Patent ID: 8243928

Claim:
An authentication method in a communication system, comprising: generating and providing, at a first portable device, a first random number and a first timestamp to a first universal subscriber identity module (USIM) included in the first portable device when an authenticated communication request is detected; calculating and providing, at the first USIM, a first sign for the first portable device using the first random number and the first timestamp to the first portable device; requesting, by the first portable device, authentication for the authenticated communication by transmitting the first random number, the first timestamp, and the first sign to a second portable device; generating, at the second portable device, a second random number and a second timestamp when the first timestamp is effective, and providing the first random number, the second random number, the first timestamp, the second timestamp, and the first sign to a second USIM included in the second portable device; generating, at the second USIM, a second sign for the second portable device and a second personal key for the authenticated communication using the second random number and the second timestamp when the first random number, the first timestamp, and the first sign are effective, and providing the second sign and the second personal key to the second portable device; providing, by the second portable device, the second random number, the second timestamp, and the second sign to the first portable device; providing, at the first portable device, the second random number, the second timestamp, and the second sign to the first USIM when the second timestamp is effective; and generating and providing, at the first USIM a first personal key for the authenticated communication to the first portable device when the second sign is effective.