Data transmission links

• US 20030210789A1
• Filed: 01/16/2003
• Published: 11/13/2003
• Est. Priority Date: 01/17/2002
• Status: Abandoned Application

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Farnham, Timothy David, Yeun, Chan Yeob
• Application Number:
  US10/345,227
• Publication Number:
  US 20030210789A1
• Time in Patent Office: Days
• US Class Current: 380/270
• CPC Class Codes: H04L 2209/80 Wireless
• CPC Class Codes: H04L 63/12 Applying verification of the received information cryptographic mechanisms or cryptographic arrangements for data integrity or data verification H04L9/32
• CPC Class Codes: H04L 9/0844 with user authentication or key authentication, e.g. ElGamal, MTI, MQV-Menezes-Qu-Vanstone protocol or Diffie-Hellman protocols using implicitly-certified keys
• CPC Class Codes: H04L 9/3297 involving time stamps, e.g. generation of time stamps
• CPC Class Codes: H04W 12/04 Key management, e.g. using generic bootstrapping architecture [GBA]
• CPC Class Codes: H04W 12/10 Integrity
• CPC Class Codes: H04W 12/35 Protecting application or service provisioning, e.g. securing SIM application provisioning
• CPC Class Codes: H04W 12/61 Time-dependent

Abstract

This invention generally relates to secure communications links for data transmission and more particularly relates to data communications links in which asymmetric cryptographic techniques are used to establish a secure link using symmetric cryptography.

A method of establishing a secure communications link between a mobile terminal of a mobile communications system and a server, the method comprising: retrieving from storage, in the mobile terminal a prime number, p, and generator, g, for a Diffie-Hillman key exchange protocol; generating a positive integer b at the terminal; sending a message including the value of (g^bmod p) from the terminal to the server; determining a shared secret number for the terminal and the server by calculating the value of (g^ab mod p), where a is a positive integer, at both the terminal and the server, using b and a public value for the server y=g^a mod p at the terminal, and using a, b, g and p at the server; and using the shared secret number to establish said secure communications between the terminal and the server. Corresponding software is also provided.

The method facilitates fast and if desired, anonymous, download of software to a mobile communications system terminal.

Claims

1. A method of establishing a secure communications link between a mobile terminal of a mobile communications system and a server, the method comprising:

retrieving from storage, in the mobile terminal a prime number, p, and generator, g, for a Diffie-Hellman key exchange protocol;

generating a positive integer b less than p−

1 at the terminal;

sending a message including the value of (g^bmod p) from the terminal to the server;

determining a shared secret number for the terminal and the server by calculating the value of (g^ab mod p), where a is a positive integer less than p−

1, at both the terminal and the server, using b and a value y=g^a mod p for the server at the terminal, and using a, b, g and p at the server; and

using the shared secret number to establish said secure communications between the terminal and the server.

2. A method as claimed in claim 1 further comprising retrieving from storage in the mobile terminal the public value y.

3. A method as claimed in claim 1 further comprising:

encrypting the public value y at the server end of the communications link using a public key for the terminal, the public key being a key of an asymmetric cryptographic technique, to provide a first encrypted message;

sending the first encrypted message to the terminal; and

decrypting the public value y from the first encrypted message at the terminal.

4. A method as claimed in claim 3 wherein said encrypting further comprising encrypting an identifier for the server, whereby said first encrypted message includes said server identifier;

wherein said decrypting further comprises decrypting said server identifier; and

wherein the method further comprising checking said server identifier at the terminal.

5. A method as claimed in claim 3 wherein said encrypting further comprises encrypting a server-end time stamp, whereby said first encrypted message includes said server-end time stamp;

wherein said decrypting comprises decrypting said server-end time stamp for validating said secure communications link.

6. A method as claimed in claim 4 wherein said encrypting further comprises encrypting a server-end time stamp, whereby said first encrypted message includes said server-end time stamp;

wherein said decrypting comprises decrypting said server-end time stamp for validating said secure communications link.

7. A method according to claim 1 further comprising:

encrypting the value of (g^b mod p) at the terminal using a public key for the server, the public key being a key of an asymmetric cryptographic technique, to provide a second encrypted message;

sending the second encrypted message to the server; and

decrypting the value of (g^b mod p) from the second encrypted message at the server.

8. A method according to claim 7 wherein said encrypting further comprises encrypting an identifier for the terminal, whereby said second encrypted message includes said terminal identifier;

wherein said decrypting further comprises decrypting said terminal identifier; and

wherein the method further comprising checking said terminal identifier at the server.

9. A method according to claim 7 wherein said encrypting further comprises encrypting a terminal-end time stamp, whereby said second encrypted message includes said terminal-end time stamp;

wherein said decrypting further comprises decrypting said terminal-end time stamp for validating said secure communications link.

10. A method according to claim 8 wherein said encrypting further comprises encrypting a terminal-end time stamp, whereby said second encrypted message includes said terminal-end time stamp;

wherein said decrypting further comprises decrypting said terminal-end time stamp for validating said secure communications link.

11. A method according to claim 5 further comprising:

encrypting the value of (g^b mod p) at the terminal using a public key for the server, the public key being a key of an asymmetric cryptographic technique, to provide a second encrypted message;

sending the second encrypted message to the server; and

decrypting the value of (g^b mod p) from the second encrypted message at the server and wherein

said encrypting further comprises encrypting a terminal-end time stamp, whereby said second encrypted message includes said terminal-end time stamp,

said decrypting further comprises decrypting said terminal-end time stamp for validating said secure communications link, and

said second encrypted message includes said server-end time stamp.

12. A method according to claim 1 further comprising:

sending a message digitally signed by the server from the server to the terminal.

13. A method according to claim 12 wherein the digital signature provides for message recovery, and wherein the message which is digitally signed comprises at least a licence identifier.

14. A method according to claim 12 wherein the message digitally signed by the server includes data encrypted using said shared secret number.

15. A method according to claim 13 wherein the message digitally signed by the server includes data encrypted using said shared secret number.

16. A method of securely communicating data comprising establishing a secure communications link by the method of claim 1 and securely communicating data over the link.

17. A method as claimed in claim 1 wherein the message including the value of (g^b mod p) comprises a digital signature from which the value of (g^b mod p) is recoverable.

20. A data transmission link configured to implement the method of claim 1 or 18.

21. A carrier carrying computer program code for a terminal to implement the part of the method of claim 1 performed at the terminal end of the communications link.

22. A mobile terminal including the carrier of claim 21.

25. A carrier carrying computer program code for a server to implement the part of the method claim 1 performed at the server end of the communications link.

26. A server including the carrier of claim 25.

18. A method of establishing a secure communications link between a server of a mobile communications system and a mobile terminal, the method comprising:

retrieving from storage, in the server a prime number, p, and generator, g, for a Diffie-Hellman key exchange protocol;

generating a positive integer b less than p−

1 at the server;

sending a message including the value of (g^bmod p) from the server to the terminal;

determining a shared secret number for the server and the terminal by calculating the value of (g^ab mod p), where a is a positive integer less than p−

1, at both the server and the terminal, using b and a value y=g^a mod p for the terminal at the server, and using a, b, g and p at the server; and

using the shared secret number to establish said secure communications between the server and the terminal.

19. A method as claimed in claim 18 wherein the message including the value of (g^b mod p) comprises a digital signature from which the value of (g^b mod p) is recoverable.

23. A carrier carrying computer program code for a terminal to implement the part of the method of claim 18 performed at the terminal end of the communications link.

24. A mobile terminal including the carrier of claim 23.

27. A carrier carrying computer program code for a server to implement the part of the method claim 18 performed at the server end of the communications link.

28. A server including the carrier of claim 27.