System for reading encryption / decryption keys and related methods

Abstract

The invention relates to a system for reading encryption / decryption keys and a related method. The present disclosure provides a system and method for reading an encryption / decryption key. One example includes at least one first word including a plurality of bits, the system including a first comparison device, a first delivery device, a second comparison device, and a second delivery device.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to French patent application FR 2310780, filed on October 9, 2023, entitled “Systeme De Lecture D'une Cle DeChiffrement / Dechiffrement Et Procede Associe”, the contents of which are incorporated herein by reference to the maximum extent permitted by law. Technical Field

[0003] Embodiments and implementations relate to reading of encryption / decryption keys stored in a memory, and in particular to secure reading of the keys. Background Art

[0004] Figure 1 An example of a backup system for keys used for, eg, encryption / decryption operations, known in the prior art is schematically shown.

[0005] The backup system includes storage including bits B1, B2, B3, B 127 , B 128 A first memory 1 of an encryption / decryption key 2.

[0006] For example, Key 2 includes 128 bits.

[0007] The system also includes as many multiplexers M1 , M2 , M3 , M127 , M128 as there are bits in Key2 .

[0008] Each multiplexer M1, M2, M3, M127, M128 comprises bits B1, B2, B3, B127 connected to the first memory 1 to read the key 2. 127 , B 128 A first input is connected to a low logic state (eg, a “0” Boolean value) and a second input is connected to a low logic state (eg, a “0” Boolean value).

[0009] Each multiplexer M1 , M2 , M3 , M127 , M128 further comprises a control input connected to the output of the comparator 3 and an output connected to the first register 4 .

[0010] The system also includes a storage device including a series of bits B 11 , B 12 , B 18 The second memory 5 and the storage of the access key 6 include a series of bits B 21 , B 22 , B 28 The second register 7 of word 8.

[0011] For example, when access to the encryption / decryption key 2 is required, the word 8 is delivered via the bus connected to the second register 7 .

[0012] When bit B contained in the second register 7 21 , B 22 , B 28 When the comparator 3 delivers a high logic state at its output, the same as the access key 6, so that each multiplexer M1, M2, M3, M127, M128 delivers at its output bits B1, B2, B3, B127 of the encryption / decryption key 2. 127 , B 128 , the bits delivered by the multiplexers M1 , M2 , M3 , M127 , M128 are stored in the register 4 in order to subsequently use the encryption / decryption key 2 stored in the first register 4 .

[0013] When bit B contained in the second register 7 21 , B 22 , B 28 At least one bit in the same as bit B of access key 6 11 , B 12 , B 18 At the same time, the comparator 3 delivers a low logic state at its output, causing each multiplexer M1, M2, M3, M127, M128 to deliver a bit in the low state "0" at its output, allowing to infer that the word stored in the second register 7 does not enable to read the encryption / decryption key 2. Observation of the outputs of the multiplexers M1, M2, M3, M127, M128 allows to infer that they do not deliver bits of the encryption / decryption key 2.

[0014] Since all multiplexers M1, M2, M3, M127, M128 are controlled by comparator 3, all that is needed is to implement an attack, such as a laser directed on the output of comparator 3 or on a track connecting the output of comparator 3 to multiplexers M1, M2, M3, M127, M128, to force a high logic state on the control inputs of multiplexers M1, M2, M3, M127, M128, so that multiplexers M1, M2, M3, M127, M128 deliver the encryption / decryption key 2 at their outputs.

[0015] Therefore, there is a need to provide a key reading system that is resistant to laser attacks. Summary of the invention

[0016] The implementations and embodiments defined in the following are provided with this in mind and enable the reading system to not deliver encryption / decryption keys during an attack implementing the laser.

[0017] According to one aspect, there is provided a method for reading an encryption / decryption key comprising at least one first word, the first word comprising a plurality of bits, the method comprising:

[0018] a first comparison of a first bit set of an unlocking word comprising a plurality of bits with a first bit set of an access key, the first bit set of the access key comprising at least a first bit of the plurality of bits of the access key,

[0019] delivering at least one first bit set of the first word of the encryption / decryption key, the first bit set being selected from the plurality of bits of the first word, if the first bit set of the unlocking word is identical to the first bit set of the access key,

[0020] at least one second comparison of a second set of bits of the unlock word different from the first set of bits of the unlock word with a second set of bits of the access key, the second set of bits of the access key comprising at least one second bit of the plurality of bits of the access key different from the first bit, and

[0021] If the second bit set of the unlocking word is the same as the second bit set of the access key, at least one second bit set of the first word of the encryption / decryption key is delivered, the second bit set being selected from a plurality of bits of the first word and being different from the bits of the first bit set, the combination of the bit sets of the first word forming the first word.

[0022] In order to obtain the entire encryption / decryption key, two different conditions must be met. The first bit set of the unlock word needs to be the same as the first bit set of the access key to obtain the first part of the key, and the second bit set of the unlock word needs to be the same as the second bit set of the access key to obtain the second part of the key.

[0023] During an attack, two lasers have to be implemented to force the key to be delivered by the first and second delivery means, making the reading system more robust compared to reading systems known in the prior art.

[0024] According to one implementation, the encryption / decryption key includes at least one second word including a plurality of bits, and the method includes:

[0025] delivering at least one first bit set of the second word of the encryption / decryption key when the first bit set of the unlocking word is identical to the first bit set of the access key, the first bit set of the second word being selected from the plurality of bits of the second word, and

[0026] If the second bit set of the unlocking word is the same as the second bit set of the access key, at least one second bit set of a second word of the encryption / decryption key is delivered, the second bit set of the second word is selected from a plurality of bits of the second word and is different from bits of the first bit set of the second word, the combination of the bit sets of the second word forms the second word, and the first and second words form the encryption / decryption key.

[0027] According to one implementation, the bits of at least the bit set of the encryption / decryption key are selected such that the bits do not follow each other.

[0028] According to one implementation, when the set of bits of the unlocking word is not identical to the set of bits of the access key, the method comprises delivering a predetermined set of bits having the same size as the set of bits associated with the comparison.

[0029] According to one implementation, a first bit set of the access key includes a first bit of the access key and a first combination of bits selected from a plurality of bits of the access key, the bits of the first combination being different from the first and second bits of the access key, and a second bit set of the access key includes a second bit and a second combination of bits selected from a plurality of bits of the unlock word, the bits of the second combination being different from the first bit, different from the second bit, and different from the bits of the first combination.

[0030] According to another aspect, there is also provided a system for reading an encryption / decryption key comprising at least one first word, the first word comprising a plurality of bits, the system comprising:

[0031] first comparing means configured to compare a first bit set of an unlocking word comprising a plurality of bits with a first bit set of an access key, the first bit set of the access key comprising at least one first bit of the plurality of bits of the access key,

[0032] first delivery means configured to deliver at least one first bit set of the first word of the encryption / decryption key if the first bit set of the unlocking word is identical to the first bit set of the access key, the first bit set being selected from the plurality of bits of the first word,

[0033] a second comparison device configured to compare a second bit set of the unlock word that is different from the first bit set of the unlock word with a second bit set of the access key, the second bit set of the access key comprising at least one second bit different from the first bit of the plurality of bits of the access key, and

[0034] a second delivery device configured to deliver at least one second bit set of the first word of the encryption / decryption key if the second bit set of the unlock word is identical to the second bit set of the access key, the second bit set being selected from bits of the plurality of bits of the first word that are different from the first bit set, the bit sets of the first word forming the first word in combination.

[0035] According to one embodiment, the encryption / decryption key comprises at least one second word comprising a plurality of bits, the system comprising:

[0036] a third delivery device configured to deliver at least one first bit set of the second word of the encryption / decryption key if the first bit set of the unlock word is identical to the first bit set of the access key, the first bit set being selected from the plurality of bits of the first word, and

[0037] and fourth delivery means configured to deliver at least one second bit set of the second word of the encryption / decryption key if the second bit set of the unlock word is identical to the second bit set of the access key, the second bit set being selected from the plurality of bits of the first word and different from the bits of the first bit set, the plurality of bit sets of the second word forming the first word in combination.

[0038] According to one embodiment, the bits of at least the bit set of the encryption / decryption key are selected such that the bits do not follow each other.

[0039] According to one embodiment, at least one delivery device is configured to deliver a predetermined set of bits having the same size as the set of bits associated with the comparison when the set of bits of the unlocking word associated with the delivery device is not identical to the set of bits of the access key.

[0040] According to one embodiment, a first bit set of the access key includes a first bit of the access key and a first combination of bits selected from a plurality of bits of the access key, the bits of the first combination being different from the first bit and a second bit of the access key, and a second bit set of the access key includes a second bit and a second combination of bits selected from a plurality of bits of the unlock word, the bits of the second combination being different from the first bit, different from the second bit and different from the bits of the first combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Other advantages and features of the present disclosure will become apparent upon review of the detailed description of non-limiting embodiments and implementations and from the accompanying drawings, in which:

[0042] [ Figure 1 ] is a diagram showing a key reading system of the prior art.

[0043] [ Figure 2 ]and[ Figure 3 ] show embodiments and implementations of the present disclosure. DETAILED DESCRIPTION

[0044] Figure 2 A first embodiment of a system for reading an encryption / decryption key 10 is shown.

[0045] For the sake of clarity, it is assumed in this example that the encryption / decryption key 10 comprises a B having eight bits. 31 To B 38 The first word of .

[0046] The first word forms the encryption / decryption key 10 .

[0047] The encryption / decryption key 10 is stored in a first memory 11 connected to a first delivery device 12 and a second delivery device 13 .

[0048] Each delivery device 12 , 13 comprises a first input connected to the first memory 11 , a second input connected to the first register 14 and an output.

[0049] A second input of the first delivery device 12 is connected, for example, to a third storage 15 , and a second input of the second delivery device 13 is connected, for example, to a fourth storage 16 .

[0050] As shown, each delivery device 12,13 includes, for example, a multiplexer including a first input connected to a first input of the delivery device 12,13, a second input connected to a second input of the delivery device 12,13, and an output connected to an output of the delivery device 12,13.

[0051] Alternatively, each delivery device 12, 13 may be made of logic gates.

[0052] The system further comprises a fourth memory 17 which stores a data stream comprising, for example, 8 bits B 41 To B 48 An access key 18, and a second register 19 storing a bit B including the same number of bits as the access key 18 51 To B 58 The unlock word is 20.

[0053] The system further comprises a first comparison device 21 and a second comparison device 22 .

[0054] For example, each comparison device 21, 22 includes a comparator formed by logic gates.

[0055] A first input of each comparing device 21 , 22 is connected to the fourth memory 17 , and a first input of each comparing device 21 , 22 is connected to the second register 19 .

[0056] The output of the first comparison device 21 is connected to a control input of the first delivery device 12 , and the output of the second comparison device 22 is connected to a control input of the second delivery device 13 .

[0057] A method for implementing a first example of a reading system is now described.

[0058] When the unlock word 20 is stored in the second register 19 , the first comparison means 21 compares the first bit set E1 of the unlock word 20 with the first bit set E11 of the access key 18 , and the second comparison means 22 compares the second bit set E2 of the unlock word 20 with the second bit set E12 of the access key 18 .

[0059] The first bit set E1 of the unlocking word 20 includes at least one first bit of the plurality of bits of the unlocking word 20 , and the first bit set E11 of the access key 18 includes at least one first bit of the plurality of bits of the access key 18 .

[0060] The second bit set E2 of unlock word 20 includes at least one second bit of the plurality of bits of unlock word 20 different from the first bit of unlock word 20 , and the second bit set E12 of access key 18 includes at least one second bit of the plurality of bits of access key 18 different from the first bit of access key 18 .

[0061] If the first bit set E1 of the unlocking word 20 is identical to the first bit set E11 of the access key 18 , the first comparison means 21 control the first delivery means 12 so that it delivers the first bit set E21 of the first word of the encryption / decryption key 10 .

[0062] For example, a first set of bits E21 of a delivered first word of the encryption / decryption key 10 is stored in the first register 14 .

[0063] Similarly, if the second set of bits E2 of unlocking word 20 is identical to the second set of bits E12 of access key 18 , second comparison means 22 control second delivery means 13 so that it delivers the second set of bits E22 of the first word of encryption / decryption key 10 .

[0064] For example, the second set of bits E22 of the delivered first word of the encryption / decryption key 10 is stored in the first register 14 .

[0065] The first set of bits E21 of the first word of the encryption / decryption key 10 and the second set of bits E22 of the first word of the encryption / decryption key 10 form the encryption / decryption key 10 .

[0066] Two different conditions must be met in order to obtain the entire encryption / decryption key 10. The first set of bits E1 of the unlocking word 20 must be identical to the first set of bits E11 of the access key 18 to obtain the first part of the key 10, and the second set of bits E2 of the unlocking word 20 must be identical to the second set of bits E12 of the access key 18 to obtain the second part of the key 10.

[0067] During an attack, two lasers must be implemented to force the key 10 to be delivered by the first and second delivery means, making the reading system robust compared to reading systems known in the prior art.

[0068] To further protect the reading system, the first bit set E11 of the access key 18 comprises a first combination of bits selected from the first bit and a plurality of bits of the unlocking word, and the second bit set E12 of the access key 18 comprises a second bit and a second combination of bits selected from a plurality of bits of the unlocking word.

[0069] The second combination of bits is different from the first bit, the second bit and the first combination of bits.

[0070] Furthermore, the bits of the first combination may not follow each other, and the bits of the second combination may not follow each other.

[0071] For example, the first bit set E11 of the access key 18 includes the first bit B 41 , the first combination of bits includes bit B 43 , B 45 , B 47 , the second bit set E12 of the access key 18 includes the second bit B 42 , the first combination of bits includes bit B 44 , B 46 , B 48 .

[0072] In order to further protect the reading system during an attack, when one of the delivery devices 12, 13 is forced to deliver the first bit set E21 of the first word of the encryption / decryption key 10 or the second bit set E22 of the first word of the encryption / decryption key 10, the bits of the first and second sets E21, E22 of bits of the first word of the encryption / decryption key 10 do not follow each other, so that the order of the bits obtained by the attack does not correspond to the order of the bits in the encryption / decryption key 10.

[0073] Of course, alternatively, the bits of one of the first and second sets E21 , E22 of bits of the first word of the encryption / decryption key 10 may not follow each other.

[0074] For example, the first bit set E21 of the first word of the encryption / decryption key 10 includes bits B31 , B 33 , B 35 , B 37 , while the second bit set E22 of the first word of the encryption / decryption key 10 includes bits B 32 , B 34 , B 36 , B 38 .

[0075] When the first bit set E1 of the unlocking word 20 is not identical to the first bit set E11 of the access key 18 , the first comparison means 21 may control the first delivery means 12 such that it delivers a set of predetermined bits stored in the third memory 15 .

[0076] The set of predetermined bits includes the same number of bits as the number of bits contained in the first set E21 of bits of the first word of the encryption / decryption key 10, so that it has the same size as the first set E21. Each bit of the predetermined set of bits is in a high or low logic state, so that when the first set of bits E1 of the unlocking word 20 is different from the first set of bits E11 of the access key 18, the delivered set of predetermined bits looks like a part of the encryption / decryption key 10, thereby misleading a hacker observing the output of the first delivery means 12.

[0077] Similarly, when the second bit set E2 of the unlocking word 20 is not identical to the second bit set E12 of the access key 18, the second comparing means 22 may control the second delivering means 13 so that it delivers a predetermined bit set stored in the fourth memory 16. The delivered predetermined bit set is similar to another part of the encryption / decryption key 10, which misleads a hacker observing the output of the second delivering means 13.

[0078] Of course, the first word may comprise more or less than 8 bits.

[0079] Alternatively, the encryption / decryption key 10 may be composed of a plurality of words.

[0080] Alternatively, the access key may comprise more or less than 8 bits.

[0081] Figure 3 A second embodiment of a system for reading an encryption / decryption key 10 is shown.

[0082] It can be found that the first memory 11 and the first register 14 store 8 bits B 41 To B 48 The fourth memory 17 of the access key 18 and the storage including the bit B 51 To B 58 The second register 19 of the unlock word 20.

[0083] In this embodiment, it is assumed that the encryption / decryption key 10 is formed by a first word 32 and a second word 33. The first word 32 includes, for example, a word denoted as B. 61 To B 92 The second word 33 has 32 bits stored in the first memory 11 and is labeled B. 101 To B 132 32 bits.

[0084] The first and second words 32 , 33 are stored in the first memory 11 .

[0085] The encryption / decryption key 10 comprises 64 bits.

[0086] The reading system comprises a bit B for delivering the first word 32 61 To B 92 The first delivery device set is used to deliver bit B of the second word 33 101 To B 132 A second delivery device set.

[0087] For example, the first delivery device set includes a first delivery device 34 , a second delivery device 35 , a third delivery device 36 , and a fourth delivery device 37 .

[0088] For example, the second delivery device set includes a third delivery device 38 , a fourth delivery device 39 , a first delivery device 40 , and a second delivery device 41 .

[0089] Each delivery device 34,35,36,37,38,39,40,41 comprises a first input connected to the first memory 11, a second input, an output connected to the first register 14 and a control input 34a,35a,36a,37a,38a,39a,40a,41a.

[0090] A second input of the first delivery device 34 of the first delivery device set is connected to the fifth memory 42, a second input of the second delivery device 35 of the first delivery device set is connected to the sixth memory 43, a second input of the third delivery device 36 of the first delivery device set is connected to the seventh memory 44, and a second input of the fourth delivery device 37 of the first delivery device set is connected to the eighth memory 45.

[0091] A second input of the third delivery device 38 of the second delivery device set is connected to a ninth memory 46, a second input of the fourth delivery device 39 of the second delivery device set is connected to a tenth memory 47, a second input of the first delivery device 40 of the second delivery device set is connected to an eleventh memory 48, and a second input of the second delivery device 41 of the second delivery device set is connected to a twelfth memory 49.

[0092] As shown, each delivery device 34, 35, 36, 37, 38, 39, 40, 41 includes, for example, a multiplexer including a first input connected to a first input of the delivery device 34, 35, 36, 37, 38, 39, 40, 41, a second input connected to a second input of the delivery device 34, 35, 36, 37, 38, 39, 40, 41, and an output connected to an output of the delivery device 34, 35, 36, 37, 38, 39, 40, 41.

[0093] The reading system further comprises a first comparing device 50 , a second comparing device 51 , a third comparing device 52 and a fourth comparing device 53 .

[0094] Each comparison device 50 , 51 , 52 , 53 comprises a first input connected to the fourth memory 17 , a second input connected to the second register 19 , and an output.

[0095] The output of the first comparison device 50 is connected to the control input 34a of the first delivery device 34 of the first delivery device set and to the control input 39a of the fourth delivery device 39 of the second delivery device set.

[0096] The output of the second comparison device 51 is connected to the control input 35a of the second delivery device 35 of the first delivery device set and to the control input 38a of the third delivery device 38 of the second delivery device set.

[0097] The output of the third comparison device 52 is connected to the control input 36a of the third delivery device 36 of the first delivery device set and to the control input 41a of the second delivery device 41 of the second delivery device set.

[0098] The output of the fourth comparison device 53 is connected to the control input 37a of the fourth delivery device 37 of the first delivery device set and to the control input 40a of the first delivery device 40 of the second delivery device set.

[0099] A method for implementing a second example of a reading system is now described.

[0100] When the unlock word 20 is stored in the second register 19, the first comparing device 50 compares the first bit set E60 of the unlock word 20 and the first bit set E50 of the access key 18, the second comparing device 51 compares the second bit set E61 of the unlock word 20 and the second bit set E51 of the access key 18, the third comparing device 52 compares the third bit set E62 of the unlock word 20 and the third bit set E52 of the access key 18, and the fourth comparing device 53 compares the fourth bit set E63 of the unlock word 20 and the fourth bit set E53 of the access key 18.

[0101] Each of the first, second, third and fourth sets E50, E51, E52, E53 of bits of the access key 18 comprises at least one bit of a plurality of bits of the access key 18, each bit being different.

[0102] Alternatively, each of the first, second, third and fourth bit sets E50, E51, E52, E53 of the access key 18 includes multiple bits of the access key 18, and the multiple bits of each of the first, second, third and fourth bit sets E50, E51, E52, E53 are different.

[0103] Next, assume that the first bit set E50 of the access key 18 includes bits B 41 , B 42 , B 47 , B 48 , the second bit set E51 of the access key 18 comprises bits B 43 , B 44 , B 45 , B 46 , the third bit set E52 of the access key 18 includes bits B 41 , B 44 , B 45 , B 48 , and the fourth bit set E53 of the access key 18 includes bits B 42 , B 43 , B 46 , B 47 , so that the bits of each set E50, E51, E52, E53 do not follow each other.

[0104] If the first bit set E60 of the unlocking word 20 is identical to the first bit set E50 of the access key 18 , the first comparing device 50 controls the first delivery device 34 of the first delivery device set so that it delivers the first bit set E34 of the first word 32 , and controls the fourth delivery device 39 of the second delivery device set so that it delivers the second bit set E39 of the second word 33 .

[0105] If the second bit set E61 of the unlocking word 20 is identical to the second bit set E51 of the access key 18 , the second comparing device 51 controls the second delivery device 35 of the first delivery device set so that it delivers the second bit set E35 of the first word 32 , and controls the third delivery device 38 of the second delivery device set so that it delivers the first bit set E38 of the second word 33 .

[0106] If the third group of bits E62 of the unlocking word 20 is identical to the third group of bits E52 of the access key 18, the third comparing device 52 controls the third delivery device 36 of the first delivery device set so that it delivers the third bit set E36 of the first word 32, and controls the second delivery device 41 of the second delivery device set so that it delivers the fourth bit set E41 of the second word 33.

[0107] If the fourth bit set E63 of the unlocking word 20 is identical to the fourth bit set E53 of the access key 18, the fourth comparing device 53 controls the fourth delivery device 37 of the first delivery device set so that it delivers the fourth bit set E37 of the first word 32, and controls the first delivery device 40 of the second delivery device set so that it delivers the third bit set E40 of the second word 33.

[0108] The first, second, third and fourth bit sets E34 , E35 , E36 , E37 of the first word 32 form the first word 32 , while the first, second, third and fourth bit sets E38 , E39 , E40 , E41 of the bits of the second word 33 form the second word 33 .

[0109] For example, the bit sets E34 , E35 , E36 , E37 , E38 , E39 , E40 , E41 of the first and second words 32 , 33 delivered by the delivery means are stored in the first register 14 .

[0110] Assume that the first bit set E34 of the first word 32 includes, for example, bits B of the first word 32 61 , B 65 , B 69 , B 73 , B 77 , B 81 , B 85 , B 89 , the second bit set E35 of the first word 32 includes, for example, bits B of the first word 32 62 , B 66 , B 70 , B 74 , B 78 , B 82 , B 86 , B 90 , the third bit set E36 of the first word 32 includes, for example, bits B of the first word 32 63 , B 67 , B 71 , B 75 , B 79 , B 83 , B 87 , B 91 , and the fourth bit set E37 of the first word 32 includes, for example, bits B of the first word 32 64 , B68 , B 72 , B 76 , B 80 , B 84 , B 88 , B 92 .

[0111] Assume that the first bit set E38 of the second word 33 includes, for example, bits B of the second word 33 101 , B 105 , B 109 , B 113 , B 117 , B 121 , B 125 , B 129 , the second bit set E39 of the second word 33 includes, for example, bits B of the second word 33 102 , B 106 , B 110 , B 114 , B 118 , B 122 , B 126 , B 130 , the third bit set E40 of the second word 33 includes, for example, bits B of the second word 33 103 , B 107 , B 111 , B 115 , B 119 , B 123 , B 127 , B 131 , and the fourth bit set E41 of the second word 33 includes, for example, bits B of the second word 33 104 , B 108 , B 112 , B 116 , B 120 , B 124 , B 128 , B 132 .

[0112] The bits of each set E34, E35, E36, E37, E38, E39, E40, E41 of words 32, 33 do not follow each other.

[0113] Of course, alternatively, only the bits of one or more sets E34, E35, E36, E37, E38, E39, E40, E41 of words 32, 33 do not follow each other.

[0114] In order to obtain the entire encryption / decryption key 10, four different conditions must be met.

[0115] The bits of the first bit set E60 of the unlock word 20 must be identical to the bits of the first bit set E50 of the access key 18 to obtain the first bit set E34 of the first word 32 and the second bit set E39 of the second word 33, and the bits of the second bit set E61 of the unlock word 20 must be identical to the bits of the second bit set E51 of the access key 18 to obtain the second bit set E35 of the first word 32 and the first bit set E38 of the second word 33. The bits of the third bit set E62 of the unlock word 20 are identical to the bits of the third bit set E52 of the access key 18 to obtain the third bit set E36 of the first word 32 and the fourth bit set E41 of the second word 33, and the bits of the fourth bit set E63 of the unlock word 20 are identical to the bits of the fourth bit set E53 of the access key 18 to obtain the fourth bit set E37 of the first word 32 and the third bit set E40 of the second word 33.

[0116] During an attack, four lasers need to be implemented to force the delivery device 34, 35, 36, 37, 38, 39, 40, 41 to deliver the key 10, making the reading system more robust compared to reading systems known in the prior art.

[0117] As previously described, each of the memories 42, 43, 44, 45, 46, 47, 48, 49 may contain a series of 8 bits, each bit being similar to a portion of the encryption / decryption key 10, so that when one of the delivery devices 34, 35, 36, 37, 38, 39, 40, 41 is controlled to connect its output to its second input, the delivery device delivers the series of bits contained in the memory connected to the second input.

[0118] Of course, the encryption / decryption key 10 may be formed from more than two words, each word comprising more or less than 32 bits.

Claims

1. A method for reading an encryption / decryption key comprising at least one first word, the first word comprising a plurality of bits, the method comprising: comparing, using a first comparison, a first bit set of an unlock word comprising a plurality of bits with a first bit set of an access key, the first bit set of the access key comprising at least one first bit of the plurality of bits of the access key; delivering at least one first set of bits of the first word of the encryption / decryption key, the first set of bits being selected from the plurality of bits of the first word, if the first set of bits of the unlock word is identical to the first set of bits of the access key; comparing, using at least one second comparison, a second set of bits of the unlock word that is different from the first set of bits of the unlock word with a second set of bits of the access key, the second set of bits of the access key comprising at least one second bit of the plurality of bits of the access key that is different from the first bit; as well as If the second bit set of the unlock word is identical to the second bit set of the access key, at least one second bit set of the first word of the encryption / decryption key is delivered, the second bit set being selected from the plurality of bits of the first word and being different from the bits of the first bit set, the bit sets of the first word being combined to form the first word.

2. The method according to claim 1, wherein the encryption / decryption key comprises at least one second word, wherein the second word comprises a plurality of bits, and the method further comprises: delivering at least one first set of bits of the second word of the encryption / decryption key when the first set of bits of the unlock word is identical to the first set of bits of the access key, the first set of bits of the second word being selected from the plurality of bits of the second word; as well as If the second bit set of the unlock word is identical to the second bit set of the access key, at least one second bit set of the second word of the encryption / decryption key is delivered, the second bit set of the second word being selected from the plurality of bits of the second word and being different from the bits of the first bit set of the second word, the combination of the bit sets of the second word forming the second word, and the first word and the second word forming the encryption / decryption key.

3. The method of claim 1, wherein the bits of at least one bit set of the encryption / decryption key are selected such that the bits do not follow each other. 4 . The method of claim 1 , wherein when the bit set of the unlock word is not identical to the bit set of the access key, the method further comprises delivering a predetermined bit set having the same size as the bit set associated with the comparison.

5. The method of claim 1 , wherein the first bit set of the access key comprises the first bit of the access key and a first combination of bits selected from the plurality of bits of the access key, the bits of the first combination being different from the first bit and the second bit of the access key, and the second bit set of the access key comprises the second bit and a second combination of bits selected from the plurality of bits of the unlock word, the bits of the second combination being different from the first bit, different from the second bit, and different from the bits of the first combination.

6. A system for reading an encryption / decryption key comprising at least one first word, the first word comprising a plurality of bits, the system comprising: a first comparison device configured to compare a first bit set of an unlock word including a plurality of bits with a first bit set of an access key, the first bit set of the access key including at least one first bit of the plurality of bits of the access key; first delivery means configured to deliver at least one first bit set of the first word of the encryption / decryption key if the first bit set of the unlock word is identical to the first bit set of the access key, the first bit set being selected from the plurality of bits of the first word; a second comparison device configured to compare a second bit set of the unlock word different from the first bit set of the unlock word with a second bit set of the access key, the second bit set of the access key comprising at least one second bit of the plurality of bits of the access key different from the first bit; as well as and second delivery means configured to deliver at least one second bit set of the first word of the encryption / decryption key if the second bit set of the unlocking word is identical to the second bit set of the access key, the second bit set being selected from the plurality of bits of the first word and being different from the bits of the first bit set, the bit sets of the first word in combination forming the first word.

7. The system of claim 6, wherein the encryption / decryption key comprises at least one second word, wherein the second word comprises a plurality of bits, and the system further comprises: a third delivery device configured to deliver at least one first bit set of the second word of the encryption / decryption key if the first bit set of the unlocking word is identical to the first bit set of the access key, the first bit set being selected from the plurality of bits of the first word; as well as and fourth delivery means configured to deliver at least one second bit set of the second word of the encryption / decryption key if the second bit set of the unlocking word is identical to the second bit set of the access key, the second bit set being selected from the plurality of bits of the first word and being different from the bits of the first bit set, the bit set of the second word forming the first word in combination.

8. The system according to claim 6, wherein: The bits of at least one bit set of the encryption / decryption key are selected such that the bits do not follow each other.

9. The system according to claim 6, wherein: At least one delivery device is configured to deliver a predetermined set of bits having the same size as the set of bits associated with the comparison when the set of bits of the unlock word associated with the delivery device is not identical to the set of bits of the access key.

10. The system of claim 6, wherein the first bit set of the access key comprises a first combination of the first bit of the access key and bits selected from the plurality of bits of the access key, the bits of the first combination being different from the first bit and the second bit of the access key, and the second bit set of the access key comprises a second combination of the second bit and bits selected from the plurality of bits of the unlock word, the bits of the second combination being different from the first bit, different from the second bit, and different from the bits of the first combination.

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