CN107204841A - A kind of method that many S boxes of the block cipher for resisting differential power attack are realized - Google Patents

Abstract

The present invention relates to a block cipher multi-S-box implementation method for resisting differential power consumption attacks. First, multiple parallel S-boxes are converted to obtain 4×4S-box replacements, and the 4×4S-box replacements are numbered, and then all The 4×4S box replacement of block cipher multi-S box randomized input technology makes it impossible for the attacker of the differential power consumption attack to align the curve according to the relevant statistical difference method after obtaining the power consumption curve, which leads to the failure of the differential power consumption attack and improves the The security achieved by the block cipher is improved, and this scheme only uses g(n) bits of random numbers, which is much reduced compared to other masking schemes; it greatly improves the attack difficulty of differential power consumption attacks in data processing; the speed On the one hand, since this scheme transforms the original parallel S-box into a multi-dimensional serial reusable S-box framework, the pipeline method can be adopted to reduce the speed by 30% compared with the original scheme.

Description

A Multi-S-box Implementation Method of Block Cipher Against Differential Power Attack

technical field

The invention relates to the technical field of side channel attack and defense theory in an information security system, and in particular relates to a block cipher multi-S-box implementation method for resisting differential power consumption attacks.

Background technique

Differential power consumption attack is a physical attack on cryptographic chips first proposed by American expert Paul Kocher in 1999. This scheme first collects the power consumption generated by the chip when running the block cipher algorithm, and then uses the correlation between power consumption and key data to In order to recover the key, the method of statistical difference is used. Because of its advantages of high efficiency and low cost, it has brought great threats and challenges to the security of information security systems. Its related theories have been developed for nearly 20 years, and it is still a hot spot for experts to study.

With the maturity of differential power attack theory, many defense schemes have emerged. Two of them are more popular. The first one is random masking technology, which inserts appropriate random numbers into the cryptographic algorithm, and randomizes the key data of the target in the differential power attack without changing the encryption and decryption results. XOR operation, so that the power consumption corresponding to the key data is changed to achieve the purpose of protecting the key; the second is to introduce noise technology, which is to artificially add noise in the cryptographic algorithm circuit, so that the attacker uses differential power consumption to attack The efficiency is reduced, and even the key cannot be recovered, so as to achieve the purpose of protecting the key.

However, the above two technologies have a common drawback, that is, significantly increasing the resources consumed by the hardware or reducing the computing speed, which seriously restricts the development of security chips. Since the S-box is the only non-linear component in the block cipher, the resources consumed after its implementation account for 50%-70% of the total resources. At the same time, because its non-linearity is also the reason for the leakage of sensitive information in the power attack, so How to effectively protect the S-box is the focus of research on defense against differential power attacks in recent years.

Contents of the invention

The purpose of the present invention is to provide a block cipher multi-S-box realization method against differential power consumption attack, so as to improve S-boxes and realize effective protection.

For this reason, the present invention provides a kind of block cipher multi-S box realization method that resists differential power consumption attack, it is characterized in that, comprises the steps:

Step 1: Select a block cipher algorithm, convert multiple parallel S-boxes to obtain n 4×4 S-box permutations, and number the 4×4 S-box permutations from 0 to n-1;

The specific operation steps are:

A. Convert n independent parallel S-boxes into a multi-dimensional serial reusable S-box framework S′ through compression algorithm,

B. Number the 4×4 S-box permutations in S′, that is

Among them, m _n-1 represents the input of the n-1 4-bit S-box permutation, S _n-1 (m _n-1 ) represents the output of the n-1 4-bit S-box permutation, and S′ represents the multidimensional serial Reusable S-box framework.

Step 2: Perform S-box operation to generate a random number, and select the 4×4 S-box corresponding to the random number to replace;

The specific operation steps are:

1) Before the circuit performs the S-box operation, a random number R ₁ is generated, namely

R ₁ =(r ₁ ,r ₂ ,...r _g(n) ) (2)

Wherein, 0≤R 1≤n- ₁ , g(n) represents the number of binary bits corresponding to the number n of 4×4 S-boxes actually participating in the operation;

2) According to the value of R ₁ , select the corresponding 4×4 S-box permutation into S′, that is, the permutation is in Indicates the result of 4 × 4 S-box permutation.

Step 3: Generate the next random number through the random number update algorithm, and select the 4×4S box replacement corresponding to the random number;

That is: the random number R ₁ is XORed with the output of the selected first 4×4 S-box replacement entering S′, and the obtained result is used as the random number R ₂ for selecting the next 4×4 S-box replacement, which is

Step 4: Repeat Step 3. If it is found that the 4×4 S-box replacement corresponding to the newly generated random number has been selected, then perform an XOR operation on the newly generated random number bit by bit to obtain a 1-bit number;

The specific operation steps are:

a) Repeat step 3. If it is found that the 4×4 S box permutation corresponding to the newly generated random number R _i has been selected, then perform step b) until the 4×4 S box corresponding to the newly generated random number R _i is found. until box replacement is not selected;

b) Execute the XOR operation on R _i bit by bit to get R _i ^* , that is

Step 5: Select the distinguishing function, re-select the next 4×4 S-box replacement, if it is still the 4×4 S-box replacement that has been selected, continue to step 5 until the found 4×4 S-box replacement is the one not previously selected. Selected and skip back to step 3;

The specific operation is: choose a distinguishing function f(R _i ^* )

If the result of the XOR operation on R _i bit by bit, R _i ^* is "0", select the replacement When R _i ^* is "1", the replacement is selected If the selected 4×4 S-box replacement is still selected, continue to perform this step until the found 4×4 S-box replacement is a replacement that has not been selected before.

Step 6: Repeat steps 3 to 5 until all 4×4 S box replacements are selected.

Beneficial effects of the present invention: the block cipher multi-S box implementation method for resisting differential power consumption attacks provided by the present invention occupies the same resources as the method provided by the prior art for resisting differential power consumption attacks, and consumes resources only increasing the total 3% of resources, but only a random number of g(n) bits is used, which is much reduced compared to other masking schemes, and greatly improves the attack difficulty of differential power consumption attacks in data processing; since the distinguishing function f( The randomness of R _i ^* ) makes the length of the power consumption curve of the attacker to obtain the key data of the S box different each time, thus greatly increasing the difficulty of aligning the power consumption data in the later stage of DPA.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is a flow chart of the calculation process of the block cipher multi-S box implementation method against differential power consumption attack.

Fig. 2 Schematic diagram of multi-dimensional serial reusable S-box framework S'.

Figure 3 Registers corresponding to Sbox.

Figure 4 Internal structure of Reg.

Figure 5 The internal structure of the flip-flop.

detailed description

In order to further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific implementation, structural features and effects of the present invention will be described in detail below in conjunction with the accompanying drawings and examples.

Example 1

In order to improve the effective protection of the S-boxes, the present invention provides a block cipher multi-S-box implementation method for resisting differential power consumption attacks as shown in FIG. A three-level register is added in the middle of the box frame, so that the speed of cryptographic operations will not drop too much compared with the original scheme, and the efficiency is improved.

Using the block cipher multi-S-box randomized input technology, the attacker of the differential power consumption attack cannot align the curve according to the relevant statistical difference method after obtaining the power consumption curve, thus resulting in the failure of the differential power consumption attack and improving the security of the block cipher implementation sex.

The specific plan includes the following steps:

Step 1: Select a block cipher algorithm, convert multiple parallel S-boxes to obtain 4×4 S-box permutations, and number the 4×4 S-box permutations from 0 to n-1 (change here, according to According to Nikova's theory, when the number of input bits n≥4, such a permutation is safe, and we noticed that in the current cryptographic scheme, the smallest S-box is also 4×4 in size, so this scheme It is logical to assume that the smallest permutation in the resulting S-box frame is 4×4);

The specific operation steps are:

A. Convert n independent parallel S-boxes into a multi-dimensional serial reusable S-box framework S′ through compression algorithm,

B. Number the 4×4 S-box permutations in S′, that is

Among them, m _n-1 represents the input of the n-1 4-bit S-box permutation, S _n-1 (m _n-1 ) represents the output of the n-1 4-bit S-box permutation, and S′ represents the multidimensional serial Reusable S-box framework.

Step 2: The circuit performs the S-box operation to generate a random number. The value range of the random number is within the numbering range of the 4×4 S-box replacement, and select the 4×4 S-box replacement corresponding to the random number;

The specific operation steps are:

1) Before the circuit performs the S-box operation, a random number R ₁ is generated, namely

R ₁ =(r ₁ ,r ₂ ,...r _g(n) ) (2)

Wherein, 0≤R 1≤n- ₁ , g(n) represents the number of binary bits corresponding to the number n of 4×4 S-boxes actually participating in the operation;

2) According to the value of R ₁ , select the corresponding 4×4 S-box permutation into S′, that is, the permutation is in Indicates the result of 4 × 4 S-box permutation.

Step 3: Generate the next random number through the random number update algorithm, and select the 4×4S box replacement corresponding to the random number;

That is: the random number R ₁ is XORed with the output of the selected first 4×4 S-box replacement entering S′, and the obtained result is used as the random number R ₂ for selecting the next 4×4 S-box replacement, which is

Step 4: Repeat Step 3. If it is found that the 4×4 S-box replacement corresponding to the newly generated random number has been selected, then perform an XOR operation on the newly generated random number bit by bit to obtain a 1-bit number;

The specific operation steps are:

a) Repeat step 3. If it is found that the 4×4 S box permutation corresponding to the newly generated random number R _i has been selected, then perform step b) until the 4×4 S box corresponding to the newly generated random number R _i is found. until box replacement is not selected;

b) Execute the XOR operation on R _i bit by bit to get R _i ^* , that is

Step 5: Select the distinguishing function, re-select the next 4×4 S-box replacement, if it is still the 4×4 S-box replacement that has been selected, continue to step 5 until the found 4×4 S-box replacement is the one not previously selected. Selected and skip back to step 3;

The specific operation is: choose a distinguishing function f(R _i ^* )

If the result of the XOR operation on R _i bit by bit, R _i ^* is "0", select the replacement When R _i ^* is "1", the replacement is selected If the selected 4×4 S-box replacement is still selected, continue to perform this step until the found 4×4 S-box replacement is a replacement that has not been selected before.

Step 6: Repeat steps 3 to 5 until all 4×4 S box replacements are selected.

This block cipher multi-S-box implementation method for resisting differential power consumption attacks has the following advantages:

(1) This scheme only uses a random number of g(n) bits, which is much reduced compared to other masking schemes.

(2) Due to the randomness of the distinguishing function f(R _i ^* ), the length of the power consumption curve of each time the attacker obtains the key data of the S box is different, which greatly increases the difficulty of aligning the power consumption data in the later stage of DPA.

(3) In terms of resources, whether this solution is implemented based on a lookup table or a logic gate, compared with the original implementation, the resource consumption will not increase much.

(4) In terms of speed, since this scheme converts the original parallel S-boxes into serial S-boxes, the PIPELINE method can be used, so that the speed will not decrease much compared to the original scheme.

Example 2

Taking the block cipher algorithm DES as an example, the present invention is further described in detail.

Although we know that the DES algorithm of the 56bit key has been proved to be insecure in many applications. But we know that Triple-DES is still widely used in the field of electronic payment, because it has a key of 112bits, so it is proved to be safe.

The DES algorithm is a symmetric cryptosystem in the cryptographic system, also known as the American Data Encryption Standard. It is a symmetric cryptosystem encryption algorithm developed by IBM Corporation in the United States in 1972. The plaintext is grouped by 64 bits, the key length is 64 bits, and the key is actually 56 bits to participate in the DES operation (the 8th, 16th, 24th, 32nd, 40th, 48th, 56th, and 64th bits are check bits, so that each key All keys have an odd number of 1) grouped plaintext groups and 56-bit keys that are replaced or exchanged bit by bit to form an encryption method for a ciphertext group.

According to the content of the DES algorithm, its S box is composed of eight 6×4 S boxes in parallel, and the 1st and 6th bits of its 6-bit input in each S box are used to determine its 2nd to 6th bits. A 4-bit input consisting of 5 bits goes into which of the 4 4x4 permutations. Therefore, actually 8 6×4 S-boxes are composed of 32 4×4 S-boxes. We implement the DES algorithm S-box according to the process in the scheme. The specific steps are as follows:

1. Convert 8 6×4 S-boxes in the DES algorithm into 32 4×4 S-boxes, and use Bilgin’s multiplexing idea to convert n independent parallel S-boxes into a multi-dimensional serial reusable through compression algorithm The converted logic diagram of the S-box frame S′ is shown in Figure 2, where GK, GL, F, A ^ij , B ^ij , and C ^ij are known permutations, and the specific permutations refer to [1].

2. Since there are 8 4×4 S-boxes actually participating in the DES algorithm S-box operation, so n=8, then g(n)=3. In order to meet the subsequent algorithm requirements, we make a correction to g(n).

Let g(n)′=g(n)+1=4, so the generated random number R ₁ =(r ₁ ,r ₂ ,…r _g(n)′ )=(r ₁ ,r ₂ ,r ₃ , r ₄ ), 0≤R ₁ ≤15.

3. Set R ₁ ′=(r ₂ , r ₃ , r ₄ ), select the first 4×4 S box that enters S′ to be replaced by the value of R ₁ ′, that is, the replacement is

4. XOR the random number R ₁ with the output of the selected first 4×4 S-box replacement entering S′, and the obtained result is used as the random number for selecting the next 4×4 S-box replacement.

5. Repeat steps 3 and 4. If it is found that the 4×4 S-box permutation corresponding to the newly generated random number R _i has already been selected, then perform step 6.

6. Perform an exclusive OR operation on R _i bit by bit to obtain R _i ^* . which is

7. Choose a distinguishing function f(R _i ^* )

If the result of the XOR operation on R _i bit by bit, R _i ^* is "0", select the replacement When it is "1", the replacement is selected If the selected 4×4 S-box replacement is still selected, continue to perform this step until the found 4×4 S-box replacement is an unselected replacement and return to step 3.

8. Repeat the above steps until all 8 4×4 S-box replacements are selected and enter the multi-dimensional serial reusable S-box framework.

Finally, the security of the scheme of the present invention is described.

Security analysis of this program

Theory of Power Analysis

The target of the DPA power consumption attack is the output of the register corresponding to the S box in the cryptographic algorithm circuit. Taking 4×4Sbox as an example, the figure is a specific circuit diagram, and the power region in Figure 3 is the area where the attacker wants to collect power consumption. .

This area is composed of four 1-bit registers, and each reg corresponds to the output of a bit Sbox. The internal structure of reg is shown in Figure 4.

One of the regs is composed of a small number of control devices and a D flip-flop, as shown in Figure 5, and the D flip-flop is composed of 6 NAND gates.

Therefore, when the input D jumps, there will be about 8 AND gates, 1 OR gate and 1 NOT gate internal CMOS transistors to generate instantaneous dynamic power consumption, and the attacker can use DPA to detect the power consumption based on the collected power consumption. The device is attacked.

This scheme adopts the technology of randomly inputting 4×4 S-boxes, so that in the framework of multi-dimensional serial reusable S-boxes, it is possible to recover the correct key only when the key and the random number must be guessed at the same time. The possibility of guessing the key data and power consumption value corresponding to the key and the random number is shown in Table 1.

guess the key guess random number key data power consumption Possibility 1 correct correct can be determined can be determined Possibility 2 correct mistake random random Possibility 3 mistake correct random random Possibility 4 mistake mistake random randomly

Table 1

Next calculate the probability of an attacker recovering the key. The probability of guessing a set of keys is: 1/16, and the probability of guessing a 4×4S box is: 1/8. In the differential power attack, the attacker chooses n groups of plaintext.

The possibility of analyzing the key corresponding to the i-th group of 4×4 S-boxes is no more than (1/2) ³⁽ⁿ⁺⁴⁾ .

Since the value of n is generally between 1000 and 2000 in differential power consumption attacks, it can be seen that only when the attacker guesses the key and the random number at the same time can it be possible to confirm the correct key. However, in the later data processing, since the present invention uses the discrimination function f(R _i ^* ), it is very difficult for an attacker to align all target curves.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

[1] Bilgin B, Knezevic M, Nikov V, et al.Compact Implementations of Multi-Sbox Designs[C]//International Conference on Smart Card Research and Advanced Applications. Springer International Publishing, 2015:273-285.

Claims (6)

1. a kind of method that many S boxes of the block cipher for resisting differential power attack are realized, it is characterised in that comprise the following steps：

Step one：A kind of block cipher is selected, multiple parallel S boxes are changed, n 4 × 4S boxes displacements are obtained, and it is right The displacement of 4 × 4S boxes carries out 0 to n-1 and numbered；

Step 2：S box computings are carried out, a random number are produced, and select the corresponding 4 × 4S boxes displacement of random number；

Step 3：Next random number is produced by random number more new algorithm, and selects 4 × 4S boxes corresponding with the random number to put Change；

Step 4：Repeat step three, if finding, 4 × 4S boxes corresponding to newly-generated random number replace chosen mistake, then By newly-generated random number, xor operation is carried out by turn, obtains 1 bit number；

Step 5：Selective discrimination function, reselects next 4 × 4S boxes displacement, if being still 4 × 4S boxes of chosen mistake Displacement, then continue executing with step 5, non-selected mistake and rebound step 3 before the 4 × 4S boxes displacement found is；

Step 6：Repeat step three is to step 5, until the displacement of all 4 × 4S boxes all selects the beam that finishes.

2. a kind of method that many S boxes of the block cipher for resisting differential power attack are realized, it is characterised in that the step one is specific Operating procedure is：

A, the S boxes of n independent parallel are converted into by the serial reusable S box frameworks S ' of a multidimensional by compression algorithm,

B, in S ' 4 × 4S boxes displacement be numbered, i.e.,

Wherein, m_n-1Represent the input of (n-1)th 4 bit S boxes displacement, S_n-1(m_n-1) represent what (n-1)th 4 bit S box was replaced Output, S ' represents the serial reusable S box frameworks of multidimensional.

3. the method that a kind of new many S boxes of the block cipher for resisting differential power attack according to claim 1 are realized, its It is characterised by, the step 2 comprises the following steps：

1) carry out before S box computings, produce a random number R₁, i.e.,

R₁=(r₁,r₂,…r_g(n)) (2)

Wherein, 0≤R₁≤ n-1, g (n) represent 2 system number of bits corresponding to the number n of actual participation computing 4 × 4S boxes；

2) R is passed through₁Value select corresponding entrance S ' 4 × 4S boxes displacement, i.e., this is replaced intoWhereinRepresent 4 × 4S boxes The result of displacement.

4. the method that a kind of new many S boxes of the block cipher for resisting differential power attack according to claim 1 are realized, its It is characterised by, the step 3 concrete operations are：

By random number R₁Xor operation is carried out with the output that the selected first 4 × 4S box for entering S ' is replaced, obtained result is made To select the random number R of next 4 × 4S boxes displacement₂, i.e.,

5. the method that a kind of new many S boxes of the block cipher for resisting differential power attack according to claim 1 are realized, its It is characterised by, the step 4 comprises the following steps：

A) repeat step three, if finding newly-generated random number R_iCorresponding 4 × 4S boxes replace chosen mistake, then perform Step b), until now newly-generated random number R_iUntill corresponding 4 × 4S boxes replace not selected mistake；

B) by R_iXor operation is carried out by turn, obtains R_i ^*, i.e.,

6. the method that a kind of new many S boxes of the block cipher for resisting differential power attack according to claim 1 are realized, Characterized in that, the concrete operations of the step 5 are：Select a distinguishing funotion f (R_i ^*)

If R_iThe result R of xor operation is carried out by turn_i ^*During for " 0 ", then selection displacementR_i ^*Then selected during for " 1 " DisplacementIf being still 4 × 4S boxes displacement of chosen mistake after selection, this step is continued executing with, until finding 4 × 4S boxes displacement be before non-selected mistake displacement.