Security keyboard unit, in particular for the composition of a confidential code.

p0001The invention relates to electronic devices using a keyboard, especially the electronic payment devices, also known as POS terminals, terminals or POS.

p0002These devices are installed in shops, allowing to automate card transactions paiement.Pour regarding the customer may ratify the transaction with his signature or by the composition of their PIN on a small device separated, called customer unit.

p0003Extensive precautions are taken to maintain the confidentiality of this code: - Or it is checked on the spot, by appropriate control means incorporated in the client's case; any transmission of confidential code itself outside the housing customer is then required; - Or this code is checked in a central computer, in which case it leaves the customer housing after undergoing encryption, which makes it virtually indécryptable.

p0004These two functions are now performed by a hybrid integrated circuit, protected resin, part of the customer limping. Of course, the means of control or encryption used by this circuit are kept secret.

p0005Thus, a high security level is achieved.

p0006However, we have found that attackers could try to intercept a confidential code when it passes key to the integrated circuit protected.

p0007More generally, the same risk exists whenever an electronic unit includes a keyboard, connected to means specific to the analysis matrix keyboard by row and column. Indeed, knowledge of the waveform of the keyboard signals analysis allows immediate rise to any confidential information stamped on the keyboard. Simply few connections made on the rows and columns of the matrix keyboard, the information itself can be transmitted for example through a transmission cable that comes with the keyboard unit, or by other means transmisson, including radio. By cons, the signals flowing within the key analysis circuit are relatively complex. This makes it difficult to find use confidential information hit the keyboard. Thus, the term hereinafter generically "protected module" the analysis circuit key, whether or not coated with a resin preventing any physical access to these terminals or input-output connections.

p0008The present invention is primarily intended to improve the safety of a keyboard unit as defined above.

p0009The invention thus applies to a security keypad unit, in particular for composing a confidential code, of the type wherein a housing, provided with an own keyboard matrix analysis by lines and columns, encloses a protected module, for example comprising a microprocessor and memory means, and capable of applying interrogation pulses to each of key lines while scanning the columns of the keyboard, a depressed key producing a specific line-column contacting .

p0010As a very general definition of the invention, the protected module is equipped with bidirectional links towards some at least of the columns and lines of the keyboard, and it comprises means for simulating false actuations of keys, at least some of the interrogation pulses being applied simultaneously to at least one line and at least one column, hindering the possibility of interception PIN spying by the state of the rows and columns of the keyboard.

p0011Indeed, for example, such a false key actuation is indistinguishable from a true key actuation, wherein the interrogation pulse is applied only to a line key, and where we observe that the columns of the keyboard sees transfer the interrogation pulse, due to the establishment of a contact by pressing the key concerned.

p0012According to another aspect of the invention, simulating false actuations of keys is systematic.

p0013In this sense, the protected module applies each of the interrogation pulses to at least one line and at least one column in a variable manner; it performs the real exploration of the keyboard, touch by touch, by scrutinizing every time a row or column called "actually analyzed", which does not receive the interrogation pulse (direct from the protected module).

p0014According to another aspect of the invention, the protected module does not carry out any real interrogation of a selected key during a predetermined time corresponding to the normal operating time of a key, and generates during the same time a false response due to the key selected. Advantageously, the selected button is defined essentially random.

p0015This is a second level of false keystrokes simulation, which makes it even more difficult to intercept PIN spying by the state of rows and columns of the keyboard.

p0016According to another advantageous aspect of the invention, when in the presence of a non-transfer of the start of the interrogation pulse to the analyzed column or line (as defined above), non-transfer that means a non-actuation of one or more keys explored, the protected module responds to this condition by applying to the column or line analyzed a dummy pulse which ends with the interrogation pulse, by its beginning being slightly delayed with respect against at the beginning of the interrogation pulse, given the time necessary decision protected module.

p0017The characteristics of the invention, as defined above, can be applied in different ways. We now consider two embodiments.

p0018In the first, the protected module is equipped with bidirectional links to all the columns of the keyboard. This protected module has a state of pure simulation, where he applies the interrogation pulse to a row and all columns of the keyboard (can thus be simulated different keys corresponding to this line and the various columns); for true exploration of the keyboard, the protected module applies the interrogation pulse to a row and all columns except to analyze the key actually explored defined by the interrogated line and analyzed column. Of course, in case of no response will employ the dummy pulse as defined above.

p0019Similarly, during a time corresponding to the time of normal operation of a key, the module protected s'abstient of any interrogation of a key chosen at the same time it produces a state of pure simulation applicable to the key, which fixed the rank of the corresponding line.

p0020In practice, the keys are actually explored and are not processed in the order. It may be interesting to define the keys actually explored essentially random. The word "substantially" here refers firstly to the fact that a random perfectly random fate is difficult to obtain data on the other hand the fact that there should be excluded the simulated key, and, preferably keys interviewed recently.

p0021Another installment in the random character of the exploration of the keyboard can be brought in a particular embodiment, that the protected module applies the interrogation pulse cyclically to the different lines; in these conditions, only the column which does not receive the interrogation pulse is determined substantially randomly.

p0022Now we will look at the second embodiment of the invention. Functionally, it differs from the first in that the analysis of a key will now re off Product sequentially, first determining the row and the column to which belongs the key or vice versa.

p0023In this case, the protected module is equipped with bidirectional links both for the lines to the columns of the keyboard; in his state of pure simulation, protected module applies the pulse simultaneously query to all the rows and columns of the keyboard (the simulated key is then defined simply by the fact that we will refrain from any real interrogation in respect for the predetermined time); for the true exploration, the protected module applies the interrogation pulse the one hand to all the lines and columns except for one analyzed line, on the other hand to all the lines and columns except for one analyzed column, the key actually being explored defined by the line and the analyzed column.

p0024Arrangements can be made to the second embodiment defined in the sense that we can analyze the first column and the line. If one has set a button to analyze, and the line connecting this key does not respond, it can of course refrain from analyzing the column. Other variations will occur to those of skill in the art, given the random characteristics of the analysis, we considered hereafter.

p0025Indeed, in general, it is advantageous that the key actually explored is defined essentially random (with the same caveats as above on the simulated key, and avoidance of a new exploration of recently explored keys).

p0026Also, the rows and columns can be analyzed alternately or in a more haphazard, ensuring of course that we can analyze all the keyboard keys within a reasonably short period of time.

p0027The present invention can also be expressed as a method to obstruct the interception of information struck on a keyboard, to a data processing module. According to this method, simulating false actuations of keys simultaneously applying the same interrogation signal to at least one line and at least one column of the analysis matrix of the keyboard, while a real key exploration is performed, touch by touch, using every time a row or column receiving the interrogation signal and, respectively, a column or row actually analyzed, which does not receive the interrogation pulse. Pressing the key product explored the transfer of the interrogation signal over the analysis column or row, whose state is indistinguishable from those corresponding to the wrong keystrokes.

p0028Other features and advantages of the invention appear on reading the detailed description below and the appended drawings, in which:<ul><li>- Figure 1 is a perspective view showing a transaction terminal connected via a cable to a confidential code composition unit or "customer housing";</li><li>- Figure 2 is the electrical circuit diagram of the circuits contained within the customer housing;</li><li>- Figure 3 is a block diagram of a 16-key keypad;</li><li>- Figure 4 is a timing diagram recalling the conventional operation of a key according to Figure 3;</li><li>- Figure 5 is a timing diagram showing the operation of the device according to the first embodiment of the invention; </li><li>- Figure 5A is a schematic diagram of various operations to be performed at the protected module for the operation of FIG 5;</li><li>- Figure 6 is a timing diagram showing the operation of the device according to the invention, in the second embodiment; and</li><li>- Figure 6A is a schematic diagram of the module operations protected for the operation illustrated in Figure 6.</li></ul>

p0029The accompanying drawings comprise many elements of certain character. Accordingly, they are incorporated in the description not only to better understand it but also to serve the definition of the invention, if any.

p0030Furthermore, in the detailed description below, we will only consider the case of a banking transaction terminal, it being observed that the application of the invention can be more general.

p0031In Figure 1, the reference TCO refers to a transaction terminal, which can be an electronic payment terminal (E200 series sold by the Applicant) or a multi-cashing shops terminal (E300 series also sold by the Applicant) .

p0032This terminal is connected by a DC connection cable to a customer BCL housing, the housing 6 itself is topped by a 30 shelter, clean to hide from prying eyes a keyboard 2 and a display 3.

p0033In the circuit diagram of Figure 2, there are 6 in the outer boundaries of the housing. The protected module 1 which is a hybrid integrated circuit includes a clock 10 connected to a microprocessor 12. The address bus BA1 thereof through control logic 14 to come into Ba2 to a dead memory 16 (MEM or ROM) and a random access memory 18 (RAM or RAM).

p0034CC connection cable is the only electrical connection that passes through the wall 6 of the housing. It includes eg a DCC power connection, a ground connection GMB, a saved or rescued supply voltage denoted Vsec. This serves to supply the RAM 18, which contains the own secret data either in situ control of the confidential code or encryption thereof for remote transmission, in a position where it can be PIN control.

p0035The protected module further includes a data bus BD, for trade with the memories 16 and 18, and a program application link PGM, to the ROM 16.

p0036As required, other connections can go through the DC cable, ie signals EX1, EX2, (exchange commands between the microprocessor and TCO BCL bodies), R &amp; D and ED signals (direction control binding series) and the VPP signal.

p0037The electrical connections between the keyboard 2 and the protected module 1, which do not pass through a standard interface, include, matrix form connections called "lines" and called bonds "columns".

p0038Figure 3 illustrates a particular embodiment of the 16-key keypad illustrated at 2 in figure 1. We can distinguish the lines a to d and columns 1 through 4. Of course, the roles of rows and columns is conventional, and can be reversed.

p0039Figure 3 also shows the correspondence between each pair of row and column information and each of the keyboard. One can define four function keys F1 to F4, ten number keys 0-9, a clear key C, and a key point V.

p0040Figure 4 illustrates the classic analysis of a keyboard of this type. Periodic interrogation pulses are applied sequentially and in a manner offset to the lines a to d. Examining each time the response of columns 1 to 4. In the example shown, this is the column 3 which responds in synchronism with the application of the interrogation pulse on line B. It is therefore B3 key (figure 5) which is actuated. The explanation is this: when pressing the 5 key, contact is made between the line and column B 3. The interrogation pulse applied to line B is then transferred to column 3. This allows the module protected from what is the key pressed. Subsequently, we systematically cross hatch marks an interrogation pulse and transferred between a line and a column (or vice versa).

p0041The man in the art it is very easy, by plugging son in parallel to the rows and columns of the keyboard, and recording the signals that are there present, to find the code typed on the keyboard.

p0042It is of course possible to reduce physical access to routes between the protected module and the keyboard. Nevertheless, as short and very accessible they are, these bonds can still be subject to visants connections to espionage keyboard.

p0043Once the connection has been made, the information gathered can be transmitted remotely or through the transmission cable DC or by any other means, including radio transmission means.

p0044The present invention aims to make it extremely difficult to use signals collected on the rows and columns of the keyboard in order to find the PIN, unless you have an extremely complex and advanced equipment.

p0045We will now describe the first embodiment of the invention with reference to Figures 5 and 5A.

p0046In Figure 5, it appears that the lines a to d key is queried sequentially, in the same manner as in Figure 4. This query can be done directly, from the microprocessor 12, or through a decoder .

p0047For their part, the connections that range from 12 to microprocessor keyboard columns are bidirectional links, so that can not only detect whether the interrogation pulse "line" is transferred by pressing a key, to the one of the key columns, but also applied directly from the microprocessor 12 the interrogation pulse to at least some of the columns of the keyboard.

p0048The real key exploration occurs as follows:

p0049During the first pulse on the line, the columns 1, 3 and 4 also receive the interrogation pulse.

p0050By against the column 2 does not receive it. The microprocessor 12 concludes that the scanned key (a2) is not actuated. It then immediately applied on this column 2 a dummy pulse (marked by simple hatching), which is going to start a little after normal interrogation pulses, and end with them. The advantage of such a dummy pulse is after a remote transmission of signals, it will become very difficult to distinguish the interrogation pulses themselves.

p0051For pulses following question, things are going the same way, but it changes each time the button explored, allowing to determine the state of the keyboard keys b3, c1, d1, a3, b4 and c4 successively.

p0052Of course, the scanning rate by the interrogation pulse is chosen to be sufficiently high that there is no risk of missing the actuation of a key by the operator, which typically takes a time of 0, 1 to 0.5 seconds, following operator training.

p0053After the control button c4, the microprocessor 12 performs a pure simulation of applying the interrogation pulse simultaneously to the line and each column 1-4. This may suggest a scam that a key d1 to d4 has been pressed. Such simulation is repeated for a time equal or slightly lower than the normal actuation of a key (for example 0.1 to 0.5 seconds). This time may be predetermined or adjusted by the microprocessor based on data such as the operator's typing speed opposite which it is located.

p0054During the same time, the microprocessor 12 refrains from any questioning of a button selected, eg d2 key, so that the fraudster is led to believe that the d2 button is actually pressed. 5 shows that after a cut, which precisely corresponds to the predetermined time as defined. Then, the example is carried out analyzing b2 key, which does not respond (where a dummy pulse) to a simulation on one of the keys cx (x here designating one of the columns 1 to 4) and to the analysis of other keys d2, a1, b3, c2, d1.

p0055After that, a real actuator is illustrated the key a4. The microproceseur 12 applied the interrogation pulse in the line, and columns 1 to 3. But the interrogation pulse also appears on column 4, due to the depression of the key a4. If necessary, after little reiterate control a4 key.

p0056In any case, the process continues with the analysis of keys b2, c4, then d3, a new control on the a4 key that is really actuated and b3, and so on.

p0057Thus is performed a simulation of fake keystrokes, at two levels: - When a false actuation of buttons, wherein all the columns receive the interrogation pulse (dx case) is obtained on the rows and columns of the keyboard indistinguishable states of a true key operation (a4 case) - By failing to explore a key selected, for example raffled (naturally avoiding actually touch during actuation), we believe that a fraudster that it is the selected button is pressed, which n ' is not.

p0058In addition, to access this information, the hacker must first be able to identify all pulses dummy, which is very delicate, because it should then detect error signals shifts of a few microseconds, and that at the end of a cable 2 at least 3 meters.

p0059Even if it happens and to identify all the false codes corresponding to simulated real keys and codes corresponding to actual keys pressed, the fraudster will increasingly limit registration of the data to the actual strike period PIN, and then try different codes possible, given the mix of real keystrokes and simulated keystrokes.

p0060It is then relatively easy to generate sufficient simulated key for the number of possible codes that must try the fraudster exceeds the number of errors that tolerate credit cards.

p0061It is advantageous to randomize (where possible) all the processes followed by the microprocessor.

p0062In this embodiment, the sequence of application of the interrogation pulse the keypad lines remains fixed and periodic as in the prior art. It is of course done differently.

p0063By cons, can be made substantially random: - The choice, every time, the column that we will not apply the interrogation pulse. We exclude of course the draw the "simulated". It may also be desirable to avoid questioning again already recently explored key. - The production of the simulation, that is to say the instants of simultaneous application of the interrogation pulse to one of the lines and all columns.

p00645A illustrates, for example, a sequence of operations achievable by the microprocessor 12 for implementing the first embodiment of the invention.

p0065Step 50 is to decide what is the key that we will simulate here the d2 button.

p0066Step 51 consists in sending the interrogation pulse to one of the lines a, b, c, d, for example cyclic manner described.

p0067Step 52 then determines if one is interrogating the d line (which is the key to simulate) and whether it is time to perform a simulation. This time can be determined by a draw and the use of a timer.

p0068If so, step 53 is to send the interrogation pulse (present on the d-line) on all columns 1, 2, 3, 4.

p0069Otherwise, step 54 consists in choosing a key to explore on the current line, excluding the simulated key, and optionally the recently explored keys.

p0070Step 55 then determines that it also sends the interrogation pulse to all the columns, except the button to explore (in practice, this is step 55 will determine the transmission of the pulse question simultaneously to the row and all columns except one).

p0071The step 56 is to determine if the beginning of the interrogation pulse is present on the column of the key to explore. The answer yes means that the interrogation pulse has been transmitted from the line in the column, and therefore that explored the key is actually pressed. The valid step 57 then explored the actuation button.

p0072Otherwise, step 58 involves applying a dummy pulse on the scanned key column.

p0073The outputs of the stages 53, 57 and 58 meet at the input of a test 59 determines if the time delay of the simulation is over. If this condition is not satisfied, return to step 51. Otherwise, it returns to step 50, to decide on a new touch to simulate.

p0074The functions of Figure 5A are easily achievable using an internal microprocessor to maintain several meters long, to generate random quantities (or rather pseudo-random) and provided with a suitable interface for the production of electrical pulses at the required rate.

p00756 illustrates the second embodiment of the invention.

p0076It differs from the first previous in that all connections between the microprocessor 12 and the keyboard are bidirectional. We can then apply the interrogation pulse indifferently to rows and columns, and, likewise, the scan transfer of the interrogation pulse on any row or column.

p0077The advantage is that one then significantly increase the number of possible combinations.

p0078In return, the exploration of a key will be in two stages, first by the line, then by the column to which it belongs, or vice versa. We must therefore generate more interrogation signal sequences at the same time, in order not to lose information about the real state of the keyboard.

p0079In Figure 6, first it is observed that the interrogation pulse is applied to all the lines a to d and the columns 1, 3 and 4. Nothing appears on the column 2, the microprocessor 12 immediately applies a dummy pulse.

p0080Then he did the same successively with line, line b, column 4. In all cases, nothing happens and a dummy pulse is applied.

p0081Immediately after, the microprocessor produces a pure simulation condition as before. The difference however is that the interrogation pulse is now applied to all rows and columns.

p0082A moment later, it is again the column 2 which is explored.

p0083Assume that, so far, the microprocessor had chosen to simulate a fake pressing the button b2, by thus refraining from any question likely to match this key. The fraudster will thus naturally tend to allocate the state of pure simulation (denoted x) to the b2 button. As before, this occurs for a predetermined time, possibly adjusted by the microprocessor.

p0084After the first cut of Figure 6, there is a state of pure simulation, noted there and exploring the line, column 2.

p0085Then we are in the presence of a real actuation of the line b.

p0086After the interruption following in the representation of the signals, we find again a pressing one of the buttons corresponding to the line b.

p0087Then the question of Column 3 does not work, hence producing a dummy pulse.

p0088After that, we get a real operation to one of the buttons of the column 4, a condition which manifests itself again after the last break in the representation of the signals presented in Figure 6.

p0089Provided the answers on the line b and column 4 are sufficiently close in time, the microprocessor deduced that the b4 key has been pressed by the user.

p0090Against by the fraudster n'est not able to differentiate between the conditions under which the interrogation pulse is present on all the lines and columns following actuation of this button b4, on the one hand, and the conditions under which the interrogation pulse is present on all the lines and columns of the result of a state of pure simulation in the microprocessor, on the other hand.

p0091In addition, and as previously, the "non-examination" of a simulated key will tend to believe that a fraudster key has been pressed.

p0092With this second embodiment, the difficulties that meet the fraudster to truly access the PIN are in principle the same as before. But his task is made even more complex because of the decomposition in two stages of exploration of the keys. Note also that the fraudster no longer has any information about the state of pure simulation, whereas previously he knew the line he was.

p0093Of course, we can make random as before determining the line or column to which the interrogation pulse is not applied, avoiding of course the simulated key, and possibly too close questions likely to correspond to the same touch.

p0094Can also be made random times which are products of pure simulation states, and determination of the simulated key, we will refrain from exploring to believe that she is truly pressed.

p0095The second embodiment of the invention can be implemented by executing by the microprocessor 12 the following operations illustrated in Figure 6A.

p0096The first operation 60 is a decision the key to simulate here the b2 button.

p0097The test 61 determines whether it is time to perform the simulation. If yes, step 62 sends the interrogation pulse to all rows and all columns.

p0098Otherwise, step 63 consists in choosing a key to truly explore, excluding of course the simulated key, and if desired the recently explored keys (unsuccessfully).

p0099Step 64 then involves sending the interrogation pulse to all rows and columns except the row (or column) of the key to explore.

p0100Step 65 determines whether the beginning of the interrogation pulse is present on the line (or column) in question. If it is not, step 66 applies a dummy pulse on line and / or column.

p0101If on the contrary the interrogation pulse is present, the step 67 consists in storing the row (or column) in question.

p0102After step 67, proceed to step 68. The output of step 66 could also be a passage through step 68, or simply a direct jump to Step 72.

p0103Step 68 involves sending the interrogation pulse to all rows and columns except the column (or row) of the key to explore.

p010469 the test is to determine if the beginning of the interrogation pulse is present on the column (or row) in question. Otherwise, step 70 is to apply the dummy pulse on the column (or row) in question.

p0105If so, step 71 is to validate the operation of the key defined by the row and column in question, given the information stored in 67.

p0106The illustration given in Figure 6A, as the above explanation, maintains the symmetry between the line and the column being observed that must always have an information line and column information to determine the actuation of a key. However, the order in which information is both indifferent is obtained. In addition, as illustrated in Figure 6, it is not necessary that one has systematically an alternation between rows and columns. This can however be interesting to simplify the work of the microprocessor 12.

p0107The outputs of the stages 62, 66, 70 and 71 go to a test 72 determines if the simulation time delay has elapsed.

p0108If it is not, it returns to step 61. If, against this timer expires, we go back up to step 60, to decide on a new touch to simulate.

p0109As before, it is estimated that the microprocessor 12 can easily perform the functions of Figure 6A with stopwatches and clocks a suitable interface for the production and analysis of interrogation pulses.

p0110Consider now indifferently both embodiments of the invention.

p0111Of course, it is necessary that the interrogation pulse rate is sufficient to allow a full interrogation of all the keys, given the random component above, in a time that corresponds to the time normally taken by an operator to strike their PIN.

p0112It is clear that the present invention provides a particularly interesting solution to preserve the confidentiality of information typed on a keyboard, and in particular a PIN bank card.

p0113With the means described, it becomes actually possible to simplify significantly, if not eliminate, the other physical protections that could be considered further.

p0114The man in the art can design different variants of the described embodiments. Of course, the present invention extends to all such variations as far as they are covered by the following claims.