CN116015607A - Method, device and storage medium for operating block cipher algorithm with combined feedback - Google Patents

Abstract

The invention provides a block cipher algorithm working method with combined feedback. When encrypting, the previous plaintext encryption result and the feedback variable generated by the previous encryption process are input into the combined feedback function to obtain the feedback variable required by the current encryption process, and the obtained After the feedback variable is XORed with the current plaintext, encryption is performed to obtain the encrypted ciphertext of the current plaintext; when decrypting, the previous ciphertext and the feedback variable generated by the previous decryption process are input into the combined feedback function to obtain the current decryption process. The feedback variable of the current ciphertext is decrypted, and the result of the decryption process is XORed with the feedback variable to obtain the plaintext after decryption of the current ciphertext; among them, the feedback variable required for the first encryption or decryption is set according to the demand Just set it. The present invention has CPA security and BW‑CPA security based on non-repetitive Nonce, can be implemented in an online manner, and is applied to an online message processing application scenario.

Description

Working method, device and storage medium of block cipher algorithm with combined feedback

technical field

The invention relates to the technical field of communication encryption, in particular to a block cipher algorithm working method, equipment and storage medium with combined feedback.

Background technique

As one of the core algorithms in symmetric ciphers, block cipher algorithm (Block Cipher) has the characteristics of fast encryption and decryption and easy software and hardware implementation. It usually consists of encryption algorithm, decryption algorithm and key generation algorithm. In practical applications, the plaintext that needs to be encrypted is generally not a fixed length or a single data block, and it is necessary to use the block cipher algorithm (Block Cipher Mode of Operation) to encrypt the data in practical applications. The block cipher algorithm working mode is a typical symmetric encryption scheme, including encryption and decryption mode, authentication mode, authentication encryption mode, hash mode, random number generator mode, disk sector encryption mode, key encapsulation mode, and data retention mode etc. By using these algorithm working modes of block ciphers, the block cipher algorithm can be called to process messages of any length, and realize confidentiality, authentication, integrity, random number (or random number sequence) derivation and other cryptographic functions, such as encryption to realize confidentiality mode, the authentication mode to achieve integrity, and the authenticated encryption mode to achieve both confidentiality and integrity, etc.

The working mode of the block cipher algorithm must ensure security while satisfying applicability. For the encryption working mode of the block cipher algorithm, two cases, the conventional attack model and the block-by-block attack model, are mainly considered. Under the conventional chosen-plaintext attack model (Chosen-Plaintext Attack, hereinafter referred to as CPA), the messages processed by the cryptographic scheme are submitted as a whole at one time, but in some actual online applications, the submission and processing of messages are performed one by one. carried out in groups. For example, in real-time applications, due to the randomness of real-time events and the uncertainty of system working status, processing messages cannot be submitted as a whole at one time; or some resource-limited cryptographic devices (such as smart cards), when processing long Its own storage space is limited, and long messages need to be processed in segments. It should be noted that this kind of application scenario of online processing of messages has led to a new type of attack method - packet-by-packet attack. Compared with the conventional attack model, the adversary under the packet-by-packet attack model can control messages to be input in a packet-by-packet manner and get a response in a query process. Taking BlockWise adaptive Chosen-Plaintext Attack (hereinafter referred to as BW-CPA) as an example, the adversary can submit messages group by group when conducting encrypted queries, which is a capability that the adversary does not have under the conventional attack model. The packet-by-packet attack model is closely related to the online implementation of the cryptographic scheme. From the perspective of specific implementation, if the cryptographic scheme cannot resist the packet-by-packet attack, it cannot be applied to the application scenarios of online processing of messages such as real-time systems and resource-constrained devices. .

From the perspective of specific applications, the practicability and security of the existing BC mode are limited. For example, its IV value cannot be used as a Nonce. Although the chain structure of the BC mode has online characteristics, its online implementation is not safe. , and cannot be applied to online message processing application scenarios, etc. Aiming at the fact that the encryption working mode depends on the randomness of the IV value, Rogaway adopts the idea of using two keys, one of which is used to encrypt the Nonce value first, and the obtained ciphertext is used as the initial value of the feedback variable (The Feedback) The other key is used as the encryption key for plaintext message processing. Such transformation makes the operating efficiency of the mode close to the original mode, but the method requires a large amount of keys and cannot resist BW-CPA. Aiming at the problem of being unable to resist BW-CPA, Fouque et al. proposed a general method - delaying the ciphertext output by one packet, and proved that it can resist BW-CPA. However, the security of the new mode obtained by this method still depends on the randomness of the IV value, and may reduce the response efficiency of the application system.

Contents of the invention

Aiming at the problems existing in the prior art, a block cipher algorithm working method, equipment and storage medium with combined feedback are provided, the BC encryption mode is improved, and the security enhancement design based on encryption Nonce, XE structure and combined feedback Function and other strategies and design methods, lightweight design is carried out for the existing CbF combined feedback function without reducing safety.

The technical scheme that the present invention adopts is as follows: the block cipher algorithm working method of band combination feedback,

When encrypting, the previous plaintext encryption result and the feedback variable generated by the previous encryption process are input into the combined feedback function to obtain the feedback variable required by the current encryption process, and the obtained feedback variable is XORed with the current plaintext and then encrypted to obtain The ciphertext after encrypting the current plaintext;

When decrypting, the previous ciphertext and the feedback variable generated by the previous decryption process are input into the combined feedback function to obtain the feedback variable required by the current decryption process, and the current ciphertext is decrypted, and the result obtained by the decryption process is compared with the feedback variable. XOR operation to obtain the plaintext after decryption of the current ciphertext;

The feedback variables required for the first encryption or decryption can be set according to requirements.

Further, the combined feedback function is ρ(F, C)=(I ₁ , I ₂ ), where F is the input feedback variable, C is the input ciphertext, and I ₁ is the XOR operation with the plaintext Feedback variable, I ₂ is used for the feedback variable of next encryption or decryption process input combination feedback function;

For I ₁ ∈ {0, 1} ⁿ , I ₂ ∈ {0, 1} ⁿ , the specific operation of the combined feedback function ρ(F, C)=(I ₁ , I ₂ ) is:

均为双射，特殊的运算实例为：令W＝(w₀||w₁||…||…w_n-1)∈{0，1}ⁿ，则Among them, the function S(W) satisfies W→S(W) and

Both are bijective, and the special operation example is: let W=(w ₀ ||w ₁ ||…||…w _n-1 )∈{0, 1} ⁿ , then

Further, the encryption process is specifically:

Step 1. Set the initial feedback variables FB ₁ and F ₁ to encrypt the plaintext P _i , i=1...m; the initial value of i is 1;

Step 2. Execute XOR processing on the feedback variable FB _i and the plaintext P _i , and then encrypt to obtain the encrypted result C _i ;

Step 3. If i<m, input the encryption result C _i and the feedback variable F _i+1 into the combined feedback function to obtain the next encryption process feedback variables FB _i+1 and F _i+1 , and add 1 to the value of i; Otherwise, output the encryption result directly; repeat steps 2-3 to get all plaintext encryption results.

Further, the decryption process is specifically:

Step 1. Set the initial feedback variables FB ₁ and F ₁ to decrypt the plaintext Ci, i=1...m; the initial value of i is 1;

Step 2. Decrypt the ciphertext C _i , and XOR the decryption result with the feedback variable FB _i to obtain the plaintext;

Step 3. If i<m, input the ciphertext C _i and the feedback variable F _i into the combined feedback function to obtain the feedback variables FB _i+1 and F _i+1 in the next decryption process, and add 1 to the value of i; otherwise, directly output Encrypted results; repeat steps 2-3 to get all plaintext.

Further, the combined feedback function of the encryption and decryption process is specifically:

为输出的反馈变量FB_i+1，

为输出的反馈变量F_i+1。Among them, ρ is a combined feedback function, F _i is an input feedback variable, and C _i is an input encryption result;

is the output feedback variable FB _i+1 ,

is the output feedback variable F _i+1 .

The present invention also proposes an electronic device, including a memory and a processor, and the memory stores a computer program that can be loaded by the processor and execute the working method of the block cipher algorithm with combined feedback as described above.

The present invention also proposes a computer-readable storage medium on which computer program instructions are stored, wherein, when the program instructions are executed by a processor, they are used to implement the process corresponding to the above-mentioned block cipher algorithm working method with combined feedback.

Compared with the prior art, the beneficial effect of adopting the above technical solution is: the present invention has CPA security and BW-CPA security based on non-repetitive Nonce, is not easy to be misused, and has the option of selecting plaintext in concurrent group-by-group adaptation Confidentiality under attack can be realized online and applied to online message processing application scenarios. In addition, based on the combined feedback function, the feedback link form of the new algorithm working mode is designed, and the security enhancement design of the existing algorithm working mode is carried out, which also provides a new design idea for the safe application of the algorithm working mode.

Description of drawings

Fig. 1 is a schematic diagram of the working method of the block cipher algorithm with combined feedback proposed by the present invention.

Detailed ways

Embodiments of the present application are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar modules or modules having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary, are only for explaining the present application, and should not be construed as limiting the present application. On the contrary, the embodiments of the present application include all changes, modifications and equivalents falling within the spirit and scope of the appended claims.

Example 1

From the perspective of specific applications, the practicability and security of the BC mode are limited, and its online implementation is unsafe and cannot be applied to online message processing application scenarios. At the same time, by analyzing the existing potential improvement methods and their technical routes, it is found that directly applying the existing improvement methods cannot simultaneously solve the two key problems of Nonce-based security and resistance to BW-CPA.

In response to these problems, this embodiment improves the BC encryption mode, based on strategies and design methods such as security enhancement design of encryption Nonce, XE structure and combination feedback function, and implements the existing CbF combination feedback function without reducing security. In order to improve the lightweight design, a new type of CbF combined feedback function design method is proposed, which is easy to realize by software and hardware and has low software and hardware computing overhead. In order to ensure the efficiency of the algorithm, the combined feedback function CbF should not be designed too complicated. Try to use some simple operation logic, such as XOR, shift, etc. In addition, the calculation of CbF should not add additional storage, so that the implementation cost can be as small as possible. Based on this, this embodiment proposes a block cipher algorithm working method with combined feedback, as shown in Figure 1, specifically as follows:

When encrypting, the previous plaintext encryption result and the feedback variable generated by the previous encryption process are input into the combined feedback function to obtain the feedback variable required by the current encryption process, and the obtained feedback variable is XORed with the current plaintext and then encrypted to obtain The ciphertext after encrypting the current plaintext;

When decrypting, the previous ciphertext and the feedback variable generated by the previous decryption process are input into the combined feedback function to obtain the feedback variable required by the current decryption process, and the current ciphertext is decrypted, and the result obtained by the decryption process is compared with the feedback variable. XOR operation to obtain the plaintext after decryption of the current ciphertext;

The feedback variables required for the first encryption or decryption can be set according to requirements.

The working method of the block cipher algorithm with combined feedback is expressed in the Cb_BC mode in this embodiment, which has CPA security and BW-CPA security based on non-repeating Nonce. A sequence composed of variables FB, which is used to XOR with plaintext variables.

In this embodiment, the Cb_BC mode uses the security enhancement design and XE structure based on encryption Nonce, and replaces the XOR operation of the ciphertext and the feedback variable in the original BC mode with the combined feedback function ρ(F, C)=( I ₁ , I ₂ ), where I ₁ replaces the original feedback value F as a new feedback value and XORs with the plaintext P, I ₂ replaces the original feedback value F and performs XOR with the ciphertext C, I ₁ and I ₂ Feedback positions can be swapped as required.

Here, the combined feedback function ρ(F, C) is further explained:

For I ₁ ∈ {0, 1} ⁿ , I ₂ ∈ {0, 1} ⁿ , the specific operation of the combined feedback function ρ(F, C)=(I ₁ , I ₂ ) is:

均为双射，特殊的运算实例为：令W＝(w₀||w₁||…||w_n-1)∈{0，1}ⁿ，则Among them, the function S(W) satisfies W→S(W) and

Both are bijective, and the special operation example is: Let W=(w ₀ ||w ₁ ||…||w _n-1 )∈{0, 1} ⁿ , then

比特异或减少至1比特异或，大大减少了组合反馈函数的硬件实现代价，达到了保证安全性质要求情况下算法硬件实现的异或逻辑资源最小化。The combined feedback function proposed in this embodiment will be in S(W)

The bit XOR is reduced to 1 bit XOR, which greatly reduces the hardware implementation cost of the combined feedback function, and achieves the minimum XOR logic resources implemented by the algorithm hardware under the condition of ensuring the safety property.

Further, taking I ₁ as the XOR feedback value with the plaintext and I ₂ as the XOR feedback value with the ciphertext as an example, the encryption and decryption methods of the Cb_BC mode will be described in detail:

The encryption process of Cb_BC mode is:

1. Set the initial values of feedback variables F ₁ and FB ₁ to IV: F ₁ =FB ₁ =IV;

2. FOR(i=1; i≤m; i++)

{

(1) Encrypt the XOR value of FB _i and plaintext P _i to obtain the ciphertext:

(2) Take the ciphertext C _i and F _i as the input of the feedback function ρ:

(3) IF(i<m):

分别作为下一轮反馈初始值FB_i+1、F_i+1：Will

As the initial values FB _i+1 and F _i+1 of the next round of feedback respectively:

}

3. Obtain all ciphertexts C ₁ , C ₂ , . . . , C _m .

The decryption process of Cb_BC mode is:

1. Set the initial values of feedback variables F ₁ and FB ₁ to IV: F ₁ =FB ₁ =IV;

2. FOR(i=1; i≤m; i++)

{

将其与FB_i异或得到明文P_i：(1) Decrypt the ciphertext C _i :

XOR it with FB _i to get the plaintext P _i :

(2) Take the ciphertext C _i and F _i as the input of the feedback function ρ:

(3) IF(i<m):

分别作为下一轮反馈初始值FB_i+1、F_i+1：Will

As the initial values FB _i+1 and F _i+1 of the next round of feedback respectively:

3. Obtain all plaintexts P ₁ , P ₂ , ..., P _m .

It should be noted that, in this embodiment, the encryption process corresponds to the decryption process, and the feedback variables F and FB in the encryption process are correspondingly the same as the feedback variables F and FB in the decryption process.

This embodiment improves the design of the traditional BC encryption mode, based on strategies and design methods such as the security enhancement design of the encryption Nonce, the XE structure, and the combined feedback function, and performs a light modification of the existing CbF combined feedback function without reducing security. Quantitative design, easy software and hardware implementation and low software and hardware computing overhead, get the encryption and decryption working mode Cb_BC based on the block cipher algorithm with combined feedback function design, which enhances its security and expands the application flexibility and scope of application.

The Cb_BC mode has CPA security and BW-CPA security based on non-repeating Nonce, so Cb_BC is not easy to be misused, and has confidentiality under concurrent group-by-group adaptive chosen plaintext attacks, which can be implemented online and applied to Online message processing application scenarios. In addition, based on the combined feedback function, the feedback link form of the new algorithm working mode is designed, and the security enhancement design of the existing algorithm working mode is carried out, which also provides a new design idea for the safe application of the algorithm working mode.

Example 2

This embodiment also proposes an electronic device, including a memory and a processor, and the memory stores a computer program that can be loaded by the processor and execute the working method of the block cipher algorithm with combined feedback described in Embodiment 1.

Example 3

The present invention also proposes a computer-readable storage medium on which computer program instructions are stored, wherein, when the program instructions are executed by a processor, they are used to implement the working method of the block cipher algorithm with combined feedback described in Embodiment 1 corresponding process.

It should be noted that, in the description of the embodiments of the present invention, unless otherwise specified and limited, the terms "setting" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection, or integrally connected; it may be directly connected or indirectly connected through an intermediary. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations; the drawings in the embodiments are used to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the The described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limitations on the present application, and those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (7)

1. the block cipher algorithm working method of band combination feedback, it is characterized in that, When encrypting, the previous plaintext encryption result and the feedback variable generated by the previous encryption process are input into the combined feedback function to obtain the feedback variable required by the current encryption process, and the obtained feedback variable is XORed with the current plaintext and then encrypted to obtain The ciphertext after encrypting the current plaintext; When decrypting, the previous ciphertext and the feedback variable generated by the previous decryption process are input into the combined feedback function to obtain the feedback variable required by the current decryption process, and the current ciphertext is decrypted, and the result obtained by the decryption process is compared with the feedback variable. XOR operation to obtain the plaintext after decryption of the current ciphertext; Wherein, the feedback variable required for the first encryption or decryption can be set according to requirements. 2. the block cipher algorithm working method of band combination feedback according to claim 1, is characterized in that, described combination feedback function is ρ (F, C)=(I ₁ , I ₂ ), wherein F is the feedback of input Variable, C is the ciphertext of input, I ₁ is used for the feedback variable of XOR operation with plaintext, I ₂ is used for the feedback variable of next encryption or decryption process input combination feedback function; For I ₁ ∈{0,1} ⁿ , I ₂ ∈{0,1} ⁿ , the specific operation of the combined feedback function ρ(F,C)=(I ₁ ,I ₂ ) is:

Among them, the function S(W) satisfies W→S(W) and

Both are bijective, and the special operation example is: let W=(w ₀ ||w ₁ ||…||w _n-1 )∈{0,1} ⁿ , then

3. the block cipher algorithm work method with combination feedback according to claim 2, is characterized in that, encryption process is specifically: Step 1. Set the initial feedback variables FB ₁ and F ₁ to encrypt the plaintext P _i , i=1...m; the initial value of i is 1; Step 2. Execute XOR processing on the feedback variable FB _i and the plaintext P _i , and then encrypt to obtain the encrypted result C _i ; Step 3. If i<m, input the encryption result C _i and the feedback variable F _i+1 into the combined feedback function to obtain the next encryption process feedback variables FB _i+1 and F _i+1 , and add 1 to the value of i; Otherwise, output the encryption result directly; repeat steps 2-3 to get all plaintext encryption results. 4. the block cipher algorithm work method of band combined feedback according to claim 3, is characterized in that, deciphering process is specifically: Step 1. Set the initial feedback variables FB ₁ and F ₁ to decrypt the plaintext Ci, i=1...m; the initial value of i is 1; Step 2. Decrypt the ciphertext C _i , and XOR the decryption result with the feedback variable FB _i to obtain the plaintext; Step 3. If i<m, input the ciphertext C _i and the feedback variable F _i into the combined feedback function to obtain the feedback variables FB _i+1 and F _i+1 in the next decryption process, and add 1 to the value of i; otherwise, directly output Encrypted results; repeat steps 2-3 to get all plaintext. 5. the block cipher algorithm work method with combination feedback according to claim 4, is characterized in that, encryption and decryption process combination feedback function is specifically:

Among them, ρ is a combined feedback function, F _i is an input feedback variable, and C _i is an input encryption result;

is the output feedback variable FB _i+1 ,

is the output feedback variable F _i+1 . 6. An electronic device, characterized in that it comprises a memory and a processor, the memory is stored with a block cipher algorithm that can be loaded by the processor and executed as described in any one of claims 1 to 5 with combined feedback The computer program corresponding to the working method. 7. A computer-readable storage medium on which computer program instructions are stored, wherein the program instructions are used to implement the block cipher with combined feedback according to any one of claims 1 to 5 when executed by a processor The process corresponding to the algorithm working method.

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