System for reading an encryption / decryption key and associated process
A dual-comparison and dual-delivery mechanism for encryption/decryption keys, requiring multiple laser attacks and misdirection, secures the key reading system against unauthorized access.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- STMICROELECTRONICS INT NV
- Filing Date
- 2023-10-09
- Publication Date
- 2026-06-12
AI Technical Summary
Existing encryption/decryption key reading systems are vulnerable to attacks using lasers, allowing unauthorized access to the encryption/decryption key.
Implement a dual-comparison and dual-delivery mechanism where two different sets of bits from an unlock word must match the corresponding sets of bits in an access key to deliver parts of the encryption/decryption key, and additional measures to mislead attackers during forced delivery.
Enhances the robustness of the key reading system by requiring multiple laser attacks and misdirection during unauthorized access, making it more secure than prior art systems.
Smart Images
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Abstract
Description
Title of the invention: System for reading an encryption / decryption key and associated method
[0001] Some embodiments and implementations relate to reading an encryption / decryption key stored in memory, in particular securing the reading of said key.
[0002] Fig. 1 schematically illustrates an example of a key backup system used for example for encryption / decryption operations as known from the prior art.
[0003] The backup system includes a first memory 1 storing an encryption / decryption key 2 comprising bits Bh B2, B3, Bi27, Bi28.
[0004] Key 2, for example, comprises one hundred and twenty-eight bits.
[0005] The system also includes as many multiplexers M1, M2, M3, M127, M128 as there are bits in key 2.
[0006] Each multiplexer M1, M2, M3, M127, M128 includes a first input connected to the first memory 1 to read a bit Bb B2, B3, Bi27, Bi28 of the key 2 and a second input connected to a low logic state, for example a boolean "0".
[0007] Each multiplexer M1, M2, M3, M127, M128 further includes a control input connected to an output of a comparator 3 and an output connected to a first register 4.
[0008] The system further comprises a second memory 5 storing an access key 6 comprising a sequence of bits Bu, Bi2, Bi8 and a second register 7 storing a word 8 comprising a sequence of bits B2[, B22, B28.
[0009] Word 8 is for example delivered by a bus connected to the second register 7 when access to the encryption / decryption key 2 is required.
[0010] When the bits B2[, B22, B28 contained in the second register 7 are identical to the access key 6, the comparator 3 delivers a logic high state on its output so that each multiplexer M1, M2, M3, M127, M128 delivers on its output a bit Bb B2, B3, B27, B[28 of the encryption / decryption key 2, the bits delivered by the multiplexers M1, M2, M3, M127, M128 being stored in the register 4 for later use of the encryption / decryption key 2 stored in the first register 4.
[0011] When at least one of the bits B2b, B22, B28 contained in the second register 7 is different from the bits Bu, Bi2, Bi8 of the access key 6, the comparator 3 outputs a logic low state on its output so that each multiplexer M1, M2, M3, M127, M128 outputs a bit in the low state "0" allowing it to be deduced that the stored word in the second register 7 does not allow the reading of the encryption / decryption key 2. Observation of the output of the multiplexers M1, M2, M3, M127, M128 allows us to deduce that they do not deliver bits of the encryption / decryption key 2.
[0012] Since the set of multiplexers M1, M2, M3, M127, M128 are controlled by comparator 3, it is sufficient to carry out an attack implementing, for example, a laser directed at the output of comparator 3 or at a track linking the output of comparator 3 to the multiplexers M1, M2, M3, M127, M128 to force a logic high state at the control input of the multiplexers M1, M2, M3, M127, M128 so that the multiplexers M1, M2, M3, M127, M128 deliver the encryption / decryption key 2 on their output.
[0013] Thus, there is a need to provide key reading systems that are resistant to attacks using a laser.
[0014] The implementation and embodiment methods defined below are proposed in these respects, and allow a reading system not to deliver the encryption / decryption key during an attack using a laser.
[0015] According to one aspect, a method for reading an encryption / decryption key comprising at least a first word comprising a plurality of bits is proposed, the method comprising:
[0016] - a first comparison of a first set of bits of an unlock word comprising a plurality of bits and a first set of bits of an access key, the first set of bits of the access key comprising at least one first bit of the plurality of bits of the access key,
[0017] - a delivery of at least a first set of bits from the first word of the key of encryption / decryption if the first set of bits in the unlock word is identical to the first set of bits in the access key, the first set of bits being chosen from the plurality of bits in the first word,
[0018] - at least a second comparison of a second set of bits of the die word different locking of the first set of bits of the unlock word and a second set of bits of the access key, the second set of bits of the access key having at least one second bit of the plurality of bits of the access key different from the first bit, and
[0019] - the delivery of at least a second set of bits from the first key word of encryption / decryption if the second set of bits of the unlock word is identical to the second set of bits of the access key, the second set of bits being chosen from the plurality of bits of the first word and different from the bits of the first set of bits, the union of the sets of bits of the first word forming the first word.
[0020] To obtain the complete encryption / decryption key, two different conditions must be met. The first set of bits in the unlock word must be identical to the first set of bits in the access key to obtain the first part of the key, and the second set of bits in the unlock word must be identical to the second set of bits in the access key to obtain the second part of the key.
[0021] During an attack, it is necessary to implement two lasers to force the delivery of the key by the first and second delivery means, thus making the reading system more robust compared to a known prior art reading system.
[0022] According to one embodiment, the encryption / decryption key comprises at least one second word comprising a plurality of bits, the method comprises:
[0023] - a delivery of at least a first set of bits of the second key word of encryption / decryption 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 chosen from the plurality of bits of the second word, and
[0024] - the delivery of at least a second set of bits from the second key word of encryption / decryption if the second set of bits of the unlock word is identical to the second set of bits of the access key, the second set of bits of the second word being chosen from the plurality of bits of the second word and different from the bits of the first set of bits of the second word, the union of the sets of bits of the second word forming the second word and the first and second words forming the encryption / decryption key.
[0025] According to one embodiment, the bits of at least one set of bits of the encryption / decryption key are chosen so that said bits do not follow one another.
[0026] According to one embodiment, when a set of bits of the unlock word is not identical to a set of bits of the access key, the method includes issuing a set of predetermined bits having the same size as the set of bits associated with said comparison.
[0027] According to one embodiment, the first set of bits of the access key comprises the first bit of the access key and a first combination of bits chosen from the 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 the second set of bits of the access key comprises the second bit and a second combination of bits chosen from the plurality of bits of the unlock word, the bits of the second combination being different from the first bit, the second bit and the bits of the first combination.
[0028] According to another aspect, a system for reading an encryption / decryption key comprising at least a first word comprising a plurality of bits is also proposed, the system comprising:
[0029] - a first comparison means configured to compare a first set of a bit from an unlock word comprising a plurality of bits and a first set of bits from an access key, the first set of bits from the access key comprising at least one first bit from the plurality of bits of the access key,
[0030] - a first delivery means configured to deliver at least a first set of bits from the first word of the encryption / decryption key if 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 being chosen from the plurality of bits of the first word,
[0031] - a second comparison means configured to compare a second a set of bits in the unlock word that differs from the first set of bits in the unlock word and a second set of bits in the access key, the second set of bits in the access key having at least one second bit from the plurality of bits in the access key that differs from the first bit, and
[0032] - a second delivery means configured to deliver at least a second set of bits of the first word of the encryption / decryption key if the second set of bits of the unlock word is identical to the second set of bits of the access key, the second set of bits being chosen from the plurality of bits of the first word and different from the bits of the first set of bits, the union of the sets of bits of the first word forming the first word.
[0033] According to one embodiment, the encryption / decryption key comprises at least one second word comprising a plurality of bits, the system comprising:
[0034] - a third delivery means configured to deliver at least a first set of bits from the second word of the encryption / decryption key if the first set of bits from the unlock word is identical to the first set of bits from the access key, the first set of bits being chosen from the plurality of bits in the first word, and
[0035] - a fourth delivery means configured to deliver at least a second set of bits of the second word of the encryption / decryption key if the second set of bits of the unlock word is identical to the second set of bits of the access key, the second set of bits being chosen from the plurality of bits of the first word and different from the bits of the first set of bits, the union of the sets of bits of the second word forming the first word.
[0036] According to one embodiment, the bits of at least one set of bits of the encryption / decryption key are chosen so that said bits do not follow one another.
[0037] According to one embodiment, at least one delivery means is configured to deliver a predetermined set of bits when the bit set of the unlock word associated with said delivery means is not identical to a bit set of the access key, the predetermined bit set having the same size as the bit set associated with said comparison.
[0038] According to one embodiment, the first set of bits of the access key comprises the first bit of the access key and a first combination of bits chosen from the 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 the second set of bits of the access key comprises the second bit and a second combination of bits chosen from the plurality of bits of the unlock word, the bits of the second combination being different from the first bit, the second bit and the bits of the first combination.
[0039] Other advantages and features of the invention will become apparent upon examination of the detailed description of embodiments and implementations, which are by no means limiting, and the accompanying drawings in which:
[0040] [Fig-1] illustrates a key reading system according to the prior art, and
[0041] [Fig.2] ;
[0042] [Fig.3] ;
[0043] illustrate embodiments and implementations of the invention.
[0044] Fig. 2 illustrates a first example of the realization of a system for reading an encryption / decryption key 10.
[0045] For the sake of clarity, it is assumed in this example that the encryption / decryption key 10 has a first word of eight bits BM to B38.
[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 means 12 and to a second delivery means 13.
[0048] Each delivery means 12, 13 includes a first input connected to the first memory 11, a second input and an output connected to a first register 14.
[0049] The second input of the first delivery means 12 is for example connected to a third memory 15 and the second input of the second delivery means 13 is for example connected to a fourth memory 16.
[0050] As shown, each delivery means 12, 13 includes for example a multiplexer having a first input connected to the first input of the delivery means 12, 13, a second input connected to the second input of the delivery means 12, 13, and an output connected to the output of the delivery means 12, 13.
[0051] Alternatively, each delivery means 12, 13 can be implemented from logic gates.
[0052] The system further includes a fourth memory 17 storing an access key 18 comprising, for example, eight bits B4i to B48, a second register 19 storing an unlock word 20 comprising the same number of bits B5i to B58 as the access key 18.
[0053] The system further comprises a first means of comparison 21 and a second means of comparison 22.
[0054] Each comparison means 21, 22 includes, for example, a comparator made from logic gates.
[0055] A first input of each comparison means 21, 22 is connected to the fourth memory 17 and a first input of each comparison means 21, 22 is connected to the second register 19.
[0056] An output of the first comparator means 21 is connected to a control input of the first delivery means 12 and an output of the second comparator means 22 is connected to a control input of the second delivery means 13.
[0057] Now, a method for implementing the first example of the reading system is described.
[0058] When the unlock word 20 is stored in the second register 19, the first comparison means 21 compares a first set El of bits of the unlock word 20 and a first set El 1 of bits of the access key 18, and the second comparison means 22 compares a second set E2 of bits of the unlock word 20 and a second set E12 of bits of the access key 18.
[0059] The first set El of bits of the unlock word 20 includes at least one first bit of the plurality of bits of the unlock word 20 and the first set El 1 of bits of the access key 18 includes at least one first bit of the plurality of bits of the access key 18.
[0060] The second set E2 of bits of the unlock word 20 includes at least one second bit of the plurality of bits of the unlock word 20 different from the first bit of the unlock word 20 and the second set E12 of bits of the access key 18 includes at least one second bit of the plurality of bits of the access key 18 different from the first bit of the access key 18.
[0061] If the first set of bits El of the unlock word 20 is identical to the first set El 1 of bits of the access key 18, the first comparison means 21 drives the first delivery means 12 so that it delivers a first set E21 of bits of the first word of the encryption / decryption key 10.
[0062] The first set E21 of bits of the first word of the encryption / decryption key 10 delivered is for example stored in the first register 14.
[0063] Similarly, if the second bit set E2 of the unlock word 20 is identical to the second bit set E12 of the access key 18, the second comparison means 22 drives the second issuance means 13 so that it delivers a second set E22 of bits from the first word of the encryption / decryption key 10.
[0064] The second set E22 of bits of the first word of the encryption / decryption key 10 delivered is for example stored in the first register 14.
[0065] The first set E21 of bits of the first word of the encryption / decryption key 10 and the second set E22 of bits of the first word of the encryption / decryption key 10 form the encryption / decryption key 10.
[0066] To obtain the entire encryption / decryption key 10, two different conditions must be met. The first set of bits El of the unlock word 20 must be identical to the first set El1 of bits of the access key 18 to obtain the first part of the key 10, and the second set of bits E2 of the unlock word 20 must be identical to the second set E12 of bits of the access key 18 to obtain the second part of the key 10.
[0067] During an attack, it is necessary to implement two lasers to force the delivery of the key 10 by the first and second delivery means, thus making the reading system more robust compared to a known prior art reading system.
[0068] In order to further secure the reading system, the first set El 1 of bits of the access key 18 includes the first bit and a first combination of bits chosen from the plurality of bits of the unlock word, and the second set E12 of bits of the access key 18 includes the second bit and a second combination of bits chosen from the plurality of bits of the unlock word.
[0069] The bits of the second combination are different from the first bit, the second bit and the bits of the first combination.
[0070] Furthermore, the bits of the first combination may not be consecutive and the bits of the second combination may not be consecutive.
[0071] For example, the first set El 1 of bits of access key 18 includes the The first bit B4i and the first combination of bits comprise bits B43, B45, B47, and the second set E12 of bits of the access key 18 comprises the second bit B42 and the first combination of bits comprises bits B44, B46, B48.
[0072] In order to further secure the reading system during an attack when one of the delivery means 12, 13 is forced to deliver the first set E21 of bits of the first word of the encryption / decryption key 10 or the second set E22 of bits 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 are not consecutive so that the order of the bits obtained by the attack does not correspond to the order of said bits in the encryption / decryption key 10.
[0073] Of course, alternatively, only 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 be consecutive.
[0074] For example, the first set E21 of bits of the first word of the encryption / decryption key 10 includes bits B3b, B33, B35, B37, and the second set E22 of bits of the first word of the encryption / decryption key 10 includes bits B32, B34, B36, B38.
[0075] When the first set El of bits of the unlock word 20 is not identical to the first set El 1 of bits of the access key 18, the first comparison means 21 can command the first delivery means 12 so that it delivers a predetermined set of bits stored in the third memory 15.
[0076] The predetermined bit set has the same number of bits as the number of bits contained in the first bit set E21 of the first word of the encryption / decryption key 10, so that it has the same size as that of the first set E21. Each bit of the predetermined bit set is in a logic high or low state so that when the first bit set El of the unlock word 20 is not identical to the first bit set El1 of the access key 18, the delivered predetermined bit set resembles a part of the encryption / decryption key 10, misleading an attacker observing the output of the first delivery means 12.
[0077] Similarly, when the second set E2 of bits of the unlock word 20 is not identical to the second set E12 of bits of the access key 18, the second comparison means 22 can command the second delivery means 13 so that it delivers a predetermined set of bits stored in the fourth memory 16. The delivered predetermined set of bits resembles another part of the encryption / decryption key 10, misleading an attacker observing the output of the second delivery means 13.
[0078] Of course, the first word can include more or less than eight bits.
[0079] Alternatively, the encryption / decryption key 10 can be formed from several words.
[0080] Alternatively, the access key may comprise more or less than eight bits.
[0081] Figure 3 illustrates a second example of an embodiment of a key reading system encryption / decryption 10.
[0082] We find the first memory 11, the first register 14, the fourth memory 17 storing the access key 18 comprising eight bits B4[ to B48, and the second register 19 storing the unlock word 20 comprising bits B5i to B58.
[0083] In this embodiment, it is assumed that the encryption / decryption key 10 is formed by a first word 32 comprising, for example, thirty-two bits referenced B6i to B92 and a second word 33 for example of thirty-two bits referenced B 101 to B132 stored in the first memory 11.
[0084] The first and second words 32, 33 are stored in the first memory 11.
[0085] The encryption / decryption key 10 consists of sixty-four bits.
[0086] The reading system includes a first set of delivery means for delivering the bits B6[ to B92 of the first word 32 a second set of delivery means for delivering the bits BiOi to Bn2 of the second word 33.
[0087] The first set of delivery means includes, for example, a first delivery means 34, a second delivery means 35, a third delivery means 36 and a fourth delivery means 37.
[0088] The second set of delivery means comprises, for example, a third delivery means 38, a fourth delivery means 39, a first delivery means 40 and a second delivery means 4L
[0089] Each delivery means 34, 35, 36, 37, 38, 39, 40, 41 has 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] The second input of the first delivery means 34 of the first set of delivery means is connected to a fifth memory 42, the second input of the second delivery means 35 of the first set of delivery means is connected to a sixth memory 43, the second input of the third delivery means 36 of the first set of delivery means is connected to a seventh memory 44 and the second input of the fourth delivery means 37 of the first set of delivery means is connected to an eighth memory 45.
[0091] The second input of the third delivery means 38 of the second set of delivery means is linked to a ninth memory 46, the second input of the fourth delivery means 39 of the second set of delivery means is linked to a tenth memory 47, the second input of the first delivery means 40 of the second set of delivery means is linked to an eleventh memory 48 and the second input of the second delivery means 41 of the second set of delivery means is linked to a twelfth memory 49.
[0092] As shown, each delivery means 34, 35, 36, 37, 38, 39, 40, 41 comprises, for example, a multiplexer having a first input connected to the first input of the delivery means 34, 35, 36, 37, 38, 39, 40, 41, a second input connected to the second input of the delivery means 34, 35, 36, 37, 38, 39, 40, 41, and an output connected to the output of the delivery means 34, 35, 36, 37, 38, 39, 40, 41
[0093] The reading system further comprises a first comparison means 50, a second comparison means 51, a third comparison means 52 and a fourth comparison means 53.
[0094] Each comparison means 50, 51, 52, 53 has 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 means 50 is connected to the control input 34a of the first delivery means 34 of the first set of delivery means and connected to the control input 39a of the fourth delivery means 39 of the second set of delivery means.
[0096] The output of the second comparison means 51 is connected to the control input 35a of the second delivery means 35 of the first set of delivery means and connected to the control input 38a of the third delivery means 38 of the second set of delivery means.
[0097] The output of the third comparison means 52 is connected to the control input 36a of the third delivery means 36 of the first set of delivery means and connected to the control input 41a of the second delivery means 41 of the second set of delivery means.
[0098] The output of the fourth comparison means 53 is connected to the control input 37a of the fourth delivery means 37 of the first set of delivery means and connected to the control input 40a of the first delivery means 40 of the second set of delivery means.
[0099] Now, a method for implementing the second example of the reading system is described.
[0100] When the unlock word 20 is stored in the second register 19, the first comparison means 50 compares a first set E60 of bits of the unlock word 20 and a first set E50 of bits of the access key 18, the second comparison means 51 compares a second set E61 of bits of the unlock word 20 and a second set E51 of bits of the access key 18, the third comparison means 52 compares a third set E62 of bits of the unlock word 20 and a third set E52 of bits of the access key 18, and the fourth comparison means 53 compares a fourth set E63 of bits of the unlock word 20 and a fourth set E53 of bits of the access key 18.
[0101] Each set 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 the plurality of bits of the access key 18, each bit being different.
[0102] Alternatively, each set of the first, second, third and fourth sets E50, E51, E52, E53 of bits of the access key 18 comprises a plurality of bits of the access key 18, the plurality of bits of each set of the first, second, third and fourth sets E50, E51, E52, E53 being different.
[0103] In what follows, it is assumed that the first set E50 of bits of the access key 18 includes bits B4H B42, B47, B48, that the second set E51 of bits of the access key 18 includes bits B43, B^, B45, B46, that the third set E52 of bits of the access key 18 includes bits B4b B^, B45, B48 and that the fourth set E53 of bits of the access key 18 includes bits B42, B43, B46, B47 so that the bits of each set E50, E51, E52, E53 do not follow one another.
[0104] If the first set of bits E60 of the unlock word 20 is identical to the first set E50 of bits of the access key 18, the first comparison means 50 drives the first delivery means 34 of the first set of delivery means so that it delivers a first set E34 of bits of the first word 32 and drives the fourth delivery means 39 of the second set of delivery means so that it delivers a second set E39 of bits of the second word 33.
[0105] If the second bit set E61 of the unlock word 20 is identical to the second bit set E51 of the access key 18, the second comparison means 51 drives the second delivery means 35 of the first delivery means set so that it delivers a second bit set E35 of the first word 32 and drives the third delivery means 38 of the second delivery means set so that it delivers a first bit set E38 of the second word 33.
[0106] If the third bit set E62 of the unlock word 20 is identical to the third bit set E52 of the access key 18, the third comparison means 52 drives the third delivery means 36 of the first delivery means set so that it delivers a third bit set E36 of the first word 32 and drives the second delivery means 41 of the second delivery means set so that it delivers a fourth bit set E41 of the second word 33.
[0107] If the fourth bit set E63 of the unlock word 20 is identical to the fourth bit set E53 of the access key 18, the fourth comparison means 53 drives the fourth delivery means 37 of the first delivery means set so that it delivers a fourth bit set E37 of the first word 32 and drives the first delivery means 40 of the second delivery means set so that it delivers a third bit set E40 of the second word 33.
[0108] The first, second, third and fourth sets E34, E35, E36, E37 of bits of the first word 32 form the first word 32 and the first, second, third and fourth sets E38, E39, E40, E41 of bits of the second word 33 form the second word 33.
[0109] The sets E34, E35, E36, E37, E38, E39, E40, E41 of bits of the first and second words 32, 33 delivered by the delivery means are for example stored in the first register 14.
[0110] It is assumed that the first set E34 of bits of the first word 32 includes, for example, the bits B6i, B65, B69, B73, B77, B8b, B85, B89 of the first word 32, the second set E35 of bits of the first word 32 includes, for example, the bits B62, B66, B70, B74, B78, B82, B86, B90 of the first word 32, the third set E36 of bits of the first word 32 includes, for example, the bits B63, B67, B7b, B75, B79, B83, B87, B9i of the first word 32, and the fourth set E37 of bits of the first word 32 includes, for example, the bits BM, B68, B72, B76, B80, B84, B88, B92 of the first word 32.
[0111] It is assumed that the first set E38 of bits of the second word 33 comprises, for example, the bits Bi01, Bi02, B109, Bn3, Bn7, B121, B125, B129 of the second word 33, the second set E39 of bits of the second word 33 comprises, for example, the bits B102, B106, B110, B114, B118, B122, B126, B130 of the second word 33, the third set E40 of bits of the second word 33 comprises, for example, the bits B103, B107, Bm, Bn5, B119, B123, B127, B131 of the second word 33, and the fourth set E41 of bits of the second word 33 comprises, for example, the bits Bi04, Bi08, Bn2, Bn6, Bi20, B24, Bi28, B[32 second word 33.
[0112] The bits of each set E34, E35, E36, E37, E38, E39, E40, E41 of words 32, 33 do not follow one another.
[0113] Of course, as an alternative, only the bits of one or more sets E34, E35, E36, E37, E38, E39, E40, E41 of words 32, 33 do not follow one another.
[0114] To obtain the full encryption / decryption key 10, it is necessary to fulfill four different conditions.
[0115] It is necessary that the bits of the first bit set E60 of the unlock word 20 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, that the bits of the second bit set E61 of the unlock word 20 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, that the bits of the third bit set E62 of the unlock word 20 be 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 that 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, it is necessary to deploy four lasers to force the release of the key 10 by the delivery means 34, 35, 36, 37, 38, 39, 40, 41, thus making the reading system more robust compared to a known reading system of the state of the art.
[0117] As described above, the memories 42, 43, 44, 45, 46, 47, 48, 49 can each contain a series of eight bits, each corresponding to a part of the encryption / decryption key 10, so that when one of the delivery means 34, 35, 36, 37, 38, 39, 40, 41 is commanded to connect its output to its second input, said delivery means delivers the series of bits contained in the memory connected to said second input.
[0118] Of course, the encryption / decryption key 10 can be formed of more than two words, each word having more or less thirty-two bits.
Claims
Demands
1. A method for reading an encryption / decryption key (10) comprising at least a first word (32) comprising a plurality of bits (B3i, B32, B33, B34, B35, B36, B37, B38, B6i, B92), the method comprising: - a first comparison of a first set (Ei) of bits (B5i, B53, B55B57) of an unlock word (20) comprising a plurality of bits (B5i, B52, B53, B54, B55, B56, B57, B58) and a first set (En) of bits of an access key (18), the first set (En) of bits (B4b B43, B45B47) of the access key (18) comprising at least one first bit of the plurality of bits (B4b B42, B43, B44, B45, B46, B47, B48) of the access key, - the delivery of at least a first set (E2i) of bits (B3i, B33, B35, B37) of the first word of the encryption / decryption key if the first set (EJ) of bits of the unlock word (20) is identical to the first set (En) of bits of the access key (18), the first set (E2i) of bits being chosen from the plurality of bits (B3b, B32, B33, B34, B35, B36, B37, B38, B6i, B92) of the first word, - at least one second comparison of a second set (E2) of bits (B52, B54, B56, B58) of the unlock word (20) different from the first set (EJ) of bits of the unlock word and a second set (En) of bits (B42, B44, B46, B48) of the access key (18), the second set (En) of bits of the access key (18) comprising at least one second bit from the plurality of bits of the access key different from the first bit, and - a delivery of at least a second set (E22) of bits (B32, B34, B36jB38) of the first word of the encryption / decryption key if the second set (E2) of bits of the unlock word (20) is identical to the second set (E[2] of bits of the access key (18), the second set of bits being chosen from the plurality of bits of the first word and different from the bits of the first set of bits, the union of the sets of bits of the first word forming the first word.
2. Method according to claim 1, the encryption / decryption key (10) comprising at least a second word (33) comprising a plurality of bits (Bioi, B132), the method comprising: - delivering at least a first set of bits of the second word (33) of the encryption / decryption key (10) when the first set (EJ) of bits of the unlock word (20) is identical to the first set (En) of bits of the access key (18), the first set of bits of the second word (33) being chosen from the plurality of bits of the second word, and - delivering at least a second set of bits of the second word (33) of the encryption / decryption key (10) if the second set (E2) of bits of the unlock word (20) is identical to the second set (Ei2) of bits of the access key (18), the second set of bits of the second word (33) being chosen from the plurality of bits of the second word and different from the bits of the first set of bits of the second word (33),the combination of the bit sets of the second word forming the second word (33) and the first and second words forming the encryption / decryption key (10).
3. A method according to claim 1 or 2, wherein the bits of at least one set (E2b E22) of bits of the encryption / decryption key are chosen so that said bits do not follow one another.
4. A method according to any one of claims 1 to 3, wherein when a set (Eb E2) of bits of the unlock word (20) is not identical to a set (En, Ei2) of bits of the access key (18), the method comprises delivering a set of predetermined bits having the same size as the set of bits associated with said comparison.
5. A method according to any one of claims 1 to 4, wherein the first set (Ei2) of bits of the access key (18) comprises the first bit of the access key and a first combination of bits selected from the plurality of bits of the access key (18), the bits of the first combination being different from the first and second bits of the access key (18), and the second set (Ei2) of bits of the access key (18) comprises the second bit and a second combination of bits selected from the plurality of bits of the unlock word, the bits of the
6. the second combination being different from the first bit, the second bit and the bits of the first combination. A system for reading an encryption / decryption key (10) comprising at least one first word (32) comprising a plurality of bits (B3i, B32, B33, B34, B35, B36, B37, B38, B61, B92), the system comprising: - a first comparison means (21, 50) configured to compare a first set (EJ) of bits (B5i, B53, B55B57) of an unlock word (20) comprising a plurality of bits (B5i, B52, B53, B54, B55, B56, B57, B58) and a first set (En) of bits (B41, B43, B45B47) of an access key (18), the first set of bits of the access key (18) comprising at least one first bit of the plurality of bits (B41, B42, B43, B44, B45, B46, B47, B48) of the access key (18), - a first delivery means (12, 34) configured to deliver at least a first set (E2i) of bits (Bîh B33, B35 B37) of the first word of the encryption / decryption key (10) if the first set of bits of the unlock word (20) is identical to the first set of bits of the access key (18), the first set of bits being chosen from the plurality of bits of the first word, - a second comparison means (22, 51) configured to compare a second set (E2) of bits (B52, B54, B56, B58) of the unlock word (20) different from the first set (EJ) of bits of the unlock word and a second set (E12) of bits of the access key (18), the second set of bits of the access key (18) having at least one second bit from the plurality of bits of the access key different from the first bit, and - a second delivery means (13, 35) configured to deliver at least a second set (E22) of bits (B32, B34, B36, B38) of the first word of the encryption / decryption key if the second set (E2) of bits of the unlock word (20) is identical to the second set (Ei2) of bits of the access key (18), the second set of bits being chosen from the plurality of bits of the first word and different from the bits of the first set of bits, the union of the sets of bits from the first word forming the first word.
7. System according to claim 6, the encryption / decryption key (10) comprising at least a second word (33) comprising a plurality of bits (Bioi, Bi32), the system comprising: - a third delivery means (38) configured to deliver at least a first set (E38) of bits of the second word (33) of the encryption / decryption key (10) if the first set (Ei) of bits of the unlock word is identical to the first set of bits of the access key, the first set of bits being chosen from the plurality of bits of the first word, and - a fourth delivery means (39) configured to deliver at least a second set (E39) of bits of the second word (33) of the encryption / decryption key (10) if the second set (E2) of bits of the unlock word (20) is identical to the second set (Ei2) of bits of the access key (18),the second set of bits being chosen from the plurality of bits of the first word and different from the bits of the first set of bits, the union of the sets of bits of the second word forming the first word.
8. System according to claim 6 or 7, wherein the bits of at least one set of bits of the encryption / decryption key (10) are chosen so that said bits do not follow one another.
9. A system according to any one of claims 6 to 8, wherein at least one delivery means (12, 13, 34, 35, 36, 37, 38, 39, 40) is configured to deliver a predetermined set of bits when the bit set of the unlock word (20) associated with said delivery means is not identical to a bit set of the access key (18), the predetermined bit set having the same size as the bit set associated with said comparison.
10. A system according to any one of claims 6 to 9, wherein the first set (En) of bits of the access key (18) comprises the first bit of the access key and a first combination of bits selected from the plurality of bits of the access key (18), the bits of the first combination being different from the first and second bits of the access key (18), and the second set (Ei2) of bits of the access key (18) comprises the second bit and a second combination of bits chosen from the plurality of bits of the unlock word, the bits of the second combination being different from the first bit, the second bit and the bits of the first combination.