Abstract:
A system for injecting faults by laser beams into an electronic circuit including: at least two lasers capable of emitting approximately parallel beams; at least one optical system receiving, on the magnifying side, the beams; and a support of the integrated circuit placed on the reducing side of the optical system.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of French patent application number 11/01133, filed on Apr. 13, 2011, entitled DEVICE FOR DISTURBING THE OPERATION OF AN INTEGRATED CIRCUIT, which is hereby incorporated by reference to the maximum extent allowable by law. 
     BACKGROUND 
     1. Technical Field 
     Embodiments generally relate to electronic circuits and, more specifically, to a system for testing or attacking an integrated circuit by optical means. 
     2. Discussion of the Related Art 
     In electronics, security modules (for example, bank chip cards, subscriber identification units, etc.) are circuits containing data which are desired to be kept confidential or, at least, which are desired to have a controlled distribution. Such data, for example, are encryption algorithm keys, authentication or identification codes, etc., or even algorithms implemented for the encryption, the authentication, or the identification. A security module defines an electronic circuit for securely executing applications and guaranteeing the security (secret/integrity) of data manipulated by such applications. 
     Many techniques that may be implemented by hackers or attackers intending to discover the secrets contained in these circuits are known. Among the most current attacks, the attacker attempts to cause an error in the circuit manufacturing, be it to generate a trap in the program executed by the circuit or to force values taken by certain bits. Such attacks known as fault-injection attacks are carried out in multiple ways, for example, by disturbing the circuit power supply, a clock signal, etc. Such attacks may be interpreted in various ways, for example by side channels (by analyzing the power consumption of the electronic circuit when it executes the algorithms, or its electromagnetic radiation, or directly signals provided by the circuit). 
     Among fault injection attacks, embodiments relate to attacks exploiting laser beams disturbing the circuit operation with their rays. Such attacks have become increasingly accurate as the laser beam focusing capacity increases, and presently enable to direct a sufficiently thin and accurate beam onto a logic gate, or even a transistor, to cause its state switching. 
     The very existence of such attack requires for manufacturers to be able to test the resistance of the circuits that they manufacture against such attacks and, regarding laser attacks, the tests amount to implementing the attack on a circuit and making sure that this attack does not enable to discover the secret of the circuit. 
     The bulk of laser devices as compared with the size of the circuit makes it currently difficult to carry out attacks with multiple beams. Now, more and more, buyers and distributors of such circuits require for them to be protected against multiple-beam attacks. 
     There thus is a need for a test bench or attack bench, capable of simultaneously sending several laser beams to different locations of an electronic circuit. 
     SUMMARY 
     An embodiment provides a fault injection attack bench or a bench for testing the resistance of a circuit against such attacks by means of laser beams. 
     Another embodiment provides a system capable of reaching the integrated circuit with laser beams on both surfaces of the circuit. 
     Thus, an embodiment provides a system of fault injection by laser beams in an electronic circuit comprising:
         at least two lasers capable of emitting approximately parallel beams;   at least one optical system receiving, on the magnifying side, said beams; and   a support of the integrated circuit placed on the reducing side of the optical system.       

     According to an embodiment, the optical system is formed of a telescope, the laser beams being applied on the magnifying side of the telescope. 
     According to an embodiment, laser beams are applied to both surfaces of the electronic circuit. 
     An embodiment provides a system for testing the resistance of an electronic circuit against fault injection attacks, comprising an attack system of the above type. 
     The foregoing and other objects, features, and advantages will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified representation of a test or laser beam attack system of the type to which the present invention applies; 
         FIG. 2  is a representation of a usual attack or test system; 
         FIG. 3  is a simplified representation of an embodiment of an attack or test system; 
         FIG. 4  is a simplified representation of another embodiment of an attack or test system; and 
         FIGS. 5A and 5B  are simplified views illustrating an embodiment of the system of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     The same elements have been designated with the same reference numerals in the different drawings, which have been drawn out of scale. For clarity, only those steps and elements which are useful to the understanding of the present disclosure have been shown and will be described. In particular, the internal structure of the integrated circuits submitted to the test or to the attacks which will be described has not been detailed, the present invention being compatible with usual integrated circuits. Further, the lasers used for the implementation of the described embodiments have not been described either, such embodiments being here again compatible with usual lasers. 
       FIG. 1  very schematically shows the elements of a system of laser attack or test against laser beam attacks aiming at injecting faults in an integrated circuit. 
     An electronic circuit or an integrated circuit chip  1  is arranged so that a laser beam f hits integrated circuit  1  on a region which is desired to be attacked or tested. The contacts (not shown) of the integrated circuit are connected (connection  10 ) to a device  15  for exploiting the measurements, typically a microcomputer or a dedicated electronic circuit also used to synchronize the laser. 
     The carrying out of such an attack and the interpretation of the results are usual. A fault injection by the laser beam is caused, focused and directed to a specific location of the chip, and the consequences of this fault injection are examined either by direct analysis of the signals, or by side-channel analysis (consumption, radiation . . . ). 
       FIG. 2  is a simplified representation of a usual installation  2  of attack or test of an integrated circuit by means of a laser. Chip  1  is laid on a support  22  under a microscope  23 . The function of the microscope is to determine the location where laser beam f emitted by a laser  25  must hit the chip. Indeed, the dimensions of an integrated circuit are such that nothing is visible to the naked eye and that the sighting should be performed by means of a microscope. As compared with the size of the integrated circuit, the installation is particularly bulky and, in particular, does not enable an attack of laser beam f with an incidence perpendicular to the integrated circuit surface. 
     Further, with a conventional bench such as illustrated in  FIG. 2 , it is not possible to to simultaneously inject several faults in the integrated circuit by means of several laser beams. In particular, there is not enough room for attacks to be performed with a sufficient accuracy. 
     Another difficulty is to be able to simultaneously perform attacks on both surfaces of the chip. 
     To attack the circuit with several beams, it could have been devised to equip the installation with a mirror system bringing the different beams back towards the circuit. 
       FIG. 3  is a simplified view of an embodiment of a system of attack or test by laser fault injection on an integrated circuit according to this solution. 
     Integrated circuit  1  is still placed on a table  22 ′ which, in this example, comprises an opening  222  under integrated circuit  1  to be attacked or tested. A microscope  23  is used to set, for example, three lasers  25  (L 1 , L 2 , L 3 ). To reach different areas of circuit  1  despite the significant bulk of lasers  25  with respect to the size of circuit  1 , each laser is associated with mirrors  27  and  29  redirecting the beams towards circuit  1 . 
     In the example of  FIG. 3 , an attack on both surfaces of the integrated circuit is assumed. For example, two laser beams L 1  and L 2  are reflected by mirrors  27  towards a concave mirror  29  located above the circuit while a third beam originating from laser L 3  is directed by a mirror assembly  27  towards a concave mirror  29 ′ located under the circuit. 
     The use of concave mirrors enables to redirect the beams and, in a way, to focus them towards the integrated circuit, despite the fact that the lasers are apart from each other, and to keep the use of microscope  23 . 
     Such a solution also enables to attack the circuit on both its surfaces. 
     However, it remains difficult to set, since laser beams do not attack the circuit with an orthogonal direction. 
       FIG. 4  shows a simplified view of a preferred embodiment of a system  4  according to which several laser beams, in the present example originating from two lasers  25  (L 1  and L 2 ), cross a telescope-type optical system  3  (OS) before reaching integrated circuit  1 . The telescope-type optical system is used conversely to a normal use, that is, the laser beams are applied to the telescope lens on the magnifying portion side. As a result, the beams come out tight, but remain parallel to one another to attack circuit  1 . 
     The (reverse) use of a telescope-type optical system also has the advantage that it provides a focusing system enabling a focusing in the beam direction. 
       FIGS. 5A and 5B  are simplified representations of an example of use of one or several systems  4 . 
       FIG. 5A  very schematically shows a table  22 ′ for receiving the circuit to be attacked or to be tested. As in the embodiment of  FIG. 3 , the table comprises an opening  222  under circuit  1  enabling, if need be, an attack from the back side. A microscope-type sighting system  23  is for example used to set the circuit position in directions X and Y (table plane). As a variation, the circuit is randomly scanned to calibrate a first shooting and position X, Y at which the circuit responds is stored. 
     Once the X and Y position has been set, a telescope system  4  of the type of that in  FIG. 4 . To keep the sighting, any usual mechanical setting means may be used. For example, the two devices are supported by a turntable off-centered with respect to the circuit, the respective axes of the devices being on a same circle of the turntable. 
       FIG. 5B  illustrates the position in which system  4  is then placed directly above circuit  1 .  FIG. 5B  also illustrates the reverse use of telescope  3 , showing magnifying lens  31  on the side of lasers  25  and the sighting lens on the side of circuit  1 .  FIG. 5A  also illustrated an optical system equipped, on the side of lens  33 , with an objective enabling a vertical focusing. 
     Finally, a similar system  4 ′ may be provided to attack the other surface (the lower surface in the orientation of the drawings) of circuit  1 . 
     For example, the laser beams provided by lasers  25  are distributed across a diameter on the order of 2 mm at the entrance of telescope  3  to come out gathered within a diameter on the order of one micrometer enabling to disturb the operation of the integrated circuit. 
     Various embodiments have been described, various alterations and modifications will occur to those skilled in the art. In particular, the practical implementation of embodiments and especially the selection of the telescope (for example, with a mirror) is within the abilities of those skilled in the art based on the functional indications given hereabove. In particular, reference has been made to a telescope but the same principle is operative with an optical system of binocular or optical refractor type. 
     Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and the scope of the present invention. Accordingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited only as defined in the following claims and the equivalents thereto.