United States Patent [w]
US006070246A [ii] Patent Number:  Date of Patent:
 METHOD AND SYSTEM FOR SECURE CABLE MODEM INITIALIZATION
 Inventor: Nurettin B. Beser, Evanston, 111.
 Assignee: 3Com Corporation, Santa Clara, Calif.
 Appl. No.: 09/018,756  Filed: Feb. 4, 1998
 Int. CI. G06F 11/00
 U.S. CI 713/201
 Field of Search 713/200, 201,
713/1; 707/203; 709/219, 217, 220; 380/23,
 References Cited
U.S. PATENT DOCUMENTS
5,014,234 5/1991 Edwards, Jr 364/900
5,138,712 8/1992 Corbin 395/700
5,623,601 4/1997 Vu 395/187.01
5,799,086 8/1998 Sudia 380/23
5,958,007 9/1999 Lee et al 709/219
Primary Examiner—Dennis M. Butler
Assistant Examiner—Omar A. Omar
Attorney, Agent, or Firm—McDonnell Boehnen Hulbert &
Berghoff; Stephen Lesavich
A method and system for secure cable modem initialization in a data-over-cable system is provided using a secure protocol server. The method includes sending a unique identifier, such an Internet Protocol ("IP") address and a selected time-value, such as an approximate message send time-value, in a configuration file from a protocol server such as a Trivial File Protocol server ("TFTP"). A message integrity value is calculated using the unique identifier, the selected time-value and one or more configuration parameters in a pre-determined order with a cryptographic hashing function. The message integrity value is added to the configuration file. A cable modem receives the configuration file from the TFTP server and uses the message integrity value to authenticate the configuration file and determine if the configuration file was sent within a pre-determined period of time (e.g., 5 seconds) from the TFTP server. If not, the configuration is discarded by the cable modem. The unique identifier and selected time-value uniquely identify the configuration file for the cable modem and help prevent a rouge user from intercepting a valid cable modem configuration file and using it at a later time to initialize a rouge cable modem. The method and system provide improved security for initializing cable modems in a data-over-cable system.
22 Claims, 28 Drawing Sheets