Method for detecting the removal of a processing unit from a printed circuit board

• US 20080148415A1
• Filed: 12/19/2006
• Published: 06/19/2008
• Est. Priority Date: 12/19/2006
• Status: Active Grant

• Current Assignee: Pitney Bowes Incorporated (Böwe Systec AG)
• Original Assignee: Pitney Bowes Incorporated (Böwe Systec AG)
• Inventors: Jacobson, Gary S., Kirschner, Wesley A., Hurd, John A., Sisson, Robert W., Ryan, Frederick W.
• Granted Patent: US 8,308,819 B2
• Time in Patent Office: Days
• US Class Current: 726/35
• CPC Class Codes: G06F 21/554 involving event detection and direct action
• CPC Class Codes: G06F 21/725 operating on a secure reference time value
• CPC Class Codes: G06F 21/86 Secure or tamper-resistant housings
• CPC Class Codes: G07B 17/00314 Communication within apparatus, personal computer [PC] system, or server, e.g. between printhead and central unit in a franking machine
• CPC Class Codes: G07B 2017/00258 Electronic hardware aspects, e.g. type of circuits used
• CPC Class Codes: G07B 2017/00322 Communication between components/modules/parts, e.g. printer, printhead, keyboard, conveyor or central unit
• CPC Class Codes: G07B 2017/00411 Redundant storage, e.g. back-up of registers

Abstract

Various methods for detecting the removal of a processing unit, such as a microprocessor or a microcontroller, form a printed circuit board in a secure printing system, such as a postage metering system are provided. The methods utilize one or more of a real time clock provided internal to the processing unit, a CMOS device provided on the printed circuit board external to the processing unit, and CMOS memory internal to the processing unit to detect the removal of the processing unit and therefore an attack.

Claims

1. A method for detecting that a processing unit has been removed from a printed circuit board, comprising:

providing said processing unit on said printed circuit board, said processing unit having a real time clock internal thereto;

providing a power source on said printed circuit board separate from said processing unit;

electrically connecting said power source to said real time clock to provide power to said real time clock;

monitoring the functioning of said real time clock; and

determining that said processing unit has been removed from said printed circuit board if one or more of the following is determined;

(i) that said real time clock has stopped keeping time, (ii) that said real time clock is not enabled, or (iii) said real time clock is reporting a time that is prior to a predetermined stored time.

2. The method according to claim 1, wherein said power source is a battery.

3. The method according to claim 1, wherein said printed circuit board is included within a secure printing system.

4. A method for detecting that a processing unit has been removed from a printed circuit board, wherein said printed circuit board is included within a secure printing system and wherein said processing unit stores state information relating to one or more items printed by or to be printed by said secure printing system, the method comprising:

providing said processing unit on said printed circuit board, said processing unit having a real time clock internal thereto, said real time clock having one or more registers;

providing a power source on said printed circuit board separate from said processing unit;

electrically connecting said power source to said real time clock to provide power to said real time clock;

storing a representation of said state information in said one or more registers, wherein said one or more registers are able to store said representation only if said power is provided to said real time clock;

monitoring said one or more registers; and

determining that said processing unit has been removed from said printed circuit board if it determined that said one or more registers no longer store said representation of said state information.

5. The method according to claim 4, wherein said power source is a battery.

6. The method according to claim 4, wherein representation of said state information is a hash of said state information.

7. A method for detecting that a processing unit has been removed from a printed circuit board, wherein said printed circuit board is included within a secure printing system for printing a plurality of items, wherein each of said items has a sequence number associated therewith, and wherein said items are printed in order according to the sequence numbers, the method comprising:

providing said processing unit on said printed circuit board;

providing a memory device on said printed circuit board, said memory device being in electronic communication with said processing unit, said memory device being adapted to store a most recent sequence number;

providing a power source on said printed circuit board separate from said processing unit;

electrically connecting said power source to said memory device to provide power to said memory device, wherein said memory device will store the most recent sequence number even if said processing unit is removed from said printed circuit board;

when each of the items is printed, storing the sequence number associated with the item in said memory device as the most recent sequence number;

receiving a request to print a selected one of said items; and

printing said selected one of said items only if it is determined that the sequence number associated with said selected one of said items is greater than the most recent sequence number currently stored by said memory device.

8. The method according to claim 7, wherein said power source is a battery.

9. The method according to claim 7, wherein said memory device is a CMOS memory device.

10. A method of protecting a processing unit included within a secure printing system from an attack wherein said processing unit is removed from an associated printed circuit board, comprising:

providing said processing unit on said printed circuit board, said processing unit having an internal memory;

providing a power source on said printed circuit board separate from said processing unit;

electrically connecting said power source to said internal memory to provide power to said internal memory; and

storing in said internal memory state information relating to one or more items printed by or to be printed by said secure printing system, wherein said internal memory is able to store said state information only if said power is provided to said internal memory;

wherein if said processing unit is removed from said printed circuit board, said power source will no longer be electrically connected to said internal memory and said state information will no longer be stored in said internal memory.

11. The method according to claim 10, wherein said power source is a battery.

12. The method according to claim 10, wherein said internal memory is CMOS memory.

13. The method according to claim 10, wherein said internal memory is provided with a key, wherein said internal memory is able to store said key only if said power is provided to said internal memory, wherein if said processing unit is removed from said printed circuit board, said power source will no longer be electrically connected to said internal memory and said key will no longer be stored in said internal memory, the method further comprising allowing said secure printing system to print one or more items only if said key is stored in said internal memory.