Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a magnetic recording
medium and a method of determining whether the medium is true
or false, and more particularly to an improvement in security
of the magnetic recording medium.
The present invention is adapted to a magnetic recording
medium, e.g., a magnetic card requiring an unfair use
preventing function and a forgery and alteration preventing
function.
Conventionally, the security or protection of the
magnetic card, for example, is improved by a method wherein
azimuth magnetic recording (this corresponds to the case of
Y ~ 90 at the magnetic recording described in Fig. 1 of
Canadian Patent No. 1,193,365, issued September 10, 1985, to
EMI Li~ited) is carried out to prevent the forgery by a usual
reader-writer, a method using a magnetic bar code, or a
method using a magnetic mark. The azimuth magnetic recording
and reproduction are effected by means of a magnetic head as
disclosed in U.S. Patent No. 4,639,812, issued January 27,
1987, to Nakamichi Corporation.
However, the conventional methods as mentioned above
require a special magnetic card and a special reader-writer,
causing complication of a card system.
According to one aspect of the present invention, there
is provided a magnetic recording medium having a magnetic
layer, said magnetic layer including at least one magnetic
recording track formed in said magnetic layer in one
direction, at least one edge of said recording medium being
oriented perpendicular to the direction of the recording
track and bearing a truth determining code, said code
comprising a combination of polarities of magnetic poles
formed at predetermined positions of the magnetic layer, said
truth determining code having a predetermined relationship to
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the contents recorded in the recording track.
Preferably, the predetermined positions include both
edges of the recording track.
According to another aspect of the present invention,
there is provided a method of determining whether a magnetic
recording medium having a magnetic layer and at least one
magnetic recording track formed in the magnetic layer is
authentic, comprising the steps of:
detecting polarities of magnetic poles formed at
predetermined positions of the magnetic layer at at least one
edge of the medium perpendicular to a direction of the
recording track so that a truth determining code is formed
thereby, said code comprising a combination of polarities of
magnetic poles formed at predetermined positions of the
magnetic layer;
reading the contents recorded in the recording track to
form a comparative code to be collated with the truth
determining code;
collating the truth determining code with the
comparative code; and
determining the authenticity of said medium by
determining whether the truth determining code has a
predetermined relationship to the comparative code.
Preferably, the detecting and reading steps are carried
- 30 out by the same magnetic head.
As mentioned above, the truth determining code is
recorded at the edge of the magnetic recording medium.
Therefore, it is hard to read the truth determining code by a
magnetic viewer or the like. Furthermore, whether the
magnetic recording medium is true or false is determined by
collating the combination of the magnetic polarity at the
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edge with a proper combination. Therefore, as far as the
system of the truth determining code is unknown, it is
impossible to forge or alter the magnetic recording medium.
This invention will be further illustrated by way of the
accompanying drawings, in which:
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Fig. 1 is a schematic plan view of a first preferred
embodiment of the magnetic recording medium according to the
present invention:
Fig. 2 is a schematic plan view of a second preferred
embodiment of the magnetic recording medium according to the
present invention:
Fig. 3 is a schematic plan view of a third preferred
embodiment of the magnetic recording medium according to the
present invention:
Fig. 4 is a schematic diagrammatic view of a reader-
writer for carrying out a preferred embodiment of the truth
determining method according to the present invention; and
Fig. 5 is a waveform chart of sensor outputs of magnetic
heads.
There will now be described some preferred embodiments
of the present invention with reference to the drawings.
Fig. 1 ic a schematic plan view of a first preferred
embodiment of the magnetic recording medium according to the
present invention.
Referring to Fig. 1, a magnetic card 1 is provided with
a magnetic layer whose magnetic polarity is oriented in one
direction. The magnetic layer is provided with three
magnetic tracks Tl - T3. As appreciated from Fig. 1, the
magnetic polarity at opposite edges of the track T2 only is
inverted,
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for example. Therefore, as will be hereinafter described,
the combinatlon of N-S-N or S-N-S may be obtained by detecting
the magnetic polarity at the edges of the tracks, and this
combination may be utilized as a -truth determining code for
the magnetic card. In this embodiment, the number of combina-
tion is 2 = 8, that is, eight kinds of discrimination may
be effected.
The truth determining code may be decided in accordance
with a desired content recorded on the tracks Tl - T3, such as
personal information and amount of money. For example, when
the magnetic card 1 is a prepaid card, a remainder changes
every time the card is used. Therefore, the truth determining
code is decided in accordance with the remainder, and this
code is updated every time the card is used. Accordingly, if
the remainder is unfairly altered, such alteration can be
easily discovered.
The magnetic card may be easily manufactured by forming
the rnagnetic layer to be usually adopted and arbitrarily
inverting the magnetic polarity. Thus, any special processes
or steps are not necessary.
Fig. 2 is a schematic plan view of a second preferred
embodiment of the magnetic recording medium according to the
present invention. In this embodiment, a data track Tl is
formed independently of tracks Tal and Ta2 including the
truth determining code.
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Fig. 3 is a schematic plan view of a third preferred
embodiment of the magnetic recording medium according to the
present invention. In this embodiment, the magnetic polarity
at edges El - E6 only is inverted or non-inverted, and such
is utilized as the truth determining code. In this case, the
number of combination of the polarity becomes 2 .
As the inversion or the non-inversion of the magnetic
polarity at the edges only is utilized, such cannot be read
by a magnetic viewer. Further, in the case that the magnetic
polarity at the edges is not inverted with respect to the
orientation of the magnetic polarity of the magnetic layer,
it is greatly hard to read a position of the truth determining
code.
Fig. 4 is a schematic diagrammatic view of a reader-writer
for carrying out a preferred embodiment of the truth determin-
ing method according to the present invention, and Fig. 5 is
a waveform chart of sensor outputs of magnetic heads.
Referring to Fig. 4, the magnetic card 1 is a prepaid
card as shown in Fig. 1, and has three magnetic recording
tracks at whose edges the truth determining code is recorded.
The magnetic card 1 is movable by a transfer means 10
in the directions as depicted by a double-headed arrow in
Fig. 4, and the information recorded on each track is adapted
to be read by magnetic heads MS1 - MS3.
Signals Sl - S3 read are adapted to be input to a signal
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processing unit 11 where signal processing such as
amplification and AD conversion is carried out, and the
signals thus proces~ed are adapted to be stored in a memory 12.
The information stored in the memory 12 is processed,
e.g., calculated or modified by a control unit 13 as required.
The control unit 13 is connected to an input unit 14 such as
a ten-key unit for inputting a purchase price, for example.
The control unit 13 is also connected to a sensor 15 for detect-
ing the edges of the card 1, a display unit (not shown), etc.
The operation of this embodiment will now be described
with reference to Figs. 4 and 5.
First, when the card 1 is inserted into the reader-writer,
the transfer means 10 is operated by the control unit 13 to
draw the card 1 into the device. When the edge of the card 1
is detected by the sensor 15, the signals S1 - S3 read as the
information of the card 1 are stored in the memory 12 after a
fixed period of time is elapsed.
Outputs from the magnetic heads MS1 - MS3 are inverted
according to the magnetic polarity, and as shown in Fig. 5,
the combination of S-N-S at the initial edge and the combina-
tion of N-S-N at the final edge are obtained as the truth
determining code.
Then, a desired information (remainder or personal
information, for example) in the memory 12 is read by the
control unit 13, and a proper code is calculated by a
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predetermined operation. Then, the code read at the initial
edge and the final edge is collated with the proper code. If
the code read accords with the proper code, it is determined
that the card 1 is true, and the subsequent operation is
carried out. If the disaccordance between the code read and
the proper code occurs a predetermined times or more, it is
determined that the card 1 has been forged or altered, and the
card 1 is not accepted.
If the card 1 is true, a purchase price, for example,
is inputby auserwith the input unit 14, the remainder is
read by the control unit 13 from the information stored in
the memory 12, and the purchase price is substracted from
the remainder. Then, the difference is stored again in the
memory 12. At this time, when the difference or a fresh
remainder is not more thana fixed amount, for example, the
truth determining code is modified and stored in the memory 12.
For example, the truth determining code is changed into the
combination of S-N-N at the initial edge and the combination
of N-S-S at the final edge.
When the necessary processing is ended, the transfer means
10 is operated by the control unit 13 to reverse the card 1.
At this time, the information in the memory 12 is read by
the control unit 13, and the information including the truth
determining code is written on the tracks Tl - T3 of the card 1
by means of the magnetic heads MS1 - MS3. Then, the card 1
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thus updated is returned to the user.
As described above, the truth determining code is recorded
at the edges of the card 1, indicative of the inversion or
non-inversion of the magnetic polarity. Therefore, even if
the information in the card 1 is merely read by a reader or
the like, the card 1 cannot be forged as far as the system
of the truth determining code is unknown. Thusly, a greatly
high security may be obtained by a simple method.
The above-mentioned embodiments are illustrative and may
be modified or changed within the scope of the present inven-
tion. For example, the present invention is applicable to
the determination of the truth of a general magnetic recording
medium.
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