Method and apparatus for performing a key update using update key
View Patent ↗A system for updating a communications key(s) performs an authentication(s) of the unit and/or of the communications system using an update key. By using the update key to perform the authentication(s), the key update system can reduce communications between a home communications system and a visiting communications system by sending the update key to the visiting communications system while maintaining the communications key at the home communication system. For example, in performing a key update, the home communications system generates a communications key, such as a new authentication key SSD-A-NEW, using a sequence RANDSSD generated at the home communications system and a secret key A-KEY maintained at the home communications system and at the unit. The home communications system generates the update key SSD-KEY also using the sequence RANDSSD and the secret key A-KEY. The home communications system sends the update key SSD-KEY and the sequence RANDSSD to the visiting communications system, and the visiting communications system sends the sequence RANDSSD to the unit. The unit generates the new communications key, such as the new authentication key SSD-A-NEW, and the update key SSD-KEY in the same manner as the home communications system. Because the visiting communications system has the update key SSD-KEY, the visiting authentication system can generate the signature value(s) AUTHSSD and/or AUTHBS using the update key at the visiting communications system to authenticate the unit and/or the communications system.
1. A method of updating a communications key maintained in a unit for communicating with a communications system, said method comprising:
generating a new communications key using a secret value stored in said unit;
generating an update key using said secret value stored in said unit;
generating a signature value using said update key;
comparing said signature value with a signature value received from a visiting communications system of said communications system which was generated by said visiting communications system using an update key derived by a home communications system of said communications system; and
updating said communications key with said new communications key depending on the results of said comparison.
2. The method of claim 1 comprising:
receiving an update sequence; and
generating said new communications key using said secret value stored in said unit and said update sequence.
3. The method of claim 2 further comprises:
generating a challenge sequence;
sending said challenge sequence to said visiting communications system;
generating said signature value using said challenge sequence and said update key;
receiving said signature string generated by said visiting communications system using said challenge sequence and said update key; and
comparing said signature value with said signature value generated by said visiting communications system.
4. The method of claim 3 comprises:
generating a second signature value using said update sequence a nd said up date key; and
sending said second signature value to said visiting communications system for comparison with a second signature value generated by said visiting communications system using said sequence and said update key generated at said communications system.
5. The method of claim 3 wherein said generating said signature value includes:
developing a signature string comprising at least portions of said update sequence, said challenge sequence and said update key; and
generating said signature value from at least said signature string.
6. The method of claim 4 wherein said generating said signature value includes:
developing a second signature string comprising at least portions of said update sequence, said challenge sequence and said update key; and
generating said second signature value from at least said second signature string.
7. A method of updating a communications key maintained in a unit and in a communications system, said method comprising:
receiving by a visiting communications system from a home communications system an update sequence and an update key derived by said home communications system using a secret value associated with said unit and stored in said home communications system;
sending by said visiting communications system to said unit said update sequence for said unit to generate a new communications key using a secret value in said unit;
generating a signature value at said visiting communications system using said update key derived by said home communications system;
sending by said visiting communications system to said unit said signature value generated at said visiting communications system for said unit to compare with a signature value generated at said unit using an update key generated by said unit using said secret value stored in said unit; and
receiving an update confirmation depending on the results of said comparison.
8. The method of claim 7 wherein said generating a signature value including:
receiving a challenge sequence from said unit; and
generating said signature value using said challenge sequence and said update key.
9. The method of claim 8 including:
generating a second signature value using said update sequence and said update key;
receiving a second signature value generated at said unit using said update sequence and said update key at said unit; and
comparing with said second signature value with said second signature value generated by said unit.
10. The method of claim 9 wherein said generating a signature value including:
developing a signature string comprising at least portions of said update sequence, said challenge sequence and said update key; and
generating said signature value from at least said signature string.
11. The method of claim 9 wherein said generating a second signature value including:
developing a second signature string comprising at least portions of said update sequence, said challenge sequence and said update key; and
generating said second signature value from at least said second signature string.
12. A method of updating a communications key maintained in a unit and in a communications system, said method comprising:
generating an update sequence;
generating by a home communications system a new communications key using a secret value stored in said home communications system and associated with said unit;
generating by said home communications system an update key using said secret value;
sending said update key to a visiting communications system for said visiting communications system to generate a signature value, using said update key derived by said home communications system, which is sent to said unit for comparison to a signature value generated at said unit using an update key generated at said unit using a secret value stored in said unit;
updating said communications key with said new communications key depending on the results of said comparison.
13. A method of updating a communications key maintained in a unit and in a home communications system, said method comprising:
receiving an update sequence from said home communications system for said unit to generate a new communications key using a secret value in said unit;
receiving an update key from said home communications system and generated at said home communications system using a secret value associated with said unit at said home communications system;
generating by a visiting communications system a signature value using said update key derived by said home communications system;
performing an authentication with said unit using said signature value; and
sending to said home communications system the results of said authentication.
14. A communications key update system for updating a communications key maintained in a unit for communicating with a communications system, said system configured to generate a new communications key using a secret value stored in said unit, generate an update key using said secret value stored in said unit, generate a signature value using said update key, compare said signature value with a signature value received from a visiting communications system of said communications system which was generated by said visiting communications system using an update key derived by a home communications system of said communications system, and update said communications key with said new communications key depending on the results of said comparison.
15. A key update system for updating a communications key maintained in a unit and in a communications system, said system configured to receive from a home communications system an update sequence and an update key derived by said home communications system using a secret value associated with said unit and stored in said home communications system, to send to said unit said update sequence for said unit to generate a new communications key using a secret value in said unit, to generate a signature value at said visiting communications system using said update key derived by said home communications system, to send to said unit said signature value for said unit to compare with a signature value generated at said unit using an update key generated by said unit using said secret value stored in said unit, and to receive an update confirmation depending on the results of said comparison.
16. A key update system for updating a communication key maintained in a unit and in a communications system, said system configured to generate an update sequence, to generate a new communications key using a secret value stored in said system and associated with said unit, to generate by a home communications system an update key using said secret value, to send said update key to a visiting communications system for said visiting communications system to generate a signature value, using said update key derived by said home communications system, which is sent to said unit for comparison to a signature value generated at said unit using an update key generated at said unit using a secret value stored in said unit, and to update said communications key with said new communications key depending on the results of said comparison.