Patent ID: 8713317

Claim:
A method for encrypting data by a first node in a wireless communication system, the method comprising: performing an authentication operation with a second node, by the first node, using a first encryption key generated using a plurality of encryption key parameters, the plurality of encryption key parameters including an authentication key, a first random number, and at least one of a counter value, a security association identity (SAID), a first node IDentifier (ID), and a second node ID; changing, by the first node, the first random number to generate a second encryption key being identical to the first encryption key, if the authentication key is changed during a re-authentication operation performed between the first node and the second node; generating, by the first node, the second encryption key using the changed authentication key, the changed first random number, and at least one of the counter value, the SAID, the first node ID and the second node ID; and encrypting, by the first node, data to be transmitted to the second node using the second encryption key.