Method for using access anthorization speification in wireless insertion network and safety roaming method

An encryption key distribution method capable of performing fast roaming by differentially distributing encryption keys in advance, according to access authorization classes, in a wireless access network and a roaming method using distributed encryption keys are provided. The encryption key distribution method comprises: receiving a command to communicate with an access point not available for communication using an encryption key currently selected in the encryption key set; determining access authorization of the access point not available for communications; selecting an encryption key from the encryption key set obtained in advance corresponding to the determined access authorization; and using the selected encryption key to encrypt a transmission message and communicate with the access point not available for communication. The method reduces the delay time, which is caused by encryption key distribution while a wireless terminal is traveling, such that roaming and a hand-off are carried out quickly and safely, and user convenience and safe transmission of data are achieved.