Cryptography – Cellular telephone cryptographic authentication – Visiting center
Reexamination Certificate
1997-12-10
2004-02-10
Barrón, Gilberto (Department: 2132)
Cryptography
Cellular telephone cryptographic authentication
Visiting center
C455S410000, C455S433000
Reexamination Certificate
active
06690798
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to satellite communication systems and, in particular, to utilizing key transforms to discriminate between beams in a multiple-beam satellite communication system.
2. Description of Related Art and Objects of the Invention
Mobile wireless communication is becoming increasingly important for safety, convenience, and efficiency. One prominent mobile communication option is cellular communication. Cellular phones, for instance, can be found in cars, briefcases, purses, and even pockets. Cellular phones, like most mobile communication options, rely on the transmission of electromagnetic radiation from one point to another.
In general, a cellular mobile communications system is composed of many cells, each with a base station antenna for receiving transmissions. From the base station, the cellular system has interfaces for routing a call through or to the land-based, or terrestrial, telephone network, often referred to as the public switched telephone network (PSTN). The base stations form one half of the cellular system. Cell phones, called mobile stations, mobile terminals, or merely terminals, form the second half of the cellular system. In short then, electromagnetic radiation transmissions between terminals and base stations are an essential component of cellular systems, and such transmissions must be optimized by the cellular system to maximize cellular phone service, quality, and security.
Security becomes even more difficult to ensure when using satellites in a mobile communications system because the electromagnetic beams transmitted from the satellites can overlap countries and even continents. Therefore, a person on one continent can eavesdrop on another person's conversation on an entirely different continent. Nevertheless, satellite-based communication systems are desirable because they enable global coverage without necessitating closely-spaced cellular base stations.
Throughout the following, the terms cellular mobile telephone, cellular phone, cellular telephone, mobile telephone, phone, radiotelephone terminal, cellular terminal, mobile terminal, and “terminal” may be used equivalently to refer to a wireless communications device capable of wirelessly transmitting and receiving data. Also, the terms radiotelephone network, cellular system, and cellular network are used equivalently to refer to a wireless communications system which provides wireless data connections between two or more terminals or between two or more terminals and other equipment.
Cellular mobile telephones and other such radio communications devices are usually designed to meet the requirements of a limited number of standards in common use in the world. Many countries choose the same standard; for example the pan-European Global System for Mobile Communications (GSM) is used by 14 European countries, Australia, and some Middle Eastern countries. The U.S. digital cellular standard, IS-54B Cellular System Dual-Mode Mobile Station-Base Station Compatibility Standard (available from the Telecommunications Industry Association, 2001 Pennsylvania Avenue, N.W., Washington D.C., 20006) (IS-54B) is used, for example, in the USA, Mexico, Canada, and South America. As a result of their being only a handful of mobile communication system standards, as well as economies of scale, mobile telephones are produced in enormous volume and generally adapted so that the design is the same for many markets.
The current invention belongs to the field of anti-fraud and privacy systems for public or private wireless communications systems, such as digital cellular telephone systems. Such systems may use authentication procedures for verifying the identity of a mobile phone attempting to access the network or to verify the network to the phone, as well as scrambling to prevent traffic broadcast to one mobile accidentally or deliberately being received by another.
A problem that has arisen before is that mobile telephone numbers are re-used in other countries and therefore not guaranteed to be unique in the whole world. Thus, an IS-54B telephone from a Far Eastern country brought to the United States by a traveler may have the same telephone number (mobile identification number, or MIN) as a “native” American phone, and can sometimes access the network in an unforeseen manner, including fraudulently. It is an object of anti-fraud systems to prevent such unauthorized access.
Anti-fraud systems make use of a secret number like a PIN code embedded into every phone. The number stored in the phone is also stored in the telephone exchange belonging to the operator with which the user has a subscription. A phone attempting to access a network is “challenged” with a random number which it is invited to combine with the secret PIN code in a defined way and to return a result. The network meanwhile contacts the phone's home exchange with the random number and invites it to do likewise. If the result from the phone matches that from the home exchange, the phone is admitted to the network, and the network is fairly certain that its bill for services can be sent to the phone's home operator and that it will be honored.
While it may not be too difficult to ensure that unique PIN codes are issued to all phones registered with a particular operator, it is not so obvious how to coordinate PIN code issuance between operators to guarantee uniqueness, without compromising security by allowing too many organizations to have access to secret information. It is not very likely that all the coordination required could be achieved between continents. Therefore, the invention provides a means of discriminating the security information between different networks such that uniqueness of the information is not a necessity.
U.S. Pat. No. 5,091,942, granted to applicant, which is hereby incorporated by reference in its entirety herein, discloses a bilateral authentication procedure that verifies a mobile phone to the network as well as the network to the phone. The inventive bilateral authentication system also produces as a byproduct a temporary variable to be used for scrambling traffic. U.S. Pat. Number 5,060,266, also granted to applicant, which is also hereby incorporated by reference in its entirety herein, describes a type of scrambling system suitable for such purposes. Furthermore, a suitable algorithm is described in U.S. patent application Ser. No. 07/556,358 (Dent, filed Jul. 20, 1990), which is also hereby incorporated by reference in its entirety herein.
The referenced prior art discloses use of a 64-bit temporary key, which is produced during the authentication procedure, to generate with the aid of a speech frame or time division multiple access (TDMA) transmission frame counter, a block of keystream bits for every frame which may be exclusive-ORed to traffic data to prevent it being received by a radio not in possession of the same 64 bits. The known prior art does not provide a means to ensure that radios of the same design, delivered to perhaps different continents and accidentally in possession of the same 64-bit key, cannot receive or transmit the same signal.
It is an objective of the invention to provide a means whereby portable communications devices such as cellular phones can be delivered all over the world with the same design without compromising the security of anti-fraud and privacy features in any one country or continent. This is particularly desirable in connection with global satellite communications systems which may be constructed using multiple-beam satellite systems as described, for example, jointly by U.S. Pat. Nos. 5,594,941, 5,555,271, 5,619,503, 5,619,210, 5,594,776, 5,535,432, and 5,610,559, and by U.S. patent applications Ser. Nos. 08/225,399 (filed Apr. 8, 1994) and 08/368,877 (filed Jan. 5, 1995) which is a continuation-in-part of 08/179,958 (filed Jan. 11, 1994). All disclosures of which are hereby incorporated by reference in their entirety herein.
A particular case of the problems referred to a
Barrón Gilberto
Ericsson Inc.
Meislahn Douglas J.
Myers Bigel & Sibley & Sajovec
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