile device has a globally unique 64-bit identifier called the International Mobile Equipment Identity (IMEI). The IMEI is a serial number that uniquely identifies a mobile device on a network. It's used for various purposes, such as determining the legitimacy of a device and helping in efforts to combat theft. When a phone is reported stolen, its IMEI can be blacklisted by networks, making the device unusable. IMEIs are essential for maintaining the security and integrity of mobile networks, allowing network providers to keep track of all active devices and ensure that communication is both efficient and secure. The structure of an IMEI includes information such as the origin, model, and serial number of the device.