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Description  |
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FIELD OF THE INVENTION
The subject invention relates to a method and an apparatus for certifying
services obtained with the aid of a portable carrier, such as a memory
card.
BACKGROUND OF THE INVENTION
Although the magnetic card is widely used as a means of furnishing
services, purveyors of these services are made uneasy by the increasing
fraud in connection with services furnished because of stolen or
counterfeit cards.
The disadvantages of magnetic cards will be better understood from a brief
review of the manner in which a service is provided with a card with a
magnetic track, taking a payment card as an example.
First, proof that a transaction has taken place between a customer and a
vendor takes the material form of an acknowledgement or receipt, on which
the following information, in particular, is written: the amount of the
transaction and information that identifies the customer (name, account
number, etc.), picked up directly from the card (using the magnetic track
and/or information embossed on it), and information identifying the
vendor. After signature by the customer, the duplicate of the receipt is
given to the customer as proof, and the original is transmitted by the
vendor to its bank.
Second, the bank commences a series of operations, based on the information
written on the receipt, to debit the customer's account by the amount of
the transaction and credit the vendor's account by the same amount. Once
the debiting and crediting operations have been completed, the transaction
is validated.
From the above description of a transaction, two statements can be made:
1. The vendor has no means whatever at its disposal for detecting a stolen
or counterfeit card at the moment when the transaction is made, and
2. the bank has no means whatever at its disposal for proving, simply by
examining a receipt sent by a vendor, that the corresponding transaction
has been made using a stolen or counterfeit card.
Thus in the majority of cases, a fraudulent transaction cannot be detected
except by the customer, either after discovering his card has been stolen
or after his account has been debited for the amount of a transaction he
never made. The bank will then open an inquiry, but the results of that
are never available immediately.
Meanwhile, to reduce the number of fraudulent transactions, the vendor can,
as a control, verify that the name embossed on the card is the same one
written on some other piece of identity presented by the customer. This
kind of control does dissuade those committing petty fraud, but not
experienced swindlers. A second control is to verify that the number
embossed on the card is not included on a blacklist regularly updated by
banking entities. These controls are not effective for a card that has not
yet been reported stolen or for a counterfeit card that has not yet been
detected.
A solution to this problem is to have all the operations, from the request
for a service to the furnishing of the service, to be monitored, verified
and executed all at once. But, such a solution requires relatively
expensive equipment.
OBJECT AND SUMMARY OF THE INVENTION
By way of contrast, it is the object of the present invention to provide an
intermediate solution, where the control and verification operations are
performed at the moment the service is furnished, with sufficient
guarantees to the purveyor of the services, and where they can be
completed later after the service has been furnished, to certify that the
service has been furnished under proper conditions, both for the customer
and for the purveyor. The necessary equipment is furthermore limited to a
simple apparatus, which is neither bulky nor expensive and is
advantageously portable.
The invention proposes a method for certifying a service furnished with the
aid of a portable carrier such as a memory card coupled to a first
apparatus, characterized in that it comprises using the apparatus to
prepare a certificate comprising at least two data, the first being a
result calculated by the processing circuits based on parameters that are
internal and/or external to the card and on a secret key, and the second
being the aforementioned internal and/or external parameters that were
necessary for calculating the result, and recording this certificate on a
carrier as a means of proof that the service was furnished, and in that it
comprises, in a second step, recalculating, by the processing circuits of
a second apparatus, a result based on the internal and/or external
parameters of the certificate and on a secret key, and comparing this
result with the result of the certificate to certify that the service was
in fact provided with the aid of a card issued for obtaining this service.
In another feature of the invention, the result of the certificate is
calculated in a first step by the processing circuits of the card, and the
secret key is prerecorded in the memory of the card to prevent calculating
a plausible result in advance.
In still another feature of the invention, the result of the certificate
takes into account a variable parameter that is internal to the card, so
that two identical results will never be obtained for the same card.
In another feature of the invention, the certificate furnished in the first
step is recorded either on a carrier made of paper, such as a receipt, or
on a magnetic or electronic carrier.
Further advantages, characteristics and details of the invention will
become apparent from the explanatory description that follows, taken in
conjunction with the appended drawings provided by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of an apparatus for performing the
method according to the invention;
FIG. 2 shows an example of the certificate furnished by a purveyor after a
service has been furnished; and
FIG. 3 is a schematic representation similar to FIG. 1 illustrating a
further aspect of the invention for supplying a parameter to the apparatus
.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The example hereinafter described is an illustration of the method
according to the invention, in a payment application; however, the
principle of the invention remains valid no matter what kind of service is
furnished.
Referring now to FIG. 1, the apparatus 1 includes the following: a data
entry device 10, for example comprising a keyboard, a memory M1,
processing circuits T1 such as a typical microprocessor, and a display
unit 11, for example comprising light-emitting diodes.
All the circuits are connected to one another by a linking bus b1, which
carries control, address, and data signals.
This apparatus 1 is intended to receive a removable portable article 2,
such as a memory card including a memory M2 and processing circuits T2
connected via a linking bus b2. Such a card is described in particular in
French Pat. Nos. 2 401 459 and 2 461 301 (corresponding to U.S. Pat. Nos.
4,211,919 and 4,382,279, respectively) assigned to the assignee of the
subject invention.
The memory M2 of the card 2 includes at least three memory zones Z1, Z2,
Z3. The memory zone Z1 is inaccessible to writing and reading from
outside, and the memory zones Z2, Z3 are inacessible except for reading
from the outside.
Coupling of the card 2 to the apparatus 1 is done via two interfaces I/F
22, 12 that are connected to one another by an electrical connection L. By
way of example, these two interfaces are of the type described in the
French patent of the assignee of the subject invention, published as
French Pat. No. 2 490 367 (corresponding to U.S. patent application Ser.
No. 302,595, filed Sept. 15, 1981, now abandoned). The interface 12 of the
apparatus 1 may advantageously be equipped with the connector such as that
described in the French patent of the assignee of the subject invention,
published as French Pat. No. 2 445 560, (corresponding to U.S. Pat. Nos.
4,443,049 and 4,449,775) so as to enable the card 2 to be coupled in a
removable manner with the apparatus 1. Finally, the dialogue or data
transmission mode between the card 2 and the apparatus 1 may
advantageously be that described in French Pat. No. 2 483 713
(corresponding to U.S. Pat. No. 4,556,958) of the assignee of the present
invention.
The subject matter of the aforenoted patents and publications are hereby
incorporated by reference.
The apparatus 1 is supplied with power either from the mains or by an
autonomous battery 13 incorporated into the apparatus. It may
advantageously be embodied in a portable manner, because the circuits it
contains take up so little space.
The method according to the invention will now be described in terms of
this apparatus 1.
Generally, the apparatus used for putting a transaction into material form
and which is at the disposal of the vendor will fulfill three main
functions:
the first function is to authenticate the card presented by the customer,
to enable the vendor to detect a counterfeit card;
the second function is to identify the customer, by monitoring a code
assigned to the customer and entered into the apparatus, to enable the
vendor to detect a stolen card; and
finally, the third function is to calculate a result based on internal
and/or external parameters of the card.
Then, the vendor makes, or has made, a means of proof of the transaction on
a carrier of some kind (paper, electronic or magnetic) which in addition
to data specific to the transaction will also carry a datum, called a
certificate, comprising the aforementioned result and the parameters
necessary for calculating it.
Generally, the apparatus used to validate a transaction and placed at the
disposal of the banking entity will fulfill one main function, based on a
carrier serving as a means of proof and provided or forwarded by a vendor
or a customer. This function comprises recalculating the result of the
certificate based on the aforementioned parameters on the carrier, and
verifying that this result is indeed equal to that written on the carrier.
This kind of control enables the detection of counterfeit carriers made by
a defrauding vendor, or the detection of a correct carrier that is
nevertheless presented for cashing by some vendor other than the one who
originally issued the carrier.
The payment of the amount of the transaction is done in two steps.
The first step is performed by the vendor and has seven successive phases:
Phase 1
The customer, upon request by the vendor, inserts his card 2 into the
apparatus 1. If the card 2 is positioned correctly, it trips the
appropriate switch or circuit to cause a voltage to be supplied to the
apparatus 1.
Phase 2
The apparatus 1 performs a control of the customer's card 2. More
precisely, the apparatus 1 will pick up a datum I1 in the memory zone Z2
of the card 2 at a predetermined address. This datum I1 enables
verification of the status of the card; that is, it indicates whether
previous use of the card has occasioned some prohibition, or whether the
period of card validity has expired, and so forth.
Phase 3
The apparatus 1 will authenticate the card 2, or in other words verify
whether or not it is in the presence of a counterfeit card.
To do so, the apparatus 1 picks up a datum I2 in its memory M1 and encodes
this information prior to sending it to the card 2. The encoding is done
via the processing circuits T1 of the apparatus, which apply to the datum
I2 a public function with a public key of an algorithm with a public key
translated by a program P1 recorded in its memory M1.
This kind of algorithm is such that knowledge of the public function does
not enable deducing the inverse secret key function. The inverse secret
key function is recorded in the form of a program P'1 in the memory zone
Z1 of the card 2.
An encoded datum, that is, the datum 12 after its encoding by the apparatus
1, is transmitted to the card 2 and decoded by it via the processing
circuits T2 by executing the program P'1.
The datum decoded by the card 2 is transmitted to the apparatus 1, which
compares it with the original datum I2. If the two do not agree, then the
apparatus 1 has detected a counterfeit card.
For security reasons, the encoded datum is variable. To this end, the
apparatus 1 takes into account a variable datum I2, for example comprising
a random number.
Alternatively, the public key algorithm could be used in a different way.
The apparatus 1 sends a variable non-coded datum I2 (a random number, for
example) to the card 2. The card 2 encodes this datum I2 by the program
P'1, and the resulting datum is decoded by the program P1 of the apparatus
1.
Phase 4
The apparatus 1 identifies the person carrying the card 2 after this person
has entered into the apparatus 1 a datum assigned to him and recorded
earlier in the memory M2 of the card 2.
This datum is generally a confidential code Ce entered with the keyboard
10, and it is compared by the card 2 with a confidential code Ci
prerecorded in the memory zone Z1 of the card 2.
If identity does not exist between the two codes, or the two codes Ci, Ce
do not have a predetermined relationship, the apparatus 1 signals by some
suitable means that the person is in possession of a stolen card, or that
the person has made an error in entering his confidential code. In the
latter case, the person can begin the operation again, but after three
attempts, the card 2 generally invalidates itself and becomes unusable, by
assuming a predetermined status represented by the datum I1 written into
the memory zone Z2. It is this status that is controlled in the course of
phase 2 above.
The confidential code Ce entered into the apparatus 1 and assigned to the
person carrying the card 2 may be replaced by some other datum, such as:
a numerical code which reflects the signature of the person and is made by
a signature analyzer 14 connected to the apparatus 1; or
a numerical code which reflects the voice of the person, made by a voice
analyzer 15 connected to the apparatus.
Phase 5
The customer's card 2 calculates a result R with a view to making a
certificate C.
The certificate C comprises two data:
a first datum, which is the result R of the calculation performed by the
card 2 based on internal parameters prerecorded in the card 2 and/or
external parameters entered into the apparatus 1;
and a second datum, which comprises internal parameters PI and/or external
parameters PE necessary for calculating the result R, and which will then
be used by the banking entity to recalculate the value of the result R of
the certificate C.
By way of example, the internal parameters PI used by the card 2 to
calculate the result R of the certificate C are the following:
a fixed parameter PIF assigned to the card, for example its serial number
inscribed in the memory Z2 when the card 2 is manufactured;
and a variable parameter PIV, such as the datum that reflects the status of
the card after each use, this status of the card 2 being recorded in the
control memory zone Z3, and upon each transaction or use of the card, at
least one bit of this memory zone is modified internally by the processing
circuits T2 of the card.
By way of example, the external parameters PE communicated to the card 2
for calculating the result R of the certificate C are as follows:
a random datum PEA;
and a datum PEC assigned to the vendor, which is prerecorded in the memory
1 of the apparatus M1.
The calculation of the result R is done by the processing circuits T2 of
the card 2 in accordance with a program P2 precorded in the memory zone Z1
of the card that is not accessible from the outside, to keep it secret.
In a preferred mode for calculating the result R, the program P2 takes into
account at least one variable parameter for each calculation, so that two
results R will never be identical, in particular for the various results
calculated by the same card. This variable parameter may advantageously be
the internal parameter PIV of the card that reflects the status of the
card and is mofified each time it is used.
The use of this variable parameter PIV prevents the possibility that a
defrauder may be able to reuse a result R that could be recognized as
valid, even though based on a fraudulent transaction.
To increase security, the program P2 for calculating the result R also
takes into account a secret key S, prerecorded into the memory zone Z1 of
the card, to prevent a defrauder from being able to calculate a result R
in advance.
By way of example, the result R is calculated on the basis of: the variable
internal parameter PIV that specifies the status of the card; the internal
parameter corresponding to the serial number of the card, or any other
parameter assigned to the card, so that two cards having the same status
at a given instant can calculate two different results; an external
parameter PEC assigned to the vendor so as to personalize the result R, to
prevent a vendor from using for his own benefit a result R calculated in
the course of a transaction performed for some other vendor; and a secret
key S.
In conclusion, the certificate C causes the following to become visible:
the result R previously calculated,
and all the parameters PI, PE, except for the secret key S, that were used
in calculating the result R.
It is important to note that a certificate C is not absolutely
confidential, and that two certificates C are never identical.
By way of example, the program P2 that enables calculation of the result R
of a certificate may be an algorithm for reversible and public encoding,
such as the algorithm known by the name "DES".
Phase 6
The vendor furnishes proof of the transaction by way of a carrier, such as
a piece of paper or receipt 3, on which the following information, in
particular, is written, referring to FIG. 2:
the amount X1 of the transaction;
the date X2 of the transaction;
the ordinal number X3 of the receipt,
the identity X4 of the customer (name, banking entity and number of account
to be debited) picked up from the card;
the identity X5 to the vendor (name, banking entity and number of account
to be credited;
and the certificate C comprising a result R and the parameters PI, PE
necessary for calculating it.
The certificate C, once it has been calculated, is displayed on a unit 11
of the apparatus 1, and the vendor copies this onto the receipt 3.
However, it may be provided that the certificate C is posted automatically
on the receipt 3.
Phase 7, the final phase
The status of the card is modified in the memory zone Z3 by the processing
circuits T2, and the card 2 is taken back out of the apparatus 1, thereby
terminating the supply of voltage to it.
The second step is performed in a single phase, on the part of the banking
entity.
The receipt 3 thus made is then sent by the vendor to its banking entity,
which has an apparatus 1 similar to that of the vendor and also has a
control card similar to the customer card 2, which is coupled to the
apparatus 1 for recalculation of the result R of the certificate, based on
the parameters posted on the receipt 3. Once the control card, which is
similar to the customer card 2, is coupled with the apparatus 1, an
operator, via a keyboard 10 of the apparatus 1, enters the value of the
centificate C as it is posted on the receipt 3 and comprising the result R
and parameters PI, PE that were used to calculate it. This value is
recorded in the memory M1 of the apparatus 1, and the parameters of the
certificate C are transmitted to the control card.
The control card similar to customer card 2 contains the same program P2
for calculating the result as the program P2 contained in the customer
card 2 and also the same key as the secret key S of the customer card 2.
The processing circuits of this control card, which are the same as the
circuits T2 of the customer card 2, calculate a result R, and the control
card or the apparatus 1 verifies that this result does in fact agree with
that of the receipt 3. If it does not agree, the banking entity will have
detected a false receipt 3 based on a fraudulent transaction. This
verification is done by a comparator circuit of the control card which is
the same as the comparator circuit 16 of the customer card 2, or by a
comparator circuit 17 of the apparatus 1.
Furthermore, the customer or the vendor can always have a transaction
verified by presenting the duplicate of the receipt to the banking entity,
which can immediately monitor the validity of the receipt by recalculating
the result of the certificate.
In another feature of the method according to the invention as shown in
FIG. 3, when the calculation of the result R of the certificate C takes
into account an external parameter assigned to the vendor, this parameter
PEC is not entered by the vendor. More precisely, the vendor has a card 4
similar to the previous card 2, and which contains this parameter. For the
apparatus 1 to be able to function, an initializing operation must be
performed, which comprises coupling the card 4 with the apparatus 1,
having the apparatus 1 pick up the parameter in the card 4 assigned to the
vendor, and storing this parameter PEC in the memory M1 of the apparatus
1.
In the phase when it is used for calculating a certificate, the apparatus 1
will transmit this parameter PEC directly to the customer's card 2.
Preferably this initializing step is not done simply once and for all, nor
prior to each transaction, but it must be repeated systematically, for
example whenever the battery 13 of the apparatus is empty, whenever the
apparatus has been in operation for a predetermined time, or whenever the
apparatus has performed a given number of transactions.
This greatly reduces the possible incentive to steal such an apparatus.
In the above example, the certificate C is posted on a carrier (receipt)
made of paper, which serves as a means of proof, but the principle of the
invention remains valid if the carrier is electronic (memory) or magnetic
(tape). In that case, the certificate C is recorded on the electronic or
magnetic carrier at the end of the first step, and then the contents of
this carrier are removed, for example daily or after every n transactions,
and transmitted to a central system for certification (second step).
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