Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W12/00—Security arrangements; Authentication; Protecting privacy or anonymity
  • H04W12/04—Key management, e.g. using generic bootstrapping architecture [GBA]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W12/00—Security arrangements; Authentication; Protecting privacy or anonymity
  • H04W12/03—Protecting confidentiality, e.g. by encryption
  • H04W12/033—Protecting confidentiality, e.g. by encryption of the user plane, e.g. user's traffic
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L63/00—Network architectures or network communication protocols for network security
  • H04L63/06—Network architectures or network communication protocols for network security for supporting key management in a packet data network
  • H04L63/062—Network architectures or network communication protocols for network security for supporting key management in a packet data network for key distribution, e.g. centrally by trusted party

Definitions

• the present invention relates to a method as defined in the preamble of claim 1 for computing the key to an encryption algorithm used to encrypt messages transmitted over a telecommunication network and for generating the seed number needed for the computation of the encryption key by making use of the subscriber identity module of a mobile station.
• the invention relates to a system as defined in the preamble of claim 7 for computing the key to an encryption algorithm used to encrypt messages transmitted over a telecommunication network and for generating the seed number needed for the computation of the encryption key by making use of the subscriber identity module of a mobi- le station.
• SIM cards Subscriber Identity Module
• the encryption algorithm implementing the encryption needs an encryption key.
• a method is known in which a separate algorithm for computing the encryption key is implemented in the subscriber identity module of a mobile station.
• the encryption key is stored on the subscriber identity module in conjunction with manufacture.
• the encryption key is stored on the subscriber identity module when the latter is taken into use.
• a problem with the prior-art methods is that managing the seed number needed for the computation of the encryption key and/or managing the encryption key is difficult and, e.g.
• a further problem is that an encryption key permanently stored on the subscriber identity module is not as secure as an encryption key having a variable value.
• the object of the present invention is to disclose a new type of method that eliminates the problems described above.
• a further object of the invention is to disclose a system that can be used to implement said method.
• a specific object of the present invention is to disclose a method and a system that allow flexible and safe management of seed numbers and encryption keys.
• the encryption key. required by the encryption algorithm used for the encryption of communication is computed from a certain seed number by making use of the subscriber identity module of the mobile station.
• the mobile station When the mobile station is activated, its subscriber identity module performs an authentication procedure with the mobile communication network. This is done by using an operator- specific authentication algorithm and a seed number consisting of a random number RAND generated by the mobile communication network.
• the same authentication algorithm can be used to compute an encryption key.
• the seed number is a number computed on the basis of a ran- dom number RAND generated by the authentication centre AC of the mobile communication network.
• an application in the subscriber identity module computes the encryption key and stores it in the subscriber identity module. This encryption key is used when messages are to be encrypted and/or decrypted.
• the present invention has the advantage that it makes the management of seed numbers and encryption keys considerably easier and simpler than before. As the seed numbers and encryption keys are calculated in the subscriber identity module when necessary, they need not be transmitted or set. A further advantage is that no separate equipment is needed for the management of seed numbers and encryption keys, which means that cost savings are achieved.
• the invention also increases security. In the met- hod of the invention, the encryption key changes continuously and it is not transmitted anywhere, thus considerably reducing the chance of its getting into the hands of outsiders.
• a seed number is calculated from a random number RAND generated by the authentication centre, producing a seed number such as RA D+1.
• the encryption key is computed by using an A3 algorithm, which is an operator-specific authentication algorithm.
• one or more encryption keys are used.
• each application requiring encryption has its own encryption key, thus increasing security.
• the encryption key is computed by using one or more successive algorithms so that the result of the preceding algorithm is used as the seed number for the next algorithm. This provides the advantage that the seed number for the new algorithm is changed, which leads to increased security.
• a certain portion of the random number range used by the mobile communication network is reserved for the calculation of seed numbers.
• the system of the invention for computing the key to an encryption algorithm used to encrypt messages transmitted over a telecommunication network and for generating the seed number needed for the computation of the encryption key by making use of the subscriber identity module of a mobile station comprises an encryption device and means for the transmission of encrypted messages.
• the encryption device comprises a me- ans for computing an encryption key from a seed number.
• the means used to transmit encrypted messages comprise a mobile station and an encryption server.
• an encryption device is implemented both in the subscriber identity module and in the authentication centre.
• the encryption device comprises a device for storing the encryption key.
• the mobile station is GSM compatible.
• Fig. 2 presents an example representing the hardware configuration of the system of the invention.
• Fig. la illustrates a method in which the mobile communication network generates a random number RAND and sends it to the subscriber identity module 9. Based on this random number, a seed number RAND+1 is calculated.
• This seed number 1 and the identification key Kj . 2 are input as starting values to an A3 algorithm 3.
• the identification key K 2 is a user-specific secret parameter, which has been stored in the subscriber identity module 9 and in the authentication centre 10.
• the A3 algorithm 3 is the same operator-specific algorithm that is used when the subscriber identity module 9 carries out an authentication procedure with the authentication centre 10 of the mobile communication network upon activation of the mobile station 8.
• a feature characteristic of the A3 algorithm 3 is that com- puting the encryption key 4 from the seed number 1 and the identification key K ⁇ 2 is easy, but determining the identification key 2 on the basis of the seed number 1 and the encryption key 4 is extremely difficult.
• the encryption key 4 is the result produced by the algorithm 3. This encryption key 4 is used when messages are to be encrypted and/or decrypted.
• Fig. lb illustrates a variation of the method of the previous example.
• the random number range is 0 - 10000. It is divided into two halves so that the random number RAND values 0 - 4999 are reserved for the computation of seed numbers 5.
• the mobile communication network generates a random number RAND and sends it to the subscriber identity module 9. Based on the random number, a seed number RAND+5000 is calculated.
• the seed number 5 and the identification key K L 2 are input as starting values to the A3 algorithm 3, which produces a new seed number 6 as a result.
• the new seed number 6 thus computed and the identification key Kj . 2 are given as starting values to a new algorithm 7.
• the result obtained is used as the final encryption key .
• the advantage provided by this alternative is that the seed number ⁇ for the new algorithm 7 is automatically changed.
• Fig. 2 illustrates a system in which encrypted short messages are transmitted between a GSM telephone 8 and an encryption server 12 in a GSM network.
• An encryption device 11 has been implemented both in the subscriber identity module 9 of the mobile station 8 and in the authentication 10 of the GSM network.
• the encryption device 11 comprises a SIM Application Toolkit, an application that computes the encryption key 4.
• the encryption device 11 stores the compu- ted encryption key 4 for use.
• the encryption device 11 computes an encryption key 4 on the basis of a seed number 1 and a user-specific identification key Ki 2 both on the SIM card 9 and in the authentica- tion centre 10.
• an encryption algorithm such as an RSA or 3DES algorithm, implemented both on the SIM card and in the authentication server 12, encrypts/decrypts the message.
• the key 4 is stored for the next time it is needed, or a new value for the key is computed each time.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Security & Cryptography (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=8549914

Family Applications (1)

Country Status (7)

Families Citing this family (14)

Family Cites Families (6)

• 1997
  • 1997-11-11 FI FI974198A patent/FI105253B/fi active
• 1998
  • 1998-11-11 EP EP98958929A patent/EP1025739A2/de not_active Withdrawn
  • 1998-11-11 JP JP2000519968A patent/JP2001523064A/ja not_active Withdrawn
  • 1998-11-11 CA CA002309666A patent/CA2309666A1/en not_active Abandoned
  • 1998-11-11 WO PCT/FI1998/000879 patent/WO1999025086A2/en not_active Application Discontinuation
  • 1998-11-11 NZ NZ504378A patent/NZ504378A/en unknown
  • 1998-11-11 AU AU14892/99A patent/AU1489299A/en not_active Abandoned

Non-Patent Citations (1)

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