CN111901097B - White box implementation method and device, electronic equipment and computer storage medium - Google Patents
White box implementation method and device, electronic equipment and computer storage medium Download PDFInfo
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- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/06—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols the encryption apparatus using shift registers or memories for block-wise or stream coding, e.g. DES systems or RC4; Hash functions; Pseudorandom sequence generators
- H04L9/0618—Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation
- H04L9/0625—Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation with splitting of the data block into left and right halves, e.g. Feistel based algorithms, DES, FEAL, IDEA or KASUMI
Abstract
The disclosure provides a white box implementation method, a white box implementation device, electronic equipment and a computer storage medium, and to-be-processed data is acquired; determining first preset number of round operations and second preset number of round operations of the Feistel structure type cipher algorithm as target round operations; when target round operation is carried out according to the Feistel structure type cipher algorithm, round operation is carried out on corresponding data based on a lookup table of the target round operation to obtain a corresponding round operation result, and a processing result of the data to be processed after the Feistel structure type cipher algorithm operation is carried out is obtained based on the round operation result, so that the safety is high; the first preset number and the second preset number are both greater than or equal to the branch number of the Feistel structure type cipher algorithm, and the total round number of the target round operation is less than or equal to the total round number of the Feistel structure type cipher algorithm; the lookup table includes a lookup table generated based on the round key and the round function of the target round operation.
Description
Technical Field
The present disclosure relates to the field of information security technologies, and in particular, to a white box implementation method and apparatus, an electronic device, and a computer storage medium.
Background
With the popularization of networks and intelligent terminals, such as mobile phones, tablets, computers and the like, in order to protect the security of various private data in the intelligent terminals, the intelligent terminals need to encrypt and decrypt data stored by the intelligent terminals by using a cryptographic algorithm, for example, the data is encrypted and decrypted by using a Feistel structure cryptographic algorithm. The Feistel-type structure cryptographic algorithm is a common cryptographic algorithm structure, and numerous cryptographic algorithms such as DES, SM4 and RC5 are Feistel-type structures.
However, because the environment of the intelligent terminal is often uncontrollable, an attacker or a malicious user may obtain an intermediate calculation result in the encryption and decryption operation process of the Feistel structure type cryptographic algorithm through reverse engineering and other technologies, and then easily extract or reply a key used by the Feistel structure type cryptographic algorithm, so that the security of data is threatened, and the security of the Feistel structure type cryptographic algorithm is reduced.
To solve this problem, it is proposed to implement a white-box implementation of the cryptographic algorithm to protect the security of the key. However, the existing white box implementation scheme of the cryptographic algorithm constructed by people is difficult to achieve good balance in the aspects of security, storage, efficiency and the like, and the actual use effect is not good.
In summary, how to improve the key security of the Feistel structure type cipher algorithm when the untrusted terminal runs is a problem to be solved urgently by those skilled in the art at present.
Disclosure of Invention
The purpose of the disclosure is to provide a white box implementation method, which can solve the technical problem of how to improve the key security of the Feistel structure type cryptographic algorithm when the untrusted terminal runs to a certain extent. The disclosure also provides a white box implementation device, an electronic device and a computer readable storage medium.
According to a first aspect of the embodiments of the present disclosure, there is provided a white box implementation method, including:
acquiring data to be processed;
determining first preset number of round operations before and second preset number of round operations after the Feistel structure type cipher algorithm as target round operations;
when target round operation is carried out according to the Feistel structure type cipher algorithm, round operation is carried out on data corresponding to the data to be processed based on a lookup table of the target round operation to obtain a corresponding round operation result, and a processing result of the data to be processed after the Feistel structure type cipher algorithm operation is carried out is obtained based on the round operation result;
the first preset number and the second preset number are both greater than or equal to the number of branches of the Feistel structure type cipher algorithm, and the sum of the first preset number and the second preset number is less than or equal to the total round number of the Feistel structure type cipher algorithm; the lookup table includes a lookup table generated based on the round key and the round function of the target round operation.
Preferably, the method further comprises the following steps:
when non-target round operation is performed according to the Feistel structure type cipher algorithm, round operation is performed on data corresponding to the data to be processed based on the round key after mask protection to obtain a corresponding round operation result, and the processing result is obtained based on the round operation result.
Preferably, the number of branches of the Feistel structure type cipher algorithm includes 2, and before the round operation is performed on the data corresponding to the data to be processed based on the lookup table of the target round operation, the method further includes:
acquiring a key and a round function of the Feistel structure type cryptographic algorithm;
generating a corresponding round key through a key expansion algorithm based on the key;
generating a random permutation function and a random vector;
constructing a lookup table by a lookup table generation formula based on the round key, the round function, the random permutation function and the random vector;
the look-up table generation formula comprises:
wherein f represents the random permutation function; g represents the random permutation function; k is i A round key representing an ith round of target round operations; f represents a round function of the Feistel structure type cipher algorithm; t is t 1 Representing the first preset number; t is t 2 Representing the second preset number; n represents the total round number of the Feistel structure type cipher algorithm; Δ' represents the random vector; delta i ＝Δ' i-1 ；
Representing an exclusive or operation.
Preferably, before the round operation is performed on the data corresponding to the data to be processed by the lookup table based on the target round operation, the method further includes:
generating the mask protected round key through a mask round key generation formula based on the random vector;
the mask round key generation formula comprises:
wherein, K' i Representing the mask protected round keys.
Preferably, the round operation is performed on the data corresponding to the data to be processed based on the mask-protected round key to obtain a corresponding round operation result, including:
performing round operation on data corresponding to the data to be processed based on the mask protected round key through a non-target round operation formula to obtain a corresponding round operation result;
the non-target round operation formula comprises:
L' i ＝R′ i-1 、
wherein, L' i The first data to be processed, R ', representing the i +1 th wheel calculation' i And representing the second data to be processed of the (i + 1) th round operation.
Preferably, the determining, as the target round operation, the first preset number of round operations before and the second preset number of round operations after the Feistel structure type cipher algorithm includes:
determining a first preset number of round operations before and a second preset number of round operations after the Feistel structure type cipher algorithm as the target round operations according to preset conditions;
the preset conditions comprise storage safety conditions, storage space conditions and operation efficiency conditions.
Preferably, before the constructing the lookup table by the lookup table generation formula based on the round key, the round function, the random permutation function, and the random vector, the method further includes:
determining the scale of the lookup table according to preset conditions;
the preset conditions comprise storage safety conditions, storage space conditions and operation efficiency conditions.
According to a second aspect of the embodiments of the present disclosure, there is provided a white box implementing apparatus, including:
the first acquisition module is used for acquiring data to be processed;
the first determining module is used for determining a first preset number of round operations before and a second preset number of round operations after the first preset number of round operations of the Feistel structure type cipher algorithm as target round operations;
the first operation module is used for performing round operation on data corresponding to the data to be processed based on a lookup table of the target round operation to obtain a corresponding round operation result when the target round operation is performed according to the Feistel structure type cryptographic algorithm, so as to obtain a processing result of the data to be processed after the Feistel structure type cryptographic algorithm is performed based on the round operation result;
the first preset number and the second preset number are both greater than or equal to the number of branches of the Feistel structure type cipher algorithm, and the sum of the first preset number and the second preset number is less than or equal to the total round number of the Feistel structure type cipher algorithm; the lookup table includes a lookup table generated based on the round key and the round function of the target round operation.
According to a third aspect of an embodiment of the present disclosure, there is provided an electronic apparatus including:
a memory having a computer program stored thereon;
a processor for executing the computer program in the memory to implement the steps of any of the methods described above.
According to a fourth aspect of embodiments of the present disclosure, there is provided a computer readable storage medium, on which a computer program is stored, which program, when executed by a processor, performs the steps of any of the methods described above.
The white box implementation method provided by the disclosure is used for acquiring data to be processed; determining first preset number of round operations before and second preset number of round operations after the Feistel structure type cipher algorithm as target round operations; when target round operation is carried out according to a Feistel structure type cipher algorithm, round operation is carried out on data corresponding to the data to be processed based on a lookup table of the target round operation to obtain a corresponding round operation result, and a processing result of the data to be processed after the Feistel structure type cipher algorithm operation is carried out is obtained based on the round operation result; the first preset number and the second preset number are both greater than or equal to the number of branches of the Feistel structure type cipher algorithm, and the sum of the first preset number and the second preset number is less than or equal to the total round number of the Feistel structure type cipher algorithm; the lookup table includes a lookup table generated based on the round key and the round function of the target round operation. According to the white box implementation method, the round key and the round function of the target round operation are hidden by means of the lookup table, so that an attacker cannot acquire the accurate round key and the round function even in an untrusted terminal, the Feistel structure type cryptographic algorithm cannot be attacked, and the safety is good. In addition, the white box implementation method provided by the disclosure can protect the Feistel structure type cipher algorithm only by hiding the round key and the round function in the round operation of the first preset number and the second preset number in the front and the second preset number, and the efficiency is high. The white box implementation device, the electronic equipment and the computer readable storage medium provided by the disclosure also solve the corresponding technical problems.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present disclosure, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a first flowchart illustrating a white-box implementation in accordance with an exemplary embodiment;
FIG. 2 is a schematic diagram of an encryption operation of a conventional 2-branch Feistel structure-like cryptographic algorithm;
fig. 3 is a schematic diagram illustrating a decryption operation of a conventional 2-branch Feistel structure-based cipher algorithm;
FIG. 4 is a schematic diagram illustrating the operation of a 2-branch Feistel structure-like cryptographic algorithm according to the present disclosure;
FIG. 5 shows the first t of the present embodiment 1 A round lookup process graph;
FIG. 6 shows the middle n-t of this embodiment 1 -t 2 A round lookup process graph;
FIG. 7 shows the result t of the present embodiment 2 A round lookup process graph;
FIG. 8 is a schematic diagram illustrating a white-box implementation in accordance with an exemplary embodiment;
fig. 9 is a block diagram illustrating an electronic device 900 in accordance with an example embodiment.
Detailed Description
The technical solutions in the embodiments of the present disclosure will be described clearly and completely with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the embodiments described are only some embodiments of the present disclosure, rather than all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.
Referring to fig. 1, fig. 1 is a first flowchart illustrating a white-box implementation method according to an exemplary embodiment.
The white box implementation method related by the disclosure can comprise the following steps:
step S101: and acquiring data to be processed.
It is to be understood that the data to be processed may be determined according to an application scenario, for example, the data to be processed may be video data in a video transmission process. The type of the data to be processed may also be determined according to an application scenario, for example, the data to be processed may be data to be encrypted or the like, and may also be data to be decrypted or the like; when the data to be processed is the data to be encrypted, the encryption operation of the data to be processed is realized by means of a Feistel structure type cipher algorithm, and when the data to be processed is the data to be decrypted, the decryption operation of the data to be processed is realized by means of the Feistel structure type cipher algorithm. It should be noted that, when the corresponding operation of the data to be processed is implemented by using the Feistel structure type cipher algorithm, the data to be processed needs to be split according to the number of branches of the Feistel structure type cipher algorithm, for example, when the number of branches of the Feistel structure type cipher algorithm is 3, the data to be processed is split into 3 segments of data, and the like.
Step S102: determining first preset number of round operations and second preset number of round operations of the Feistel structure type cipher algorithm as target round operations; the first preset number and the second preset number are both greater than or equal to the number of branches of the Feistel structure type cipher algorithm, and the sum of the first preset number and the second preset number is less than or equal to the total round number of the Feistel structure type cipher algorithm.
It can be understood that after the data to be processed is obtained, a first preset number of round operations before and a second preset number of round operations after the Feistel structure type cryptographic algorithm are determined as target round operations, and both the first preset number and the second preset number are greater than or equal to the number of branches of the Feistel structure type cryptographic algorithm, so as to ensure that when the Feistel structure type cryptographic algorithm is implemented in a white box, the round keys of the first preset number of round operations before and the second preset number of round operations after the first preset number of round operations are safe, because when the first preset number is equal to the number of branches of the Feistel structure type cryptographic algorithm, when the first preset number of round operations before is completed in a table look-up manner, the coding of the internal state of the algorithm can be implemented, so that the round keys in the first preset number of round operations before are protected, similarly, when the second preset number is equal to the number of branches of the Feistel structure type cryptographic algorithm, the second preset number of round operations before and the second preset number of round operations after the second preset number of round operations is protected, and the second preset number of round operations can be just as the plaintext output, so that the second preset number of round keys is just as the protection of the plaintext protection of the round operations after the second preset number of the round operations, can be implemented. With the increase of the first preset number and the second preset number, the safety of the Feistel structure type cipher algorithm white box implementation is increased, but the operation efficiency is reduced. It should be noted that the first preset number of round operations refers to a first preset number of round operations from the first number of Feistel structure-based cryptographic algorithm round operations; the second preset number of round operations refers to the second preset number of round operations counted from the back of the Feistel structure type cryptographic algorithm round operations.
Step S103: when target round operation is carried out according to a Feistel structure type cipher algorithm, round operation is carried out on data corresponding to the data to be processed based on a lookup table of the target round operation to obtain a corresponding round operation result, and a processing result of the data to be processed after the Feistel structure type cipher algorithm operation is carried out is obtained based on the round operation result; the lookup table includes a lookup table generated based on the round key and the round function of the target round operation.
It can be understood that after the target round operation is determined, the data to be processed needs to be operated according to a Feistel structure type cipher algorithm, and in the process, when the target round operation is performed, the round operation needs to be performed on the data corresponding to the data to be processed based on the lookup table of the target round operation to obtain a corresponding round operation result; when the non-target round operation is carried out, the operation can be carried out according to the round operation definition of the Feistel structure type cipher algorithm. That is, when round operation is performed according to the Feistel structure type cipher algorithm, operation needs to be performed by means of a lookup table generated by a round key and a round function in target round operation, and operation can be performed by means of the round key and the round function directly in non-target round operation.
The look-up table to which the present disclosure relates is defined as follows: for the function y = f (x), traversing the input value x and storing the corresponding output values y as a table in the traversal order, so that given an input value, the table can be queried based on the input value to obtain the corresponding output value; by means of look-up tables both the function can be implemented and the structure of the function can be hidden, e.g. assuming
When both functions g and h are double-mapped, if only the lookup table is known, no information of the functions g and h can be obtained, because for any bijective g, one bijective h can be found, so that the composite mapping function f of the two functions generates the same lookup table. Therefore, the round function and the round key in the target round operation can be hidden by the lookup table, and the protection of the round key of the Feistel structure type cipher algorithm is realized. />
The white box implementation method provided by the present disclosure obtains data to be processed; determining first preset number of round operations and second preset number of round operations of the Feistel structure type cipher algorithm as target round operations; when target round operation is carried out according to a Feistel structure type cipher algorithm, round operation is carried out on data corresponding to the data to be processed based on a lookup table of the target round operation to obtain a corresponding round operation result, and a processing result of the data to be processed after the Feistel structure type cipher algorithm operation is carried out is obtained based on the round operation result; the first preset number and the second preset number are both greater than or equal to the number of branches of the Feistel structure type cipher algorithm, and the sum of the first preset number and the second preset number is less than or equal to the total round number of the Feistel structure type cipher algorithm; the look-up table comprises a look-up table generated based on the round key and the round function of the target round operation. According to the white box implementation method, the round key and the round function of the target round operation are hidden by means of the lookup table, so that an attacker cannot acquire the accurate round key and the round function even in an untrusted terminal, the Feistel structure type cryptographic algorithm cannot be attacked, and the safety is good. In addition, the white box implementation method provided by the disclosure can protect the Feistel structure type cipher algorithm only by hiding the round key and the round function in the round operations of the first preset number and the second preset number by means of the lookup table, and the efficiency is high; and need not carry out outer coding, the data exchange of being convenient for.
In the white box implementation method related in the present disclosure, the number of branches of the Feistel structure type cipher algorithm may include 2; at this time, when round operation is performed on the data corresponding to the data to be processed based on the lookup table of the target round operation, a first lookup result corresponding to a second data to be processed in the target round operation can be looked up in the lookup table t.j.1 of the target round operation; searching a first to-be-processed data in the target round operation and a second search result corresponding to the first search result in the round in a search table T.j.2 of the target round operation; j represents the number of rounds of the target round operation in the Feistel structure type cipher algorithm. Referring to fig. 2, fig. 3 and fig. 4, fig. 2 is a schematic diagram illustrating an encryption operation of a conventional 2-branch Feistel-structure-type cipher algorithm; FIG. 3 is a schematic diagram illustrating a decryption operation of a conventional 2-branch Feistel-structured cipher algorithm; FIG. 4 is a schematic diagram illustrating the operation of a 2-branch Feistel structure-like cryptographic algorithm according to the present disclosure; wherein L is 0 Representing Feistel structuresLeft branch of cryptographic algorithm, R 0 Representing the right branch of the Feistel structure class cipher algorithm. As can be seen from fig. 2, fig. 3, and fig. 4, the white-box implementation method provided by the present disclosure can protect the round key and the round function in the target round operation from being obtained by an attacker, and has good security.
For convenience of understanding, the construction mode of the lookup table in the target round operation and the encryption and decryption correctness and security of the white-box implementation method provided by the disclosure are analyzed by combining the encryption process of the Feistel structure type cipher algorithm. The process of encryption operation of the existing Feistel structure type cipher algorithm is as follows: (L) 0 ,R 0 )＝P；L i ＝R i-1 ；
C＝(R n ,L n ) (ii) a Wherein P represents plaintext information, C represents ciphertext information, i represents the number of rounds of round calculation, F represents a round function, K represents the number of rounds of round calculation i A round key representing the ith round of operation. According to the encryption operation process of the Feistel structure type cipher algorithm, when a lookup table is constructed, random permutation f can be generated firstly 1 ,f 2 ,…,f n ,g 1 ,g 2 ,…,g n-1 And then generates a look-up table>
And g is a -1 ,g 0 ,g n-1 ,g n Are all identical transformations.
When performing an encryption operation according to the structure shown in fig. 4 based on the generated lookup table, R 0 Y is obtained after being inquired by a look-up table T.1.1 0 The construction of the look-up table indicates y 0 ＝f 1 (F(R 0 ,K 1 ))；(L 0 ,y 0 ) Obtaining R 'after being inquired by a lookup table T.1.2' 1 R 'is known' 1 ＝g 1 (R 1 ) (ii) a In round 2, R' 1 Y is obtained after being inquired by a lookup table T.2.1 1 Easy to know
Then (L) 1 ,y 1 ) Warp beamObtaining R 'after inquiring according to a table T.2.2' 2 R 'is readily known' 2 ＝g 2 (R 2 ) At this time L' 2 ＝R′ 1 ＝g 1 (L 2 ). Correspondingly, L 'can be obtained by sequentially querying the lookup table' i ＝g i-1 (L i ),R′ i ＝g i (R i ) I =3,4, \ 8230;, n-2. At n-1 th wheel, R 'first' n-2 Obtaining y after being inquired by a look-up table T. (n-1) 1 n-2 Easy to know y n-2 ＝f n-1 (F(R n-2 ,K n-1 ) ); then (L' n-2 ,y n-2 ) Obtaining R 'after being inquired by a query table T. (n-1). 2' n-1 Easy to know>
At this time, L' n-1 ＝R' n-2 ＝g n-2 (L n-1 ). At the last round, R' n-1 I.e. R n-1 Y is obtained after being inquired by a lookup table T.n.1 n-1 Easy to know y n-1 ＝f n (F(R n-1 ,K n ) ); then (L' n-1 ,y n-1 ) Obtaining R 'after being inquired by a lookup table T.n.2' n Easy to know>
At this time L' n ＝R' n-1 ＝R n-1 ＝L n Therefore, the encrypted ciphertext obtained by the white box implementation method provided by the disclosure is the same as the ciphertext obtained by directly encrypting the plaintext by using the Feistel structure type cipher algorithm.
After the encryption correctness is analyzed, the security is analyzed: when the permutation functions f, g are random permutation functions, the mappings f, g cannot be separated from the lookup tables provided by the present disclosure, such as the given lookup table t.j.1, for any given random permutation
Or K j There is always a mapping f such that the constructed look-up table is identical to t.j.1, so that no information about the round key K can be obtained from the look-up table j Any of (3). It is easy to know that combining multiple lookup tables is not available for the same reasonGet the key K of the round j The information of (1). Therefore, the white box implementation method has the advantages that the round operations of the first preset number in the front and the round operations of the second preset number in the rear have safety, and the round keys of the corresponding rounds can be effectively protected. In practical application, due to limitations such as storage, random permutation may not be randomly selected from the whole permutation space, and at this time, the security of round keys of the first preset number of round operations and the second preset number of round operations may be reduced to a certain extent, and random permutation may be selected within a reasonable range according to actual security and storage requirements.
In the white box implementation method provided by the present disclosure, in order to improve the security of the white box implementation method, when performing non-target round operation according to a Feistel structure type cipher algorithm, round operation may be performed on data corresponding to data to be processed based on a round key protected by a mask to obtain a corresponding round operation result, so as to obtain a processing result based on the round operation result.
In the white box implementation method provided by the disclosure, in order to improve the operation efficiency of the white box implementation method, the scale of the white box implementation method can be reduced by combining the cyclic difference characteristic of the Feistel structure type cryptographic algorithm, and before performing round operation on data corresponding to the data to be processed based on the lookup table of the target round operation, a key and a round function of the Feistel structure type cryptographic algorithm can be obtained; generating a corresponding round key through a key expansion algorithm based on the key; generating a random permutation function and a random vector; constructing a lookup table by a lookup table generation formula based on the round key, the round function, the random permutation function and the random vector;
the look-up table generation formula comprises:
wherein f represents a random permutation function; g represents a random permutation function; k i A round key representing an ith round of target round operations; f represents a round function of the Feistel structure type cipher algorithm; t is t 1 Indicating a first preset number；t 2 Representing a second preset number; n represents the total round number of the Feistel structure type cipher algorithm; Δ' represents a random vector; delta i ＝Δ' i-1 ；
Representing an exclusive or operation; />
Representing a multiplication operation.
Correspondingly, the mask-protected round key can be generated through a mask round key generation formula based on the random vector; the mask round key generation formula may include:
wherein, K' i Indicating the mask protected round keys. Then, when performing round operation on the data corresponding to the data to be processed based on the round key after mask protection to obtain a corresponding round operation result, performing round operation on the data corresponding to the data to be processed based on the round key after mask protection through a non-target round operation formula to obtain a corresponding round operation result; the non-target round robin formulation may include:
L' i ＝R′ i-1 、
wherein, L' i The first data to be processed, R ', representing the i +1 th wheel calculation' i And representing the second data to be processed of the (i + 1) th round operation.
Wherein, when performing non-target wheel calculation according to the Feistel structure type cipher algorithm, the formula L 'is passed' i ＝R′ i-1 、
Performing round operation; l' i Indicating the i +1 th wheelFirst data to be processed of an operation, R i ' denotes the second data to be processed of the (i + 1) th round of operation.
Because the round function of the Feistel structure type cipher algorithm meets the following characteristics:
wherein the function g is determined by a round function F; that is, when the input information (X, K) of the function F is simultaneously given with the specific difference Δ, g (Δ), respectively, the output information of the round function F remains unchanged, and accordingly, the lookup table can be constructed according to the lookup table generation formula in the embodiment, so that the white-box implementation method provided by the present disclosure has a lower storage space and higher operation efficiency.
Now, the correctness and security of encryption and decryption of the white-box implementation method provided in this embodiment are analyzed with reference to fig. 5, fig. 6, and fig. 7. FIG. 5 shows the first t of the present embodiment 1 Round looking up a table process diagram; FIG. 6 shows the middle n-t of the present embodiment 1 -t 2 Round looking up a table process diagram; FIG. 7 shows the result t of the present embodiment 2 And (5) checking the process chart in turn.
From top t 1 As can be seen from the structure of the round lookup table and FIG. 5, the time t is before 1 After round table look-up operation, the intermediate operation result is obtained
The following relationship is satisfied: />
Then, sequentially calculate
And/or>
The calculation process is similar, and the judgment result shows that the judgment result is greater than or equal to>
Finally, FIG. 7 shows the result 2 The construction process of the round lookup table can be known, and the finally obtained operation result R n ||L n The encryption result obtained by the implementation of the Feistel structure type cipher algorithm standard is the same, that is, the white box implementation method provided by this embodiment has the encryption and decryption correctness.
After the correctness of the encryption and decryption of the embodiment is verified, the security of the embodiment is analyzed: first, in a white-box attack environment, an attacker can obtain all intermediate operation processes of the Feistel structure type cryptographic algorithm, that is, the attacker can obtain the intermediate operation processes in this embodiment
Then, the difficulty of an attacker for acquiring the round key from the information is analyzed, and the information acquired by the attacker has the following relationship:
because of the fact that
To any of delta' i-1 All are true, thus, only R is known i ' -1 ,K i In the case of' K cannot be obtained from this calculation i Any information of (2), in turn due to
So that the wheel key->
Is completely dependent on random numbers +>
When the random numbers are not acquired, the information of the round keys cannot be acquired; upon observing the above relationship, an attacker can obtain a reference on @>
Useful information of (a) is:
due to the fact that
The attacker can thus obtain the following relationships:
n-t above 1 -t 2 The total number of n-t in the linear equation 1 -t 2 +2 variables
The number of possible values of these variables is thus the size of the space of values of two of these variables, according to Δ' 2 And delta' 4 Is known to be 2 N Where N is the packet length of the algorithm, i.e., the binary length of the plaintext message. As explained above, in a white-box attack environment, only the middle n-t is considered 1 -t 2 The complexity of recovering the round keys of the rounds is 2 N . Thus, the attacker can see n-t from the middle 1 -t 2 Useful information about the key of the wheel cannot be obtained in the wheel, and the safety of the scheme is mainly determined by the top t 1 Wheel and rear t 2 Safety determination of the wheel, i.e. if it is preceding t 1 In or behind the wheel t 2 In the round, the round key information and the random number information contained in the lookup table are effectively protected, so that the whole scheme is safe.
In the white box implementation method provided by the disclosure, because the number of rounds of target round operation can affect the security, the storage space occupancy rate, the operating efficiency and the like of the white box implementation method, when the first preset number of rounds of operation and the second preset number of rounds of operation of the Feistel structure type cryptographic algorithm are determined as the target round operation, in order to enable the white box implementation method provided by the disclosure to meet the requirement set by the outside, the first preset number of rounds of operation and the second preset number of rounds of operation of the Feistel structure type cryptographic algorithm can be determined as the target round operation according to the preset condition; the preset conditions may include a storage security condition, a storage space condition, and an operation efficiency condition.
In the white box implementation method provided by the present disclosure, due to the resolvability of the lookup table, in order to reduce the scale of the scheme or improve the efficiency of the scheme, the scale of the lookup table may be determined according to a preset condition, for example, the number of lookup tables implementing a certain operation is determined, and then, before the lookup table is constructed by generating a formula through the lookup table based on a round key, a round function, a random permutation function, and a random vector, a set security condition may also be obtained, and the scale of the lookup table is determined based on the security condition; of course, the set storage condition may also be obtained, and the size of the lookup table may be determined based on the storage condition; it is also possible to acquire a set efficiency condition and determine the size of the lookup table based on the efficiency condition.
It can be understood that, in order to further ensure the security of the white box implementation method provided by the present disclosure, a code obfuscation method may also be used to obfuscate and hide the lookup table in the embodiment of the present disclosure, so as to enhance the difficulty of an attacker in cracking the lookup table, and ensure the security of the entire method.
Referring to fig. 8, fig. 8 is a schematic structural diagram of a white box implementation apparatus according to an exemplary embodiment.
The white box implementing apparatus 800 according to the present disclosure may include:
a first obtaining module 810, configured to obtain data to be processed;
a first determining module 820, configured to determine a first preset number of round operations before and a second preset number of round operations after the Feistel structure-based cipher algorithm as a target round operation;
the first operation module 830 is configured to, when performing target round operation according to a Feistel structure type cipher algorithm, perform round operation on data corresponding to the data to be processed based on a lookup table of the target round operation to obtain a corresponding round operation result, and obtain a processing result of the data to be processed after the Feistel structure type cipher algorithm is performed based on the round operation result;
the first preset number and the second preset number are both greater than or equal to the number of branches of the Feistel structure type cipher algorithm, and the sum of the first preset number and the second preset number is less than or equal to the total round number of the Feistel structure type cipher algorithm; the look-up table comprises a look-up table generated based on the round key and the round function of the target round operation.
The white box realization device that this disclosure relates to can also include:
and the second operation module is used for performing round operation on the data corresponding to the data to be processed based on the round key after mask protection to obtain a corresponding round operation result when performing non-target round operation according to a Feistel structure type cryptographic algorithm, so as to obtain a processing result based on the round operation result.
According to the white box implementation device, the branch number of the Feistel structure type cipher algorithm can include 2;
correspondingly, the method can also comprise the following steps:
the second acquisition module is used for acquiring a key and a round function of the Feistel structure type cipher algorithm before the first operation module performs round operation on data corresponding to the data to be processed based on the lookup table of the target round operation;
the first generation module is used for generating a corresponding round key through a key expansion algorithm based on the key;
the second generation module is used for generating a random permutation function and a random vector;
the first construction module is used for generating a formula construction lookup table through the lookup table based on the round key, the round function, the random permutation function and the random vector;
the look-up table generation formula comprises:
wherein f represents a random permutation function; g represents a random permutation function; k is i A round key representing an ith round of target round operations; f represents a round function of the Feistel structure type cipher algorithm; t is t 1 Representing a first preset number; t is t 2 Representing a second preset number; n represents the total round number of the Feistel structure type cipher algorithm; Δ' represents a random vector; delta i ＝Δ' i-1 ；
Representing an exclusive or operation.
The white box realization device that this disclosure relates to can also include:
the third generation module is used for generating a mask-protected round key through a mask round key generation formula based on a random vector before the first operation module performs round operation on data corresponding to the data to be processed based on the lookup table of the target round operation;
the mask round key generation formula comprises:
wherein, K' i Indicating the mask protected round keys.
The white box implementation apparatus related to the present disclosure, the second operation module may include:
the first operation unit is used for performing round operation on data corresponding to the data to be processed based on the round key after mask protection through a non-target round operation formula to obtain a corresponding round operation result;
the non-target round operation formula comprises:
L' i ＝R′ i-1 、
wherein, L' i Represents the first data to be processed of the (i + 1) th wheel operation, R' i And representing the second data to be processed of the (i + 1) th round operation.
The first determining module may include:
the first determining unit is used for determining first preset number of round operations and second preset number of round operations in front of the Feistel structure type cipher algorithm as target round operations according to preset conditions;
the preset conditions comprise storage safety conditions, storage space conditions and operation efficiency conditions.
The white box realization device that this disclosure relates to can also include:
the second determining module is used for determining the scale of the lookup table according to preset conditions before the first operation module constructs the lookup table through the lookup table generation formula based on the round key, the round function, the random permutation function and the random vector; the preset conditions comprise storage safety conditions, storage space conditions and operation efficiency conditions.
Fig. 9 is a block diagram illustrating an electronic device 900 in accordance with an example embodiment. As shown in fig. 8, the electronic device 900 may include: a processor 901, a memory 902. The electronic device 900 may also include one or more of a multimedia component 903, an input/output (I/O) interface 904, and a communications component 905.
The processor 901 is configured to control the overall operation of the electronic device 900, so as to complete all or part of the steps in the white-box implementation method. The memory 902 is used to store various types of data to support operation of the electronic device 900, such as instructions for any application or method operating on the electronic device 900 and application-related data, such as contact data, messages sent or received, pictures, audio, video, and the like. The Memory 902 may be implemented by any type of volatile or non-volatile Memory device or combination thereof, such as Static Random Access Memory (SRAM), electrically Erasable Programmable Read-Only Memory (EEPROM), erasable Programmable Read-Only Memory (EPROM), programmable Read-Only Memory (PROM), read-Only Memory (ROM), magnetic Memory, flash Memory, magnetic disk or optical disk. The multimedia component 903 may include a screen and an audio component. Wherein the screen may be, for example, a touch screen and the audio component is used for outputting and/or inputting audio signals. For example, the audio component may include a microphone for receiving external audio signals. The received audio signal may further be stored in the memory 902 or transmitted through the communication component 905. The audio assembly further comprises at least one speaker for outputting audio signals. The I/O interface 904 provides an interface between the processor 901 and other interface modules, such as a keyboard, mouse, buttons, etc. These buttons may be virtual buttons or physical buttons. The communication component 905 is used for wired or wireless communication between the electronic device 900 and other devices. Wireless Communication, such as Wi-Fi, bluetooth, near Field Communication (NFC for short), 2G, 3G or 4G, or a combination of one or more of them, and thus the corresponding Communication component 905 may include: wi-Fi module, bluetooth module, NFC module.
In an exemplary embodiment, the electronic Device 900 may be implemented by one or more Application Specific Integrated Circuits (ASICs), digital Signal Processors (DSPs), digital Signal Processing Devices (DSPDs), programmable Logic Devices (PLDs), field Programmable Gate Arrays (FPGAs), controllers, microcontrollers, microprocessors, or other electronic components for performing the white-box implementation method described above.
In another exemplary embodiment, a computer readable storage medium comprising program instructions which, when executed by a processor, implement the steps of the white-box implementation method described above is also provided. For example, the computer readable storage medium may be the above-described memory 902 including program instructions that are executable by the processor 901 of the electronic device 900 to perform the white-box implementation method described above.
For a description of a relevant part in a white box implementation apparatus, an electronic device, and a computer-readable storage medium provided in the embodiments of the present disclosure, reference is made to detailed descriptions of corresponding parts in a white box implementation method provided in the embodiments of the present disclosure, and details are not repeated here. In addition, parts of the above technical solutions provided in the embodiments of the present disclosure that are consistent with the implementation principle of the corresponding technical solutions in the prior art are not described in detail, so as to avoid redundant description.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A white-box implementation method is characterized by comprising the following steps:
acquiring data to be processed;
determining first preset number of round operations before and second preset number of round operations after the Feistel structure type cipher algorithm as target round operations;
when target round operation is carried out according to the Feistel structure type cipher algorithm, round operation is carried out on data corresponding to the data to be processed based on a lookup table of the target round operation to obtain a corresponding round operation result, and a processing result of the data to be processed after the Feistel structure type cipher algorithm operation is carried out is obtained based on the round operation result;
the first preset number and the second preset number are both greater than or equal to the number of branches of the Feistel structure type cipher algorithm, and the sum of the first preset number and the second preset number is less than or equal to the total round number of the Feistel structure type cipher algorithm; the lookup table comprises a lookup table generated based on a round key and a round function of the target round operation;
the construction mode of the lookup table comprises the following steps: acquiring a key and a round function of the Feistel structure type cryptographic algorithm; generating a corresponding round key through a key expansion algorithm based on the key; generating a random permutation function and a random vector; and constructing through a lookup table generation formula based on the round key, the round function, the random permutation function and the random vector.
2. The method of claim 1, further comprising:
when non-target round operation is performed according to the Feistel structure type cipher algorithm, round operation is performed on data corresponding to the data to be processed based on the round key after mask protection to obtain a corresponding round operation result, and the processing result is obtained based on the round operation result.
3. The method of claim 2, wherein the look-up table generating formula comprises:
wherein f represents the random permutation function; g represents the random permutation function; k is i A round key representing an ith round of target round operations; f represents a round function of the Feistel structure type cipher algorithm; t is t 1 Representing the first preset number; t is t 2 Representing the second preset number; n represents the total round number of the Feistel structure type cipher algorithm; Δ' represents the random vector; delta of i ＝Δ' i-1 ；
Representing an exclusive or operation.
4. The method according to claim 3, wherein before performing the round operation on the data corresponding to the data to be processed based on the look-up table of the target round operation, the method further comprises:
generating the mask protected round key through a mask round key generation formula based on the random vector;
the mask round key generation formula comprises:
wherein, K' i Representing the mask protected round keys.
5. The method according to claim 4, wherein performing round operation on data corresponding to the to-be-processed data based on the mask-protected round key to obtain a corresponding round operation result includes:
performing round operation on data corresponding to the data to be processed based on the mask protected round key through a non-target round operation formula to obtain a corresponding round operation result;
the non-target round of operation formula comprises:
wherein, L' i The first data to be processed, R ', representing the i +1 th wheel calculation' i And representing the second data to be processed of the (i + 1) th round operation.
6. The method according to any one of claims 1 to 5, wherein the determining a first preset number of round operations and a second preset number of round operations of the Feistel structure-like cipher algorithm as the target round operations comprises:
determining a first preset number of round operations before and a second preset number of round operations after the Feistel structure type cipher algorithm as the target round operations according to preset conditions;
the preset conditions comprise storage safety conditions, storage space conditions and operation efficiency conditions.
7. The method according to any one of claims 1 to 2, wherein before the constructing the lookup table by the lookup table generation formula based on the round key, the round function, the random permutation function, and the random vector, further comprises:
determining the scale of the lookup table according to a preset condition;
the preset conditions comprise storage safety conditions, storage space conditions and operation efficiency conditions.
8. A white-box implementation apparatus, comprising:
the first acquisition module is used for acquiring data to be processed;
the first determining module is used for determining a first preset number of round operations before and a second preset number of round operations after the first preset number of round operations of the Feistel structure type cipher algorithm as target round operations;
the first operation module is used for performing round operation on data corresponding to the data to be processed based on a lookup table of the target round operation to obtain a corresponding round operation result when the target round operation is performed according to the Feistel structure type cipher algorithm, so as to obtain a processing result of the data to be processed after the Feistel structure type cipher algorithm operation based on the round operation result;
the first preset number and the second preset number are both greater than or equal to the number of branches of the Feistel structure type cipher algorithm, and the sum of the first preset number and the second preset number is less than or equal to the total round number of the Feistel structure type cipher algorithm; the lookup table comprises a lookup table generated based on a round key and a round function of the target round operation; the construction mode of the lookup table comprises the following steps: acquiring a key and a round function of the Feistel structure type cryptographic algorithm; generating a corresponding round key through a key expansion algorithm based on the key; generating a random permutation function and a random vector; and constructing through a lookup table generation formula based on the round key, the round function, the random permutation function and the random vector.
9. An electronic device, comprising:
a memory having a computer program stored thereon;
a processor for executing the computer program in the memory to carry out the steps of the method of any one of claims 1 to 7.
10. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 7.
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