Cryptography – Particular algorithmic function encoding – Nbs/des algorithm
Patent
1995-03-30
1996-09-17
Gregory, Bernarr E.
Cryptography
Particular algorithmic function encoding
Nbs/des algorithm
380 4, 380 9, 380 25, 380 49, 380 50, 235380, H04L 900, H04L 932
Patent
active
055576796
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for personalization of an active subscriber card, a so-called Subscriber Identity Module (SIM) card, for use in a mobile telephone system, comprising a central computer, the unique identity of the card, so-called International Mobile Subscriber Identification (IMSI), and the unique authentication key of the card, Ki, being stored in the card from the central computer. The invention is especially applicable to a mobile telephone system such as the Global Systems for Mobile Communications (GSM) and will be described in more detail with reference thereto, although it is obvious that the invention is also applicable to other mobile telephone systems of a similar type.
TECHNICAL BACKGROUND
In mobile telephone systems, in which the mobile units are controlled by active cards assigned to the subscribers, the personalization of the respective card constitutes an essential procedure which is safeguarded by rigorous security measures and which includes activating the card and loading it with IMSI and Ki, and preferably also a so-called PUK code (Personal Unblocking Key). It is essential that this loading be effected in a safe manner to prevent unauthorised people from having access thereto.
In view hereof, the personalization procedure is carried out in a central personalization place or a customer service place adjacent the central computer, where it is possible to meet the high demands on security.
OBJECT OF THE INVENTION
The object of the present invention is to provide a method making it possible, still in a safe manner, to effect the personalization procedure in places other than the above-mentioned central place, whereby a number of advantages can be gained.
SUMMARY OF THE INVENTION
The above-mentioned object is achieved by a method which according to the invention has the features stated in the appended claims.
According to the invention, the storage procedure should thus be carried out when the card is in a personalization place remotely connected to the central computer via a data communication network, especially a retail place, the card being inserted in a reader associated with data terminal equipment connected to the data communication network, IMSI and Ki and preferably also PUK being transferred in line-encrypted form from the central computer to the data terminal equipment where line decryption is performed, and the result of the line decryption being transferred to the SIM card in a manner to prevent unauthorised listening-in.
A distributed personalization of this type makes it possible to divide up IMSI number series geographically, which is a major advantage in that the network signalling is simplified or reduced, and also in that the service level toward a new subscriber can be kept very high. In fact, the personalization can be effected directly and without any waiting time conditioned by the dispatch of cards, code envelopes, etc., from a central place. The direct communication with the central computer also makes it possible to provide for different special services in a rapid and simple manner.
The transfer of the result of the line decryption to the SIM card in a safe manner can be carried out in different ways.
According to a first conceivable alternative, the line decryption and the result transfer to the SIM card take place in a physically sealed space, into which any attempt of unauthorised intrusion means that relevant information is erased and that the process is interrupted and cannot be continued without special security measures being taken. Mechanical and electronic protection of this kind can be achieved by means of a special safety box, in which the circuitry concerned is enclosed during the personalization procedure.
According to a second conceivable alternative, the result of the line decryption is transferred to the SIM card in encrypted form, at least in respect of Ki. This is preferably done by encrypting Ki and preferably also PUK and optionally IMSI an extra time in the central computer before the line-enc
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Almgren Bjorn
Julin Tomas
Sandberg Leif
Comvik GSM AB
Gregory Bernarr E.
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