AU704773B2

AU704773B2 - Method of authenticity checking of a prepaid payment means used in a transaction

Info

Publication number: AU704773B2
Application number: AU11404/97A
Authority: AU
Inventors: Youssef Cammoun; Herve Hillion
Original assignee: Landis and Gyr Technology Innovation AG
Current assignee: IP-TPG HOLDCO Sarl
Priority date: 1995-12-11
Filing date: 1996-12-03
Publication date: 1999-05-06
Anticipated expiration: 2016-12-03
Also published as: WO1997022093A1; EP0870286A1; AU1140497A; CH690530A5

Description

LLIL b II -1 17 WO 97/22093 PCT/EP96/05347 Method of authenticity checking of a prepaid payment means used in a transaction The invention relates to a method of authenticity checking of a prepaid payment means used in a transaction, as set forth in the classifying portion of claim 1.

To make sales transactions easier, cash-less payment means are being increasingly frequently used in automatic machines for the sale of goods or services, such as for example telephone stations or automatic machines for dispensing travel cards, food or drink. Cash-less payment means are for example chip cards, magnetic cards and optical cards. When purchasing an article or a service, the cards are put into a card slot of a reading device of the automatic sales machine and checked in regard to their authenticity or the cash value which they still have, in the automatic sales machine or in a central station. In the event of a positive check result, that is to say when the payment means is found to be authentic and has sufficient money value, purchase of the article or service is enabled and the money value of the payment means is reduced by the value of the article or service purchased.

The following kinds of cash-less payment means are known: 1. Payment means of a first generation are characterised by the presence of a plurality of erasable stored value units ("tokens") which 25 embody an equivalent of the article or service to be purchased. They are easy to handle but they can only be used with difficulty for services from different suppliers. The value units or tokens often comprise stored bytes, that is to say 8 bit code words which are for example a function of a card manufacture date and an algorithm which is kept secret. The 30 forgery-proofness of the first-generation payment means depends exclusively on the difficulty with which they can be simulated, that is to say copied.

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j 2 2. Payment means of a second improved generation can be used for services from different suppliers. Their value is embodied by the content of a counter which is protected from incrementations and which can be decremented upon the purchase of an article or service and the count unit of which corresponds to the value of the smallest transaction which is possible for the use in question. Unfortunately the second-generation payment means do not permit a high degree of diversification of a call-up signal which is used in the authenticity checking procedure.

3. Payment means of a third generation are based on the concept of the second-generation payment means. The authenticity recognition system thereof relies on the use of a complex call-up signal, a code key which can be organised to involve a wide range of variations, and an algorithmic function. In that case the call-up signal is a function of a random signal, identification and/or security details of the payment means and an accounting value of the payment means, which latter represents its money value which is still available. The identification and/or security details include for example a manufacturing date and/or a manufacturing batch number. Further details in regard to such payment means can be found in the European Standard prEN 726-2 "Identification card systems Telecommunications integrated circuit(s) cards and terminals Part 2", Annex A, July 1995.

The object of the present invention is to improve the safeguard against fraud in respect of the known authenticity checks and to make same dependent on the size of a money loss which threatens in the event of a forgery.

In accordance with the invention that object is attained by the features recited in the characterising portion of claim 1. Advantageous configurations of the invention are set forth in the appendant claims.

Embodiments of the invention are illustrated in the drawing and described in greater detail hereinafter. In the drawing:

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A1.1 i_4 3 Figure 1 is a diagrammatic view of a card reader with an inserted chip card. assuming that the card reader includes a card evaluation unit, and Figure 2 is a diagrammatic view of an optical feature, irradiated with a light beam, of a cash-less optical payment means.

The cash-less payment means used in the method according to the invention are preferably chip cards, magnetic cards or optical cards.

When using chip cards, an associated card reader 1 which serves for reading and evaluating the chip cards is preferably of the diagrammatic structure shown in Figure 1. The card reader 1 is a part of an automatic article and/or service sales machine which is not shown in Figure 1. Upon the purchase of an article or a service, for payment purposes a chip card 2. as a cash-less payment means, is inserted into a card slot of the card reader 1. Arranged on the chip card 2 or preferably in the card reader 1 are a random generator 3 for producing random bit sequences 4 and a control logic 5 for releasing the latter. It is assumed in Figure 1 that the two units 3 and 5 as well as a card evaluating device 6:7 are provided in the card reader 1. The card evaluating device 6; 7 includes an arrangement 6 for producing a reference value authenticity signal 8 and a comparison circuit 7. Provided on the chip card 2 is a gating switching arrangement 9 for producing a call-up signal 10 which is a function of a released random bit sequence 11, identification and/or security details 12 of the chip card 2, and an accounting value 13. For that purpose the last two are applied to a first and a second input respectively of the switching arrangement 9 while the first feeds, from the output of the control logic 5, a third input of the switching arrangement 9. The accounting value 13 is the stored money value, which is still available of the chip card 2. The callup signal 10 which occurs at the output of the switching arrangement 9 is a serial input signal of a shift register 14 which is provided with feedbacks and in which at the beginning a code key is stored and which is for example of a 48 bit length. The shift register 14 provided with feedbacks embodies an algorithm of the chip card 2. An output signal produced at a serial

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4 output of the shift register 14 is an answer signal 15 of the shift register 14 to the call-up signal 10. It is a function of the code key, the algorithm and the call-up signal 10 and it is thus also a function of the random bit sequence 11, the identification and/or security details 12 and the accounting value 13. The answer signal 15 is an authenticity signal 17 which is compared to the reference value authenticity signal 8 in the comparison circuit 7. It is assumed in Figure 1 that the two signals 8 and 17 are fed in bit-serial manner to respective ones of two inputs of the comparison circuit 7. The reference value authenticity signal 8 is produced in the arrangement 6 of the card evaluating device 6:7 in the same or a similar manner to the way in which the authenticity signal 17 is produced on the chip card 2, the value of the article or service to be purchased being involved in place of the accounting value 13. If the value of the article or service to be purchased is smaller than the accounting value 13 and if the other parameters of the call-up signal and the key code are the same, the comparison circuit 7 enables purchase of the article or service and the accounting value 13 is reduced by the value of the purchased article or service.

In order to reduce the risk of fraud the output signal of the shift register 14, that is to say the answer signal 15 thereof to the call-up signal 10. has very many bits in the known third-generation chip cards, all of which bits are used in the authenticity checking procedure, which has the disadvantage that the authenticity comparison operations take a relatively long time as the duration thereof is a function of the number of bits. The risk of fraud when checking a single n-bit code word is known to be 1/(2 n and is very small only when n is very great. When using for example 16 output bits of the shift register 14 the risk of fraud of the i known chip cards is thus 1/(216). i In the case of so-called LVPOS ("Low Value Point Of Sales") services and articles the amount owed upon the purchase of a service or article is charged in one go so that limiting the risk of fraud is particularly important and must be the primary endeavour. That is the case in q m "WM, 1,nft, r'j~ P 1. Va particular if the amount owed is not negligibly small, as for example in the case of automatic sales machines for dispensing meal and railway cards.

In order to achieve this, in the method according to the invention, just as in the third-generation method, the authenticity checking procedure involves triggering the answer signal 15 in reply to the call-up signal the answer signal 15 in turn serving to produce the authenticity signal 17 which is used in the subsequent authenticity comparison procedure. In contrast to the known method however the diversity of the answer signal in the method according to the invention is a function which increases with the value of the transaction. For that purpose the authenticity checking operation includes a plurality of authenticity comparison procedures which are each effected with their own respective associated answer signal the number of authenticity comparison procedures N being a function which increases with the value of the transaction. The authenticity comparison procedures are preferably effected in succession in respect of time. If the prepaid payment means is the chip card 2 as shown in Figure 1 then the respective answer signal 15 comprises at least 1 bit and at a maximum for example 16 bits. The number n of bits of the answer signal 15 is in that connection a measurement in respect of the diversity thereof. In order to keep down the amount of time for each authenticity comparison procedure, n is to be selected to be as small as possible in spite of the 16 bit length of the output signal of the shift register 14. It is assumed hereinafter that n 4. Accordingly, for each sales transaction, a plurality of.

namely N, authenticity comparison procedures are implemented with a respective 4 bit length of the associated answer signal 15. Excluding 4 accidental equality, the latter is different for each authenticity comparison procedure as it is dependent inter alia on the respective random bit sequence 11. The risk of fraud in a single authenticity comparison procedure is admittedly relatively great at 1/(24) 1/16, but that of the total authenticity checking operation, that is to say all N authenticity ~comparison procedures together, is very small at 1/( 16 )N and Ki rI A.

more specifically decreases in proportion to an increasing value of N and thus an increasing value of the sales transaction.

The method according to the invention is also used to advantage if the value of the purchased article or service is made up of a very large number of small partial amounts and for example increases stepwise in the course of time, with the partial amounts each being charged immediately that they fall due and not just at the end of the transaction. That is for example the case with telephone calls where the call costs increase after each unit charge pulse by a relatively small partial amount which is charged to the caller immediately in each case and not just at the end of the call. If the transaction is a telephone service, in accordance with the invention a respective authenticity comparison procedure is effected in respect of each unit charge pulse so that, during the duration of the entire transaction, a plurality of. more specifically N, authenticity comparison procedures occur in a time-staggered fashion, each with an associated answer signal 15 which is generally different and the number n of bits of which can here be readily chosen at a low value, for example once again equal to 4 bits, as the value of a unit charge pulse is generally relatively low and thus an increased risk of fraud can be accepted in regard to the first unit charge pulses. The value thereof increases with the duration of the telephone service, but there is also an increase in the number of unit charge pulses and thus the number N of authenticity comparison procedures, which in turn results in a reduction in the risk of fraud as 1 2 The latter is thus relatively great at the beginning of a telephone call, at 1 2 but it decreases in the course of the call in proportion to the increasing length of the call, that is to say the greater that its value is and the greater that N is.

If the prepaid payment means is an optical card, it is irradiated with a light beam in the reading operation in the card reader at a predetermined angle, the light beam then being for example reflected in one or more given predetermined directions, in accordance with the respective optical security feature present on the card. In Figure 2 reflection takes .1 place in a single direction. Instead of reflection, diffraction or refraction of the light beam iS also possible. In that case fraud is possible for example by irradiating the optical security feature with a light beam which is reflected in all directions, that is to say also in the predetermined directions. The method according to the invention can also be used in that case insofar as the light beam used when reading the optical card is modulated and a number of features produced by means of the modulation effect is a measurement in respect of the variety of the answer signal. If the light beam is subjected to binary modulation, the number of pulses produced in that way is preferably a measurement in respect of the variety of the answer signal. In this case the pulses can be amplitude, frequency or phase pulses, p ST1 /1

Claims

1. A method of authenticity checking of a prepaid payment means used in a transaction with an answer signal (15) which is produced in the authenticity checking operation in response to a call-up signal (10) and which is an authenticity signal (17) that is used in a subsequent authenticity comparison procedure, characterised in that the variety of the answer signal (15) is a function which increases with the value of the transaction.

2. A method according to claim 1 characterised in that the authenticity checking operation includes a plurality of authenticity comparison procedures which are each effected with their own respective associated answer signal (15) and that the number of authenticity comparison procedures is a function which increases with the value of the transaction.

3. A method according to claim 2 characterised in that the authenticity comparison procedures are effected in succession in respect of time.

4. A method according to claim 3 characterised in that an authenticity comparison procedure is effected for each unit charge pulse if the transaction is a telephone service.

A method according to one of claims 1 to 4 characterised in that the prepaid payment means is a chip card

6. A method according to claim 5 characterised in that the answer signal (15) respectively comprises at least one bit and that the number (n) of bits is a respective measurement of the variety of the answer signal 9

7. A method according to claim 6 characterised in that the answer signal (15) is an output signal of a shift register (14) which is provided with feedbacks and in which a code key is stored and whose input signal is a function of a random bit sequence identification and/or security details (12) of the chip card and a money value which is still available.

8. A method according to one of claims 5 to 7 characterised in that the answer signal (15) is the authenticity signal (17) which is respectively used for the authenticity comparison procedure.

9. A method according to one of claims 1 to 4 characterised in that the prepaid payment means is an optical card.

A method according to claim 9 characterised in that a light beam which is used when reading the optical card is modulated and a number of features produced by means of the modulation effect is a measurement of the variety of the answer signal.

11. A method according to claim 10 characterised in that the light beam is st:jected to binary modulation and the number of pulses produced in that way is the measurement in respect of the variety of the answer signal,

12. A method according to claim 11 characterised in that the pulses are amplitude, frequency or phase pulses.

13. A method according to one of claims 1 to 4 characterised in that the prepaid payment means is a magnetic card. Si ii nk i

14. A method of authenticity checking of a prepaid payment means substantially as herein described with reference to Figs. 1 and 2. DATED this Sixth Day of July 1998 Landis Gyr Technology Innovation AG Patent Attorneys for the Applicant SPRUSON FERGUSON i T o ei S- i