~ ~ 3 ~ 8 TITLE: FAULT TOLERANT SMART CARD
-: 3 4 rrECHNICAL FIELD
The present invention relates to a fault tolerant smart card and, more specifically, to a fault tolerant smart ¦ card ~hich may find particular application in the postage meter "
:' 9 10 ~IBACKGROUND AND OBJECTS OF
: THE INVENTION
.11 , 12Integrated circuit or so-called "intelligent" or 13 "smart" cards which include a microprocessor and memory are ;~
14 commercially available and are useful in many applications. Of increasing importance is the ability of smart cards to securely 16 1. transport monetary funds, including transportation of postal ~ ~ 17 ll funds or information relating to postage funds. Sae, for ~ 18 example, U.S. Patent No. ~,980,542 entitled "Postal Charge 19 1 Accounting Systam" wherein departmental postage meter use information is stored in smart card memory, and U.S. Patent No.
~ 21 li 4,978,839 entitled "Puatage Meter ~alue Card System" wherein ;, 22 l¦ postage meter funds are transferred from a value card center to ~ 2 3 1 a postage meter ~or recharging the postage meter vault.
:` ~ 24 ~` 25 26 j Given the increasing importance of information stored . 27 lin smart card memory, the adverse effects of a malfunctioning 28 l smart card can be quite costly. ~herefore, it wOula be highly .. 29 .,, , ~
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~3~5~8 l desirable to provide a smart card having increased reliability. It would also be highly desirable to provide a 3 smart card which may be accessed by service personnel even were 4 a card mal~unction to occur. In this manner, monetary funds S stored in the card would not be ~lost~ due to card malfunction.
6 Therefore, it is an object of an aspect of the 7 present invenkion to prQvide an improved smart card.
8 It is an object of an aspect o~ the invention to 9 provide a faul~ tolerant smart card.
It is an object of an aspect o~ the invention to l provide access to information retained in memory of a smart 12 card which suffers a malfunction.
13 These and other highly desirable objects and 14 advantages are obtained in a convenient yet secure fault tolerant smart card.
16 Objects and advantages of the invention are set forth 17 in part herein and in part will be obvious herefrom, or may be 18 learned by practice with the invention, the same being realized 19 and attained by means of the instrumentalities and combinations pointed out in the appendsd claims.
SUMMARY QF THE INVENTION
23 In accordance with the present invention a fault 24 tolerant smart card is provided having primary functional units including a standard ISO interface, a primary microcontroller, 26 main memory including ROM, RAM and E~PROM, a clock generator and a power source. In addition to its normal smart card 28 functions the primary microcontroller addresses an access 29 account register and a microcontroller fault detector which, in turn, addresses an exception register. Secondary smart card ,~
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1 ¦~ functional units are provided including a secondary 2 ~¦ microcontroller, secondary memory which may include ROM and 3 ~ associated check bits, a funds remaining shadow register, the b access account register, the microcontroller fault detector, and the exception condition register. A private access port is 6 also provided. All of the secondary units requiring power 7 support are connected to an alternate battery power source.
8 The secondary microcontroller is connected to the primary and 9 secondary clock units, the microcontroller fault detector and the funds remaining register. The secondary microcontroller ll addresses the secondary memory and has read-only access to the 12 main memory.
13 In normal operation the primary and secondary 14 microcontrollers operate synchronously and execute in parallel identical instructions from the same memory store, but with the 16 secondary microcontroller having read-only access to the main 17 memory.
18 Should the microcontroller fault detector sense a 19 fault in either of the main or secondary microcontrollers, as evidenced by an inconsistency between microcontroller signals, 21 the exception register will be written into. When this occurs 22 the primary microcontroller will be maintained in a frozen 23 state and the secondary microcon-troller will be released from 24 the main memory to address the secondary memory and run known test patterns. Should a fault occur during the test the 26 secondary microcontroller is assumed to be faulty and the main 27 microcontroller will be permitted to continue processing. Of 28 course, the user miqht be notified that card service and/or 29 replacement is required.
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1 1 On the other hand, if no error occurs during the test 2 1 then the main microcontroller is assumed to be faulty, the card remains inoperable, and the user is notified by an appropriate 4 flag that a card fault condition exists.
Advantageously, the private access port perrnits 6 service personnel to directly access the secondary microcontroller, the funds remaining register, the access 8 account register and the exception condition register. Service 9 personnel might also make use of the secondary microcontroller, such as to access in read-only fashion the main memory. In the ll preferred embodiment including check bits the check bits would 12 detect and circumvent any single bit failure in the secondary 13 memory.
14 Thus, it will readily be appreciated that the fault tolerant smart card according to the present invention 16 advantageously provides a smart card capable of detecting and 17 circumventing a single bit or single path failure.
18 Notwithstanding such a failure, the fault tolerant smart card lg remarkably provides "back-door" access through a private access port to important information held in the smart card.
21 Advantageously, the person acquiring access through the private 22 access port is able to determine the amount of any funds 23 remaining in the card and access other important information in 24 the card main memory. As a further advantage of the present invention the primary functional units communicate via the 26 standard ISO interface in a traditional manner. Therefore, the 27 fault tolerant smart card in accordance with the invention may 28 be used in conjunction with existing, unmodified equipment. By 2g way of example only, the fault tolerant smart card according to ,,"'.
the pre~ent invention may find particular application in the systems disclos~d in the aforementioned patent applications.
Other aspects of this invention are as ~ollows:
A ~ault tolerant smart card comprising:
a standard input-output interface;
clock means for providing a time reference during smart card operations;
,., main memory means for storing program and data information;
first microcontroller means connected to said interface, said clock means and said main memory : means for performing normal smart card functions;
.--secondary microcontroller means connected to said first microcontroller means, said clock means, :.
.,'. : said main memory means and to secondary memory :
m~ans for performing normal smart card functions '~ in synchronization with said first ;~ : microcontroller means;
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microcontroller error detection means connected to said first microcontroller means and said secondary microcontroller means for detecting a failure of either of said first or secondary microcontrollers; and "' primary power supply means eonnected to said :
~,, first microcontroller means.
~ A fault tolerant smart card comprising:
;', a standard input-output interface;
., . clock means for providinq a time reference during smart card operations;
. main memory means for storing program and data . ~
:. first microcontroller m~ans connected to said interface, said cloc~ means and said main m~msry means for performing normal smart card functions;
~", .~ ~ secondary microcontroller means csnnected to said . ........................................................................ .
~: first microcontroller means, said clock means, :.:
` ~ said main memory means and to secondary memory ,:~
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means, said secondary microcontroller means performing normal smart card functions in synchronization with said first microcontroller means;
microcontroller error detection means connected to said first and secondary microcontroller means for detectinq a discrepancy bet~een said first and secondary microcontroller means; and private access port means connected to said secondary microcontroller for providing private access to the fault tolerant smart card.
It will be understood that the foregoing general description as well as the following detailed description are exemplary and explanatory of the invention but are not restrictive thereof.
RIEE DESCRIPTION OF THE DRAWING
The accompanying drawing, referred to herein and constituting a part hereof, illustrates in schematic block ; diagram form the preferred embodiment of a fault tolerant smart ; card in accordance with the present invention.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawing, labelled as Figure 1, there is shown a schematic block diagram illustration of the fault tolerant smart card 10 in accordance with the invention.
As shown, smart card 10 includes a set of primary functional units including a standard ISO type interface 12, a microcontroller unit 14, addressable read-only memory (ROM) 16, random access memory (RAM) 18, electronically erasable programmable read-only memory (EEPROM) 20, primary and secondary clock generators 22, 26, respectively, and a primary power source 24. The preferred General Electric smart card referred to in the aforementioned patent applications derives power through the ISO interface, as shown, but an external primary power supply is not critical to the present invention.
The foregoing elements, interconnected as shown, comprise the ; primary functional units for carrying out normal operation of the smart card.
1 I In addition, secondary functional units are provided 2 ¦ for fault tolerant card support. I'he secondary units include a 3 ~ second clock generator 26 connected to an alternate battery 4 I power source 28 and to both microcontrollers 14, 30. The secondary microcontroller is connected to secondary memory 32, 6 a microcontroller fault detector 36, and a funds remaining 7 shadow regis-ter 38. Preferably, check bits 34 are provided in 8 association with secondary memory 32 to monitor single bit 9 failures within the secondary memory. As shown, the secondary microcontroller is connected in an addressable manner to ROM 32 ~ ll and to funds remaining register 38. Secondary microcontroller 1 12 30 is also connected to a private access port 44 and has 13 read-only access to main memory 20. Secondary microcontroller 14 30 is supported by primary power source 24 and alternate battery source 28. An access account register 40 and an 16 exception condition register 42 addressed by the microcontroller fault detector are also provided. Each of 18 funds remaining register 38, access account register 40, and 19 exception condition register 42 are also connected to private access port 44 and are supported by battery source 28.
21 Secondary memory 32 is also supported by battery source 28 and 22 is connected to exception condition register 42. Access 23 account register 40 is addressed by primary microcontroller 14 24 and is written into after each card use to maintain a history trace of the identity of the user, the memory address accessed, 26 and the information stored at that address.
27 So constructed, the present smart card circuit 28 provides detection and circumvention of single bit and single 29 path smart card faults. During normal operation both rnicrocont~ollers 1~, 30 work in a synchronous mode of 131~408 l operation to execute in parallel identical instructions from 2 1I the same memory store. After each transaction secondary 3 ~ microcontroller 30 updates funds remaining register 38 to 4 ¦¦ provide a running summary of the funds that remain stored in ~ the card.
6 ~ Should a discrepancy occur hetween the main and 7 secondary microcontrollers the microcontroller fault detector, ~ here shown as exclusive "OR" gate 36, would trigger a high 9 output signal, thereby writing into exception condition register 42. If the exception register 42 is written into, ll program information in secondary memory 32 will direct 12 secondary microcontroller 30 to release main memory 16, 18, 20 13 and run known test patterns stored in secondary memory 3~.
14 ¦ During this time main microcontroller 14 remains in a fro~en state. Should a fault occur during the test, secondary 16 processor 30 is assumed to be faulty and main processor 14 is 17 permitted to continue processing. However, if no ~aults are 18 found during the known test pattern, the main processor 14 is 19 assumed to be faulty and the user is notified of a fault condition. Thereaft'er, information access is limited to 21 proprietary interface 44, which is preferably available only to 22 service personnel. Notwithstanding a main processor fault, 23 service personnel may access each of the funds remaining 24 register 38, access account register 40, and exception register 42 through private access port 44. Main memory 16, 18, 20 26 might also be accessed through port 44 if secondary 27 microcontroller 30 remains viable. In this regard, secondary 28 memory 32 is preferably provided with associated check bits, 29 sometimes referrecl to as "Hemming Bits", to circ-lmvent any bit failures within secondary memory 32.
1 Thus, the fault tolerant smart card according to the 2 ~ invention substantially ellminates the risk that funds and/or 3 accounting information stored in the card will be lost due to 4 card failure. Indeed, should a card failure occur, service personnel may simply access the remaining funds amount and 6 other information held in main memory and transfer this 7 information to a new smart card or other recording medium. In 8 this manner the customer is assured that monetary funds and 9 inEormation will not be compromised due to a smart card malfunction. As will be readily appreciated, this capability 11 will avoid the deleterious effects to customer relations that 12 might otherwise result from such card failures.
13 Thus, the fault tolerant smart card according to the 14 present invention advantageously detects smart card failures lS and, notwithstanding such a failure, permits private access to 16 important information stored in the faulty card.
l7 To the extent not already indicated, it will be 18 understood that the invention in its broader aspects is not 19 limited to the specific embodiments herein shown and described ?O but departures may be made therefrom within the scope of the 21 accompanying claims, without departing from the principles of 22 the invention and without sacrificing its chief advantages.