International Business Machines Corporation

Eliane D Bello

Frederic J Bauchot

David Frederick Bantz

Hugo M Krawczyk

Shay Kutten

Amir Herzberg

Yishay Mansour

Francois LeMaut

Marcelo Ferraz

Bernardo Da Silva Araujo Tavares

Ernesto Antunes

In a communications system comprising a number of base stations, each base station communicating over a shared communication channel with a plurality of registered stations and controlling the network cell formed by said plurality of registered stations, a method is described for dynamically registering and deregistering mobile stations. Each station owns a unique address and is allocated a local identifier at registration time. Each network cell owns a unique cell identifier known to all registered stations belonging to this network cell. Base stations manage cell members data uniquely associating the unique address and the local identifier corresponding to each one of the mobile stations belonging to their network cell. A registration request is sent to a selected base station by a registering mobile station, comprising the unique cell identifier of the network cell controlled by the selected base station and the unique address of the registering mobile station; the selected base station detects in its cell members data any conflicting registered station whose unique address matches the unique address of the registering mobile station and sends an address check packet to any conflicting registered station, comprising the unique address of the conflicting registered station, its local identifier and the identifier of the network cell it controls. A receiving registered mobile station sends to the selected base station, an acknowledgement to the address check packet if its unique address, the local identifier of its owning base station and its network cell identifier all match with the ones carried by the address check packet. The selected base station rejects the registration request it it receives an acknowledgement to its address check packet. The same address check packet is used to deregister inactive stations.

Dynamic user registration method in a mobile communications network

In a communications system, a method is described allowing two users having established a communication session identified by a unique session freshness proof, to transmit and validate a new value of a variable by using an exchange certificate which combines the following elements: the new value of the variable, a common secret key known by both users, an exchange counter representative of the number of values of said variable transmitted between the two users during the current communication session and a session freshness proof. Protection against potential eavesdroppers and intruders is provided by combining cryptographically the elements of the exchange certificate. Further protection is obtained by interrupting the current communication session and opening a new one characterized by a new unique session freshness proof when the exchange counter reaches its maximum value; thus avoiding the risk that the same value of the session freshness keeps being used when the exchange counter is reset to its initial value. Consequently a given pair of values of the session freshness proof and of the exchange counter will never be used more than one time, making eavesdropping and, replaying attacks from intruders more difficult. Preferably, the method used for opening a new communication session uses already known authentication methods based on the common secret key.

Exchange certificate for one way validation of information

A wireless Local Area Network (LAN), in which each wireless adapter includes a controller and a transceiver which are located a finite distance from each other. Each controller and transceiver has their own hop clock and hop table. A data interface which includes a command set is defined between the controller and the transceiver. The command set includes commands and procedures for synchronizing the hop clocks and hop tables between the controller and the transceiver.

Command set and procedure for synchronization of frequency hopping

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Jardim Flamboyant Campinas, Brazil

Eliane D Bello