Electrical computers and digital processing systems: support – Multiple computer communication using cryptography – Protection at a particular protocol layer
Reexamination Certificate
1998-09-08
2001-12-25
Peeso, Thomas R. (Department: 2132)
Electrical computers and digital processing systems: support
Multiple computer communication using cryptography
Protection at a particular protocol layer
C380S247000, C380S259000, C380S278000
Reexamination Certificate
active
06334185
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to the encryption of communications between a mobile station and a network, and more particularly, to a method and apparatus for encryption between a mobile switching center node and a packet mobile switching center node utilizing an encryption algorithm stored only on a single node.
2. Description of Related Art
In a mobile cellular communications system the information which is transmitted between the network and a mobile station (MS) must be protected from undesired interception. This is accomplished by encrypting transmissions sent over the air interface between the mobile station and the network. This is normally accomplished by using some type of encryption algorithm which is executed between the network and the mobile station. Voice communication encryptions are handled by a mobile switching center (MSC) node.
The continued development of wireless communications have added the ability for a mobile station to utilize both voice communications and packet-switched communications. Packet-switched communications are handled between a mobile station and a packet mobile switching center (PMSC) packet-switching node. By introducing packet-switched communications services within a communications system, the mobile station is connected to the PMSC through the air interface when transmitting packet data.
Since the algorithm for calculating the encryption key is secret and complex, it is not a preferred solution to implement the same algorithm on the PMSC node along with the algorithm on the MSC node. Furthermore, by implementing the algorithm on two separate nodes, synchronization problems may occur during hardware/software upgrades of the nodes. Thus, some method for enabling encryption between the mobile station and both MSC and PMSC nodes is desired.
SUMMARY OF THE INVENTION
The present invention overcomes the foregoing and other problems with a system and method for encrypting transmissions between mobile switching center and packet mobile switching center nodes and a mobile station. An encryption algorithm for generating an encryption key reside within the mobile switching center node. In response to a packet data communications request between the packet mobile switching node and the mobile station, a random number is generated by the PMSC. The random number is transmitted from the packet mobile switching center to the mobile switching center over an interface interconnecting the two nodes using a PMAP protocol. Utilizing the provided random number, the mobile switching center calculates the encryption key and the countersign from the random number and transmits the key and the countersign back to the packet mobile switching center over the same PMAP protocol interface.
At the same time, the packet mobile switching center transmits a request for the countersign to the requesting mobile station. The mobile station calculates the encryption key and the countersign utilizing the provided random number generated at the packet mobile switching center and transmits the countersign back to the packet mobile switching center node. The packet mobile switching center node compares the countersigns received from the mobile switching center and the mobile station to confirm that they match. If the provided countersigns match, transmissions between the packet mobile switching center and the mobile station are encrypted utilizing the calculated encryption key.
REFERENCES:
patent: 4182933 (1980-01-01), Rosenblum
patent: 5642401 (1997-06-01), Yahagi
patent: 6047194 (2000-04-01), Andersson
patent: WO 97/12461 (1997-04-01), None
Menezes et al., Handbook of Applied Cryptography, 1997, CRC Press, pp. 544-547.*
Standard Search Report for RS 101804 US Completed on May 7, 1999.
Hansson Rolf Elis Gustaf
Sundell Hans-Olof
Jenkens & Gilchrist P.C.
Peeso Thomas R.
Telefonaktiebolaget LM Ericsson (publ)
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