Method and system for providing secure key distribution in a communication system

• US 5,729,608 A
• Filed: 01/24/1996
• Issued: 03/17/1998
• Est. Priority Date: 07/27/1993
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Tsudik, Gene, Janson, Philippe
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US08/591,638
• Time in Patent Office: 783 Days
• Field of Search: 380/21, 380/28, 380/30, 380/25
• US Class Current: 713/171
• CPC Class Codes: H04L 9/0827 involving distinctive intermediate devices or communication paths network architectures or network communication protocols using different networks H04L63/18
• CPC Class Codes: H04L 9/0833 involving conference or group key network architectures or network communication protocols for key management in group communication in a packet data network H04L63/065
• CPC Class Codes: H04L 9/0897 involving additional devices, e.g. trusted platform module [TPM], smartcard or USB
• CPC Class Codes: H04L 9/321 involving a third party or a trusted authority

Abstract

A method and system for providing secure authenticated cryptographic key distribution in a communication system having properties very similar to a Two-Party Authentication Protocol. A new group key is distributed by a server to a selected group of users in the system. A braided structure of the messages, sent by the server to each user, allows authentication and, at the same time, secure and secret key distribution. Moreover, the braided structure makes it possible to construct minimal-length protocol messages.

Claims

1. A method for providing secure, authenticated distribution in a communication system of a key to be used by a group of selected users, the key being distributed from a server to a sub-group consisting of the users of said group other than said server, each user of said sub-group sharing a secret user key with said server, said method comprising the steps of:

transmitting (501,511) the user'"'"'s identification (A), a user'"'"'s nonce (N_as) and an identification (B) of a user of said sub-group other than said transmitting user from each user of said sub-group to said server through an available path of said system;

generating (502) a new, common group key (K_ab) for all users of said group by said server;

computing (503,512) the value of a first function for each user of said sub-group by said server, said first function depending upon at least said user'"'"'s key (K_as), said user'"'"'s nonce (N_as), said group key (K_ab) and the identification (B) of the user of said group other than said user;

computing (504,513) the value of a second function for each user of said sub-group by said server, said second function depending upon at least said user'"'"'s key (K_as), the value of said user'"'"'s first function and said group key (K_ab);

transmitting (505,514) the values of said user'"'"'s first and second functions from said server to each user of said sub-group through an available path of said system;

extracting (506,515) said group key, by each user of said sub-group, from the value of said user'"'"'s second function, employing said user'"'"'s key and the value of said user'"'"'s first function; and

re-computing (507,516) the value of said user'"'"'s first function by each user of said sub-group and considering authenticated said extracted group key (K_ab) if said re-computed value is equal to the value of said user'"'"'s first function received by said server.

2. The method according to claim 1, further comprising the steps of:

computing (508,517) the value of a third function by each user of said sub-group, said user'"'"'s third function depending upon at least said user'"'"'s key (K_as), said user'"'"'s nonce (N_as) and said group key (K_ab);

transmitting (509,518) the value of said user'"'"'s third function from each user of said sub-group to said server through an available path of said system; and

re-computing (510,519) the value of said user'"'"'s third function for each user of said sub-group by said server and authenticating each user of said sub-group if said re-computed value if equal to the value of said user'"'"'s third function received by said user.

3. The method according to claims 1 or 2, further comprising the step of:

each user of said sub-group authenticating (520 to

     526) itself to any other user of said sub-group by encrypting and exchanging information with said group key (K_ab) between said users.

4. The method according to claims 1 or 2, wherein said first, second and third functions are encryption functions under said user'"'"'s key (K_as).

5. The method according to claims 1 or 2, wherein said second function is an encryption function under said user'"'"'s key (K_as) of at least said user'"'"'s first function, exclusively OR-ed with said group key (K_ab).

6. The method according to claim 5, wherein said group key (K_ab) is extracted by each user of said sub-group by re-computing the value of said user'"'"'s encryption function and XOR-ing said result with the value of said user'"'"'s second function.

7. The method according to claims 1 or 2, further characterized in that:

the information to be transmitted from each user of said sub-group to the server is collected by one of the users of the system and then transmitted from said one user to said server.

8. The method according to claims 1 or 2, further characterized in that:

the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

11. The method according to claim 3, wherein said first, second and third functions are encryption functions under said user'"'"'s key (K_as).

12. The method according to claim 3, wherein said second function is an encryption function under said user'"'"'s key (K_as) of at least said user'"'"'s first function, exclusively OR-ed with said group key (K_ab).

13. The method according to claim 4, wherein said second function is an encryption function under said user'"'"'s key (K_as) of at least said user'"'"'s first function, exclusively OR-ed with said group key (K_ab).

14. The method according to claim 3, further characterized in that:

the information to be transmitted from each user of said sub-group to the server is collected by one of the users of the system and then transmitted from said one user to said server.

15. The method according to claim 4, further characterized in that:

the information to be transmitted from each user of said sub-group to the server is collected by one of the users of the system and then transmitted from said one user to said server.

16. The method according to claim 5, further characterized in that:

the information to be transmitted from each user of said sub-group to the server is collected by one of the users of the system and then transmitted from said one user to said server.

17. The method according to claim 6, further characterized in that:

the information to be transmitted from each user of said sub-group to the server is collected by one of the users of the system and then transmitted from said one user to said server.

18. The method according to claim 3, further characterized in that:

the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

19. The method according to claim 4, further characterized in that:

the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

20. The method according to claim 5, further characterized in that:

the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

21. The method according to claim 6, further characterized in that:

the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

22. The method according to claim 7, further characterized in that:

the information to be transmitted over the system is identified by a tag identifying the addressed user or server.

9. A communication system (100) for providing secure, authenticated distribution of a key to be used by a group of selected users (101,102,103,109), the key being distributed from a server (109) to a sub-group of users (101,102,103) consisting of the users of said group other than said server, each user of said sub-group sharing a corresponding secret user key with said server, said system comprising:

means for transmitting (501,511) the user'"'"'s identification, a user'"'"'s nonce and an identification of a user of said sub-group other than said user from each user of said sub-group to said server through an available path of said system;

means for generating (502) a new, common group key for all users of said group by said server;

means for computing (503,512) the value of a first function for each user of said sub-group by said server, said first function depending upon at least said user'"'"'s key, said user'"'"'s nonce, said group key and the identification of the user of said group other than said user;

means for computing (504,513) the value of a second function for each user of said sub-group by said server, said second function depending upon at least said user'"'"'s key, the value of said user'"'"'s first function and said group key;

means for transmitting (505,514) the values of said user'"'"'s first and second functions from said server to each user of said sub-group through an available path of said system;

means for extracting (506,515) said group key, by each user of said sub-group, from the value of said user'"'"'s second function, employing said user'"'"'s key and the value of said user'"'"'s first function; and

means for re-computing (507,516) the value of said user'"'"'s first function by each user of said sub-group and considering authenticated said extracted group key if said re-computed value is equal to the value of said user'"'"'s first function received by said server.

10. The communication system according to claim 9, further comprising:

means for computing (508,517) the value of a third function by each user of said sub-group, said user'"'"'s third function depending upon at least said user'"'"'s key, said user'"'"'s nonce and said group key;

means for transmitting (509,518) the value of said user'"'"'s third function from each user of said sub-group to said server through an available path of said system; and

means for re-computing (510,519) the value of said user'"'"'s third function for each user of said sub-group by said server and authenticating each user of said sub-group if said re-computed value is equal to the value of said user'"'"'s third function received by said user.