US Patent 7539313 System and method for key management across geographic domains

A method for managing encryption keys in a communication system having a plurality of communication devices includes establishing a set of cryptographic keys for secure communication. Each of the cryptographic keys is associated with a geographic region. A geographic region is determined for a communication device and at least one cryptographic key is distributed to the communication device based on the geographic region of the communication device. At least one cryptographic key may be used to derive further cryptographic keys associated with a set of sub-regions of the geographic region associated with the communication device.