The public network key can be freely used by anyone. As this network is open to anyone, it offers no privacy: anyone can listen to data in a public network. It is ideal for development and evaluation.
Managed network keys are intended for companies who wish to interoperate across an industry sector. An example of a managed network is the ANT+ network. Along with the use of a managed network key, devices in a managed network must conform to specifications of channel parameters and data format (device profiles), for interoperability. A managed network key provides an added level of security, since only devices within the managed network are able to receive data from other devices in the network.
A private network key provides the greatest level of security, and is suitable for proprietary applications where interoperability is not required or desirable. A private network key provides full control over who can join the network and who can not; it also offers flexibility in terms of defining your own channel parameters and data format. Anyone with a private network key has total control over the network and can select who gets the key.
Both managed and private network keys are assigned by Garmin Canada Inc. and have an associated fee.