Method and apparatus for validating data packets in a paging system

• US 5,768,526 A
• Filed: 03/08/1996
• Issued: 06/16/1998
• Est. Priority Date: 03/08/1996
• Status: Expired due to Term

• Current Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Original Assignee: Glenayre Electronics Incorporated (EDCI Holdings Incorporated)
• Inventors: Fawcett, Glenn S.
• Primary Examiner(s): Rinehart, Mark H.
• Application Number:
  US08/612,748
• Time in Patent Office: 830 Days
• Field of Search: 395/200.18, 395/200.5, 395/200.12, 395/200.06, 395/187.01, 395/222.5, 395/200.36, 395/200.55, 395/200.59, 395/200.68, 395/421.06 , 395/200.76, 380/49, 370/338, 370/313, 364/949.71, 364/260.81, 340/825.44, 340/825.34
• US Class Current: 709/229
• CPC Class Codes: H04L 63/123 received data contents, e.g. message integrity
• CPC Class Codes: H04L 9/3239 involving non-keyed hash functions, e.g. modification detection codes [MDCs], MD5, SHA or RIPEMD
• CPC Class Codes: H04L 9/3297 involving time stamps, e.g. generation of time stamps
• CPC Class Codes: H04W 12/10 Integrity
• CPC Class Codes: H04W 12/61 Time-dependent
• CPC Class Codes: H04W 84/022 One-way selective calling networks, e.g. wide area paging

Abstract

A method of validating communications between a transmitting component and a receiving component of a paging system is disclosed. The transmitting component prepares an application protocol data unit (APDU) for transmission by selecting predetermined portions of the APDU for hashing. A hash code is output by the hash method and included in the APDU. The receiving component retrieves the same predetermined portions of the APDU for hashing. The receiving component then compares the hash code in the APDU with the hash code the receiving component calculated. If there is a match, then the APDU is accepted as authentic. If there is not a match, then the APDU is rejected.

Claims

1. A method for validating a data packet transmitted between components of a paging infrastructure system, the paging infrastructure system including at least a transmitting component and a receiving component, said data packet being an application protocol data unit (APDU) that includes a destination ID a message sequence number, a message length, and a time and date stamp, the method comprising the steps of:

(a) extracting predetermined portions of the data packet for hashing by the transmitting component;

(b) performing a hash method on said predetermined portions of the data packet to generate a transmit hash code, wherein said predetermined portions include said destination ID, said message sequence number, said message length, and said time and date stamp;

(c) inserting said transmit hash code into the data packet;

(d) transmitting the data packet to said receiving component;

(e) extracting said predetermined portions of the data packet for hashing by the receiving component;

(f) performing said hash method on said predetermined portions of the data packet to generate a receive hash code;

(g) comparing said receive hash code with said transmit hash code; and

(h) accepting the data packet if there is a match between said receive hash code and said transmit hash code.

2. The method of claim 1 wherein said receiving component has a receive component destination ID and further including the step of examining the destination ID of said APDU and accepting said APDU only if said the destination ID of said APDU matches said receive component destination ID.

3. The method of claim 1 further including the step of examining said message length of said APDU and accepting said APDU only if said message length of said APDU matches the actual length of said APDU.

4. The method of claim 1 further including the step of having the receiving component maintain a record of a valid range of said message sequence numbers of APDUs previously received within a predetermined amount of time and discarding any newly received APDU that has a message sequence number outside of said valid range.

5. The method of claim 1 wherein said receiving component maintains a clock and further including the step of examining the time and date stamp of said APDU and accepting said APDU only if said the time and date stamp of said APDU is within a predetermined time from the time and date as indicated by said clock.

6. The method of claim 1 wherein said step of performing said hash method by said transmitting component is done on said predetermined portions and a password and said step of performing said hash method by said receiving component is done on said predetermined portions and said password.

7. The method of claim 6 wherein said predetermined portions include said destination ID, said message sequence number, said message length, and said time and date stamp.

8. The method of claim 6 wherein said receiving component has a receive component destination ID and further including the step of examining the destination ID of said APDU and accepting said APDU only if said the destination ID of said APDU matches said receive component destination ID.

9. The method of claim 6 further including the step of examining said message length of said APDU and accepting said APDU only if said message length of said APDU matches the actual length of said APDU.

10. The method of claim 6 further including the step of having the receiving component maintain a record of a valid range of said message sequence numbers of APDUs previously received within a predetermined amount of time and discarding any newly received APDU that has a message sequence number outside of said valid range.

11. The method of claim 6 wherein said receiving component maintains a clock and further including the step of examining the time and date stamp of said APDU and accepting said APDU only if said the time and date stamp of said APDU is within a predetermined time from the time and date as indicated by said clock.

12. A method for securely transmitting a data packet between components of a paging infrastructure system, the paging infrastructure system including at least a transmitting component and a receiving component, the method comprising the steps of:

(a) extracting predetermined portions of the data packet for hashing by the transmitting component, said predetermined portions comprising input words of thirty-two bits;

(b) performing a hash method on said predetermined portions of the data packet to generate a transmit hash code, said hash method comprising the steps of;

(i) expanding said input words into an expanded set of words, each of said words of said expanded set being a combination of said input words using exclusive-or operations;

(ii) initializing a set of storage words;

(iii) modifying said set of storage words by evenly dividing said expanded set of words into four groups of words to be processed sequentially combining all said storage words with all words of one group using rotations, additions, and subtractions in combination with a different non-linear Boolean operation for each group, and storing the results into said storage words and repeating for each group;

(iv) combining said set of storage words into said transmit hash code using a weighted sum;

(c) inserting said transmit hash code into the data packet;

(d) transmitting the data packet to said receiving component;

(e) extracting said predetermined portions of the data packet for hashing by the receiving component;

(f) performing said hash method on said predetermined portions of the data packet to generate a receive hash code;

(g) comparing said receive hash code with said transmit hash code; and

(h) accepting the data packet if there is a match between said receive hash code and said transmit hash code.

13. The method of claim 12 wherein said input words are twelve 32-bit words, said expanded set is seventy-two 32-bit words, and said set of storage words includes five 32-bit words.