CN115544551B

CN115544551B - Data encryption method for MCU singlechip operating system

Info

Publication number: CN115544551B
Application number: CN202211495804.4A
Authority: CN
Inventors: 艾亮东
Original assignee: Beijing Sizhong Electronic Technology Co ltd
Current assignee: Beijing Sizhong Electronic Technology Co ltd
Priority date: 2022-11-28
Filing date: 2022-11-28
Publication date: 2023-02-21
Anticipated expiration: 2042-11-28
Also published as: CN115544551A

Abstract

The invention relates to the technical field of data processing, in particular to a data encryption method of an MCU singlechip operating system, which comprises the following steps: the letter matrix is partitioned, a second candidate letter and a first letter combination are obtained according to the frequency of each letter in each partitioned letter matrix, total runlength and larger total frequency are further obtained, large-run disorder and small-run disorder are carried out according to the larger total frequency predicted by the total runlength, and an alphanumeric mapping table is obtained; each letter in the block letter matrix is chain encrypted according to the alphanumeric mapping table and the alternative letter sequence of each letter. The method has the advantages of large disorder among ciphertexts, large difficulty in breaking, simple encryption method and small calculation amount, and ensures the safety of program code storage.

Description

Data encryption method for MCU singlechip operating system

Technical Field

The invention relates to the technical field of data processing, in particular to a data encryption method of an MCU singlechip operating system.

Background

The method is characterized in that a program code is encrypted through a password, so that the program is changed into a ciphertext, and the method is a common MCU encryption mode. However, such protection measures are fragile and easy to crack, and an attacker of the single chip microcomputer can extract key information from the chip by using bugs or software defects on the design of the single chip microcomputer chip through various technical means by means of special equipment or self-made equipment to obtain the program in the single chip microcomputer.

Based on the above, the invention provides a data encryption method of an MCU singlechip operating system, which combines the letter probability in plain text to perform self-adaptive setting on an alphanumeric mapping table in the encryption process, on one hand, the encryption method is simple and has small calculation amount, and on the other hand, the difference between the encrypted ciphertext and the original plaintext is large, so that an attacker is difficult to obtain effective information from the ciphertext, and is difficult to crack under the condition of not knowing a secret key, thereby ensuring the safety of program code storage.

Disclosure of Invention

The invention provides a data encryption method of an MCU singlechip operating system, which aims to solve the existing problems.

The data encryption method of the MCU singlechip operating system adopts the following technical scheme:

an embodiment of the invention provides a data encryption method of an MCU singlechip operating system, which comprises the following steps:

acquiring a replaceable letter sequence of each letter in the letter sequence; acquiring a letter matrix; partitioning the letter matrix to obtain a plurality of partitioned letter matrices;

acquiring the frequency of each letter in the block letter matrix and the average frequency of the letters;

when the frequency of each letter is less than or equal to 5 times of the average frequency of the letters, randomly arranging all the letters in the letter sequence to obtain an alphanumeric mapping table; otherwise, taking the letters with the frequency more than 5 times of the average frequency of the letters as first candidate letters; acquiring a second candidate letter according to the replaceable letter sequence and the letter sequence of each first candidate letter, acquiring total run length and maximum run length according to the second candidate letter, combining all the first candidate letters in pairs to obtain a first letter combination, and acquiring the larger total frequency according to all the first letter combinations; when the total run length is larger than or equal to the larger total frequency, the character sequence is firstly subjected to large run length disorder operation and then subjected to small run length disorder operation to obtain a disorder sequence, and the disorder sequence is used as a character-number mapping table; when the total run-length is smaller than the larger total frequency, the character sequence is subjected to small run-length disorder operation firstly and then large run-length disorder operation to obtain a disorder sequence, and the disorder sequence is used as an alphanumeric mapping table;

and sequentially taking each letter in the block letter matrix as a letter to be encrypted, when the letter to be encrypted is the first letter in the block letter matrix, taking the first element in the replaceable letter sequence of the letter to be encrypted as a ciphertext of the letter to be encrypted, when the letter to be encrypted is not the first letter in the block letter matrix, acquiring the order of the ciphertext of the previous letter of the letter to be encrypted in the block letter matrix in an alphanumeric mapping table, taking the order as the first order, acquiring the element at the first order position of the replaceable letter sequence of the letter to be encrypted as the ciphertext of the letter to be encrypted, and storing the ciphertext.

Preferably, the large run out-of-order operation comprises:

dividing an input sequence into a plurality of maximum runs

The sub-sequence of (1), the first in the sub-sequence

An element asDivision points of which

Taking an element before a division point as a first element block, taking the division point and an element after the division point as a second element block, and splicing the first element block after the second element block to obtain a disordered subsequence; and splicing all the disordered subsequences according to the sequence of the subsequences to obtain the disordered sequence.

Preferably, the small run out-of-order operation includes:

and when the second element and the first element are adjacent in the alphabetical list, acquiring an element which is not adjacent to the first element in the alphabetical list, is positioned behind the first element in the input sequence and is closest to the first element as a third element, and exchanging positions of the third element and the second element.

Preferably, the alternative letter sequence of each letter in the acquired letter sequence includes:

the alternative letter sequence for each letter in the letter sequence includes all of the letters in the letter sequence and has a length of 26; all letters in the letter sequence have different elements in the same ordinal position in the alternative letter sequence.

Preferably, the blocking the alphabet matrix to obtain a plurality of blocked alphabet matrices includes:

converting the letter matrix into a digital matrix, and decomposing the digital matrix to obtain a sparse matrix; converting the sparse matrix into a sequence curve, converting the sequence curve into a frequency domain, and acquiring the reciprocal of the maximum frequency in the frequency domain as a period;

dividing the period by the number of columns of the letter matrix and rounding upwards to obtain the block length, dividing the letter matrix into a plurality of block letter matrices according to the block length, wherein the number of columns of the block letter matrices is equal to that of the letter matrix, and the number of rows of the block letter matrices is equal to that of the blocks.

Preferably, the obtaining the frequency of each letter and the average frequency of letters in the block letter matrix includes:

and counting the frequency of each letter and the number of the types of all the letters in the block letter matrix, and taking the reciprocal of the number of the types as the average frequency of the letters.

Preferably, the obtaining the second candidate letter according to the alternative letter sequence of each first candidate letter and the letter sequence comprises:

set a value to

The cumulative number of differences of (1), the first element in the alternative letter sequence of the first candidate letter is taken as the fourth element;

the fourth element is subjected to difference judgment, and the packet

Comprises the following steps: acquiring the next element of the fourth element in the replaceable letter sequence as a fifth element, and if the fifth element and the fourth element are not adjacent in the letter sequence, adding one to the difference cumulative number to take the fifth element as a new fourth element;

repeating the difference judgment operation on the new fourth element until the fifth element does not exist, stopping iteration, and dividing the accumulated number of the differences when the iteration is stopped by the value obtained by subtracting one from the length of the replaceable letter sequence to obtain the difference of the first candidate letter;

and taking the first candidate letter with the difference smaller than a first preset threshold value as a second candidate letter.

Preferably, the obtaining of the total run length and the maximum run length according to the second candidate letter comprises:

expressing each second candidate letter in the block letter matrix by using 1, expressing each element except 1 by using 0, calculating the ratio of the number of 1 to the number of 0 blocks to obtain the run-length of each second candidate letter, and dividing the run-length of each second candidate letter by the maximum value of the run-length of all second candidate letters to obtain the normalized run-length of each second subsequent letter; taking the sum of the normalized runability of all the second candidate letters as the total runability;

and acquiring the frequency of all runs of each second candidate letter in the block letter matrix, and taking the run corresponding to the maximum frequency in the runs of all the second candidate letters as the maximum run.

Preferably, the obtaining the total frequency greater according to all the first letter combinations includes:

acquiring the frequency number of each first letter combination in the block letter matrix as the first frequency number of each first letter combination; clustering all the first letter combinations into two types according to the first frequency of all the first letter combinations by using a clustering algorithm, and taking each first letter combination in the category with a large first frequency average value as a second letter combination;

dividing the first frequency count of each second letter combination by the maximum value in the first frequency counts of all the second letter combinations to obtain the frequency count of each second letter combination, wherein the frequency count is larger; and taking the sum of the frequency larger characters of all the second letter combinations as the total frequency larger character.

The technical scheme of the invention has the beneficial effects that:

1. because the letter types and the number of the letters in different block letter matrixes are different from each other, the letter-number mapping tables of the different block letter matrixes are adaptively set according to the frequency information of each letter in the block letter matrixes, so that the difference between the different block letter matrixes is increased, even if the letters of the two block letter matrixes are the same, the letter-number mapping tables are different, and the corresponding replaced letters are different, on one hand, the disorder among ciphertexts can be increased, and the cracking difficulty is increased; on the other hand, the calculation of the letter frequency is a very simple method, namely, the encryption method is simple, the calculation amount is small, and a good encryption effect can be achieved;

2. the next letter is encrypted by combining the ciphertext of the previous letter, so that the ciphertexts of different letters have strong correlation, if one letter is changed, the ciphertexts of all the following letters are changed, the disorder of the ciphertexts is increased, the difference between the ciphertexts after encryption and the original plaintext is large, an attacker is further difficult to obtain effective information from the ciphertexts, and the ciphertexts are difficult to crack under the condition of not knowing a secret key, so that the safety of program code storage is improved;

3. the data volume of the letter matrix is large, on one hand, the whole encryption easily causes an attacker to intercept and obtain a ciphertext and then tamper the ciphertext, which directly causes a large amount of data errors, on the other hand, the method can decrypt and obtain all the plaintext after the attacker guesses a secret key, and blocks the letter matrix, and encrypts each block letter matrix by using different alphanumeric mapping tables, on the one hand, the attacker cannot cause a large amount of data errors even if tampering the ciphertext of one block letter matrix, but only causes the data errors of the corresponding block letter matrix, and on the other hand, the attacker only causes the content of the block letter matrix corresponding to the part of the secret key to be leaked, and cannot cause all the plaintext to be leaked even if guessing the part of the secret key. The robustness of the encryption method is enhanced through the blocking, so that the program code is stored more safely.

Drawings

In order to more clearly illustrate the embodiments of the present invention 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 some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a flow chart of the steps of a data encryption method of an MCU singlechip operating system according to the invention;

FIG. 2 is a schematic diagram of an alphabet matrix-to-digital matrix of the data encryption method of the MCU singlechip operating system of the invention;

FIG. 3 is a schematic diagram of an encryption process of the data encryption method of the MCU singlechip operating system according to the invention.

Detailed Description

In order to further explain the technical means and effects of the present invention adopted to achieve the predetermined purpose, the following detailed description, with reference to the accompanying drawings and preferred embodiments, describes a data encryption method of the MCU one-chip microcomputer operating system according to the present invention, and its specific implementation, structure, features and effects thereof. In the following description, different "one embodiment" or "another embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

The following describes a specific scheme of the data encryption method of the MCU singlechip operating system provided by the invention in detail with reference to the accompanying drawings.

Referring to fig. 1, a flowchart of steps of a data encryption method for an MCU monolithic processor operating system according to an embodiment of the present invention is shown, where the method includes the following steps:

and S001, acquiring letters in the program, and converting the letters into a letter matrix.

It should be noted that, the number of english letters is 26, and the probability of repeated words existing in the program is high, so that the partial letter arrangement has a certain rule. The data can be blocked, and different keys are set for the data of different blocks to prevent the encrypted ciphertext from reflecting the arrangement rule of letters in the plaintext. In order to block data, the data needs to be converted into a matrix format first.

In this embodiment, the number of letters in the program is first obtained by statistics, and all the letters in the program are converted into a matrix with similar rows and columns, which is called a letter matrix, according to the number of letters. For example: a 100 letter program translates into a 10 x 10 letter matrix. In the conversion process, if the number of letters in a certain row or a certain column is less than the number of columns or rows, 0 complementing operation is performed on the row or the column. It should be noted that, in the present embodiment, only the letters in the program are converted into the matrix format, and other data, such as symbols and numbers in the program, are not changed.

And S002, partitioning the letter matrix to obtain a partitioned letter matrix.

It should be noted that, when the alphabet matrix is partitioned, the alphabet matrix may be partitioned according to the periodicity of the alphabet data in the alphabet matrix, and each block is encrypted by using different keys, so that the periodicity of the plaintext is not reflected in the ciphertext. RPCA (robust principal component analysis) is a method for decomposing an original matrix into a low-rank matrix and a sparse matrix, wherein different rows of the low-rank matrix are linearly related and can represent the relation or similar characteristics between the different rows, the sparse matrix is equivalent to noise data, and if the noise data of certain rows are similar, the relevance of the corresponding rows on the original matrix is large, so that the original matrix can be partitioned by calculating the data rule in the sparse matrix. Since RPCA is directed to a number matrix, the letter matrix is first converted to a number matrix.

In this embodiment, each letter in the letter matrix is used in

The order in English alphabet is used for representation, and a number matrix is obtained. As shown in fig. 2, letters

Is composed of

The first element of the English alphabet, and thus the letters of the alphabet matrix

The value of the element of the corresponding position in the number matrix is

Letter of Chinese character

Is composed of

A second element of the English alphabet, thus a letter of the alphabet matrix

Elements of corresponding positions in the number matrixHas a value of

The letters in the letter matrix

The value of the element of the corresponding position in the number matrix is

。

It should be noted that the periodicity of the alphabet matrix is not calculated directly, but calculated after the digit matrix is decomposed by the RPCA, because the result obtained by calculating the periodicity directly by the alphabet matrix can only represent the overall similarity between different data, and cannot represent the trend similarity, for example

And

the data change trends of (1) are different, but the cosine similarity is large, and the cosine similarity can only represent the overall similarity between the data and cannot represent the trend similarity. And the low-rank matrix obtained by RPCA decomposition represents the relation among data, the same characteristics among all data of the original matrix are represented, and the trend similarity among different data of the original matrix can be obtained by analyzing the sparse matrix, wherein the sparse matrix represents the unique characteristics of each data of the original matrix. Therefore, in the embodiment, the original matrix is partitioned according to the data rule of the sparse matrix after RPCA decomposition.

In this embodiment, after the letter matrix is converted into the number matrix, a sparse matrix is obtained through RPCA decomposition, a mode that adjacent rows of the sparse matrix are connected (the beginning of the second row is connected to the end of the first row, and the beginning of the third row is connected to the end of the second row) is converted into a sequence curve, the sequence curve is converted into a frequency domain by fourier transform, and the maximum frequency in the frequency domain is obtained. The maximum frequency reflects the most frequent change of the data, and the period corresponding to the maximum frequency is taken as the period of the letter matrix to reflect the change rule of the data in the letter matrix. The period corresponding to the maximum frequency is the inverse of the maximum frequency.

The size of the period reflects the number of data in the period, the period is divided by the number of columns of the letter matrix and rounded up, the obtained result is taken as the block length, and the block length reflects the closest number of rows of the period size in the letter matrix. And dividing the letter matrix into a plurality of block letter matrixes according to the block length, wherein the column number of each block letter matrix is equal to that of the letter matrix, and the row number of each block letter matrix is equal to the block length. E.g. number of rows of letter matrix

Block length of

Time, letter matrix

To

Action first block letter matrix, letter matrix

To

Act second block letter matrix, letter matrix

To

The behavior is the third block letter matrix.

Therefore, the blocking of the letter matrix is realized, and the blocking letter matrix is obtained. The purpose of blocking is that because the similarity between different blocking letter matrixes in the letter matrix is larger, in order to not embody the information in the ciphertext and increase the cracking difficulty, the different blocking letter matrixes are encrypted by using different keys by blocking the letter matrix, so that the ciphertext is more complex and is difficult to crack. Meanwhile, due to the fact that the data volume of the letter matrix is large, on one hand, an attacker is easy to capture the ciphertext and then tamper the ciphertext after intercepting the ciphertext to directly cause a large number of data errors, on the other hand, the attacker can decrypt the ciphertext to obtain all plaintext after guessing the key to obtain the other method, the letter matrix is partitioned, and each partitioned letter matrix is encrypted by using different keys respectively. The robustness of the encryption method is enhanced by blocking.

And S003, acquiring a replaceable letter sequence of each letter in each block letter matrix.

The English letters are

If the letter sequence table is used as the letter sequence, the encryption end and the decryption end agree in advance with the replaceable letter sequence of each letter in the letter sequence, and the length of the replaceable letter sequence of each letter is

And comprise all

The sequence of the English letters, and the elements of the same sequence position in the replaceable letter sequences of all the letters are different. And constructing all letters and the corresponding alternative letter sequences of the letters into an encryption dictionary.

For example: letters

The alternative letter sequence of

Letter of Chinese character

The alternative letter sequence of

Letter of Chinese character

The alternative letter sequence of

And the like.

It should be noted that there are multiple encryption dictionaries meeting the condition, and both the encryption side and the decryption side can agree with multiple encryption dictionaries in advance, and different block letter matrices are encrypted by using different encryption dictionaries. Meanwhile, the encryption end and the decryption end can replace the encryption dictionary at intervals so as to improve the confidentiality effect.

And S004, acquiring the total run length and the larger total frequency of each block letter matrix.

It should be noted that, in the encryption method in this embodiment, a sequence of a ciphertext of a letter previous to a current letter to be encrypted in the block letter matrix in the alphanumeric mapping table is taken as a first time, and an element at a first time position in the replaceable letter sequence of the current letter to be encrypted is obtained as the ciphertext of the current letter to be encrypted. In the encryption process, an alphanumeric mapping table is applied, which is a mapping relation table indicating the number corresponding to each letter. Alphanumeric maps, if implemented as specified, are susceptible to leakage during long-term encryption. To avoid this problem, the alphanumeric mapping table may be adaptively obtained according to the alphabet appearance rule in the block alphabet matrix, so as to improve the encryption effect. If the alphanumeric mapping table is randomly set, the encryption effect cannot be guaranteed to be always good, and the following two extreme cases may occur:

1. in the ciphertext corresponding to the same continuous letter, the context of the letter elements in the corresponding replaceable letter sequence in the letter is easy to expose.

In the combination of the replaceable letter sequences of all the letters, when the element sequence in the replaceable letter sequence of some letters is close to the element sequence of 26 English letters to a greater extent, the continuous ciphertext of the same letter easily exposes the context of the element letters in the replaceable letter sequence of the letter (the rule is easily obtained through long-time cracking). For example when

Is a sequence of replaceable letters of

，

The alternative letter sequence of

Meanwhile, when the alphanumeric mapping table of each letter is the same as the English alphabet sequence table, the plaintext is assumed to be

Then the encrypted ciphertext is

. When the more letters appear in plain text continuously, an attacker can find the same ciphertext in the process of cracking different block letter matrixes

Occur many times, increasing the risk of being compromised.

This problem may arise when the order of elements in the alternative alphabetic sequence of certain letters is similar to the alphabetic order in an english alphabetic ordering list. To avoid this problem, the alphanumeric mapping table needs to be adjusted so that the order of the elements in the alphanumeric mapping table is different from the order of the letters in the english alphabetical order table, and different alphanumeric mapping tables are applied to different blocks, thereby increasing security.

2. The greater the probability of occurrence of a combination of two letters, the easier it is for an attacker to obtain the mapping relationship in the alphanumeric mapping table.

For example letters

And

alternative letter sequences and cases of

The same as Chinese, while when the alphanumeric mapping table of each letter is the same as the English alphabetical sequence table, the plaintext

Is a ciphertext of

Converting the cipher text into its number in the English alphabet order table as

. It can be seen that the first appearance in the plain text

The number of the corresponding ciphertext is

Second occurrence in the plaintext

The number of the corresponding ciphertext is

(ii) a First appearance in the plain text

The number of the corresponding ciphertext is

Second occurrence in the plaintext

The number of the corresponding ciphertext is

. Clear text from the above

When they appear continuously, the intervals of the numbers of the corresponding cipher texts are all

And clear text

. This rule is easy for an attacker to crack the plaintext.

To avoid this problem, the alphanumeric mapping table needs to be adjusted so that adjacent letters in the alternative letter sequence that combine letters with a high frequency of occurrence are further apart in the alphanumeric mapping table.

The two extreme cases are problems that the order of elements in the replaceable alphabetical sequence of some letters is similar to the order of letters in the English alphabetical sequence table, and the alphanumeric mapping table is similar to the English alphabetical sequence table. Therefore, the difference between the replaceable letter sequence of the letter with high frequency in the block letter matrix and the English letter sequence table is calculated, when the difference is large, the two extreme conditions cannot occur, and the alphanumeric mapping table can be randomly set. Conversely, when the difference is small, the above extreme cases may occur, and at this time, the probabilities of the two extreme cases need to be analyzed according to the block alphabet matrix, so as to set the alphanumeric mapping table.

In this embodiment, the frequency of occurrence of each letter in the block letter matrix and the number of kinds of letters occurring in the block letter matrix are first counted. The reciprocal of the number of the kind is taken as the average frequency of the letters, for example, 18 letters are in total in a block letter matrix, then the average frequency of the letters is

. Letters with a frequency greater than 5 times the average frequency of the letters can be considered to be more frequent and are referred to as first candidate letters.

The two extreme cases are all premised on that the run length of some letters is large or the occurrence frequency of some letter combinations is large, if the first candidate letter does not exist, the run length of each letter is not large or the occurrence frequency of some letter combinations is not large, at the moment, the two extreme cases cannot occur, and an attacker cannot analyze the replaceable letters corresponding to the same letter in the plaintext through the ciphertext. Therefore, when the first candidate letter does not exist, an alphanumeric mapping table is randomly set, namely all letters in the letter sequence are randomly arranged to obtain the alphanumeric mapping table, wherein the letter sequence is an English letter sequence table.

When first candidate letters exist, calculating the difference between the replaceable letter sequence of each first candidate letter and the English letter sequence table to obtain the difference of each first candidate letter, wherein the specific method comprises the following steps:

set a value to

The cumulative number of differences of (2) takes the first element in the alternative letter sequence of the first candidate letter as the fourth element. Obtaining the fourth element in the alternativeAnd replacing the next element in the letter sequence as a fifth element, and if the fifth element and the fourth element are not adjacent in the English letter sequence table, adding one to the difference cumulative number, and using the fifth element as a new fourth element. Repeating the above operations, carrying out difference judgment operation on the new fourth element until the fifth element does not exist, stopping iteration, and dividing the accumulated number of differences when iteration is stopped by the value obtained by subtracting one from the length of the replaceable letter sequence to obtain the difference of the first candidate letter.

Such as letters

Is a sequence of replaceable letters of

The initial cumulative number of differences is

，

As a fourth element, a group of elements,

is a fifth element and is a compound of the first element,

and

adjacent in the English letter sequence table, at this moment, the difference accumulated number is unchanged;

as a fourth element, a group of elements,

is a fifth element which is a function of,

and

the difference cumulative number is increased by one when the English letters are not adjacent in the sequence table; in the same way, the method for preparing the composite material,

and

adjacent in the English alphabetical order list, the difference accumulation number is not changed at the moment;

and

the difference cumulative number is increased by one when the English letters are not adjacent in the English letter sequence table;

and

the difference accumulation numbers are increased by one when the English alphabetical ordering list is not adjacent. The final cumulative difference number is

. Letters

Alternative letter sequences of

Has a length of

Then letter

Has a difference of

。

It should be noted that the difference between each element in the alternative letter sequence and the letter in the same position in the English alphabet sequence table is not directly calculated, for example, because of the alternative letter sequence

The difference from the english alphabet list is small, but the difference between each element in the replaceable alphabet sequence and the letter in the same position in the english alphabet list makes the obtained numerical value larger, which results in larger error.

In this embodiment, the difference is smaller than a first preset threshold

As a second candidate letter. In the present embodiment

In other embodiments, the implementer may set the value of the first preset threshold as desired.

For each second candidate letter, all letters except the second candidate letter in the block letter matrix are represented by 0, the second candidate letter is represented by 1, when 0 appears continuously, 0 appearing continuously is regarded as one block, then the ratio of the number of 1 to the number of blocks of 0 is calculated, and the ratio is taken as the runability of the second candidate letter. For example: for block alphabet matrices

In other words, when calculating

When the run-length is required, the block letter matrix is firstly converted into

At this time

Is in an amount of

，

Number of blocks of

Then, then

Has a run-length of

. For block alphabet matrices

In other words, when calculating

At this time

Is in an amount of

，

Number of blocks of

Then, then

Has a run-length of

. It should be noted that the greater the run length, the more likely the above extreme case 1 occurs, and in this case, the more necessary the alphanumeric mapping table needs to be set for the run length to avoid the extreme case 1.

And dividing each run-length in the block letter matrix by the maximum value of the run-lengths of all the second candidate letters to obtain the normalized run-length of each second subsequent letter. The sum of the normalized runability of all second candidate letters is taken as the total runability. The total runability reflects the possibility of the occurrence of extreme case 1, and when the total runability is larger, the more necessary it is to set the alphanumeric mapping table for the runlength to avoid extreme case 1.

For the extreme case 2, the combination property between the first candidate letters needs to be calculated, all the first candidate letters are combined pairwise to obtain all possible combinations, and each obtained combination is used as a first letter combination. And counting the frequency number of each first letter combination in the block letter matrix as the first frequency number of each first letter combination. And clustering all the first letter combinations into two types according to the first frequency numbers of all the first letter combinations by utilizing a clustering algorithm, and taking each first letter combination in the category with the large first frequency number mean value as a second letter combination. The second letter combination is a letter combination with a high frequency of occurrence in the block letter matrix. Dividing the first frequency count of each second letter combination by the maximum value in the first frequency counts of all the second letter combinations to obtain the larger frequency count of each second letter combination, wherein the larger the frequency count is, the more likely the extreme case 2 occurs, and at this time, the more necessary the alphanumeric mapping table needs to be set for the letter combinations to avoid the extreme case 2. And taking the sum of the frequency larger characters of all the second letter combinations as the total frequency larger character. The greater the total frequency reflects the possibility of the occurrence of the extreme case 2, and when the greater the total frequency, the more necessary the alphanumeric mapping table needs to be set for the combination of letters to avoid the extreme case 2.

When the second candidate letter does not exist, the total run-length does not exist, and at this time, the total run-length is recorded as 0, and when the second letter combination does not exist, the total frequency is not large, and at this time, the total frequency is large and is recorded as 0.

Therefore, the total run-length and the total frequency are larger. The total run length and the large total frequency reflect the possibility of two extreme conditions, and the two extreme conditions can be avoided as much as possible when an alphanumeric mapping table is set subsequently according to the total run length and the large total frequency, so that the encryption result is more complex, and the statistical analysis attack is resisted.

And S005, acquiring an alphanumeric mapping table in a self-adaptive manner according to the total run length and the total frequency greater.

When the total run length is 0 and the total frequency is greater than 0, the second candidate letter does not exist and the second letter combination does not exist, which indicates that the run length of each letter is not great and the occurrence frequency of the letter combination is not large, and at this time, the two extreme situations described in step S004 do not occur, and an attacker cannot analyze the replaceable letter corresponding to the same letter in the plaintext through the ciphertext. Therefore, when the total run length is 0 and the total frequency is 0, an alphanumeric mapping table is randomly set, that is, all letters in the letter sequence are randomly arranged to obtain the alphanumeric mapping table, wherein the letter sequence is an English letter sequence table.

It should be noted that when the total run length is not 0 or the total frequency is not 0 significantly, the two extreme cases described in step S004 may occur, and the alphanumeric mapping table needs to be set to a sequence with a large difference from the english alphabet table. When the total run length is larger, extreme case 1 can be avoided by setting an alphanumeric mapping table to increase the difference of consecutive letters in the block alphabet matrix (where the difference refers to the meaning of the difference in step S004, and the difference here is no longer just considering 1 neighborhood letter, and needs to consider a larger range of neighborhood letters). When the total frequency is larger, the extreme case 2 can be avoided by setting the alphanumeric mapping table to increase the difference between the letters in the block alphabet matrix and the letters before and after the letter in the block alphabet matrix in the alphanumeric mapping table (where the difference refers to the meaning of the difference in step S004, and only 1 neighborhood letter is considered here). For example, the run of the second candidate alphabet is 3, in order to avoid the extreme case 1, the difference of the 3 neighborhood alphabets needs to be considered, and in order to avoid the extreme case 2, because of the alphabet combination, only the 1 neighborhood alphabet (the difference is calculated before, and the 1 neighborhood alphabet is considered) needs to be considered.

In this embodiment, first, the frequency counts of all runs of each second candidate letter in the block letter matrix are obtained, and the run corresponding to the largest frequency count among the runs of all the second candidate letters is taken as the largest run and is marked as the largest run

。

Denote the total run-length as

The greater frequency of the total frequency is recorded as

. The letter sequence, i.e. English letter sequence table, is used as the initial alphanumeric mapping table.

When in use

And then, the influence of the large run is larger, and the extreme condition 1 is more likely to occur, at this time, the large run out-of-order operation needs to be carried out on the letter sequence to avoid the extreme condition 1, the small run out-of-order operation is further carried out to avoid the extreme condition 2, and the sequence obtained after the large run out-of-order operation and the small run out-of-order operation is used as an alphanumeric mapping table.

When the temperature is higher than the set temperature

In time, it is stated that the influence of small runs is large, and extreme case 2 is more likely to occur, and at this time, it is necessary to first perform small run shuffling on the letter sequenceAnd (3) avoiding an extreme case 2 by the sequence operation, further avoiding an extreme case 1 by the large run out-of-order operation, and taking a sequence obtained after the small run out-of-order operation and the large run out-of-order operation as an alphanumeric mapping table.

The large run out-of-order operation specifically comprises:

recording the sequence needing large run out-of-order operation as input sequence, dividing the input sequence into multiple run lengths with maximum length

The sub-sequence of (1), the first in the sub-sequence

The elements are used as dividing points, wherein

And in order to get the rounded character upwards, taking the elements before the division point as a first element block, taking the division point and the elements after the division point as a second element block, and splicing the first element block after the second element block to obtain the disordered subsequence. And splicing all the disordered subsequences according to the sequence of the subsequences to obtain the disordered sequence. For example, the manual input sequence is

Maximum run length

First, the input sequence is

Is divided into a plurality of lengths of

Of (a) a subsequence

、

. Will be the second in each subsequence

An element as a division point, e.g.

In

For the division point, the element before the division point is used as the first element block

Taking the division point and the elements after the division point as a second element block

Splicing the first element block after the second element block to obtain an out-of-order subsequence

. The same reason is that

Out of order subsequence of

. All out-of-order subsequences

、

Splicing according to the sequence of the subsequences to obtain an out-of-order sequence

. It should be noted that the reason why the out-of-order operation of large runs does not use the reverse order but uses the division method of division points is that in the reverse order relationship, for example

In the reverse order of

The original adjacent relationship is still maintained, so the present embodiment selects the middle position as the start data (i.e. the segmentation point) to perform blocking on the subsequence, and joins different blocks out of order as the result of the large run out of order operation.

The small run out-of-order operation specifically comprises:

and recording a sequence needing small run out-of-order operation as an input sequence, sequentially taking each element in the input sequence as a first element, taking the next element of the first element as a second element, when the second element is adjacent to the first element in the English alphabetic ordering list, acquiring an element which is not adjacent to the first element in the English alphabetic ordering list, is positioned behind the first element in the input sequence and is closest to the first element as a third element, and exchanging positions of the third element and the second element. For example, the input sequence is

First, the

As the first element, it is preferable that,

as the second element, it is preferable that,

and

adjacent to the first element in the English alphabet list

Non-adjacent and located at the first element in the input sequence

Then and from the first element

The most recent elements

As a third element, a third element

With a second element

Exchange positions to obtain

. Will be provided with

As the first element, it is preferable that,

as a second element, a first element

With a second element

If not adjacent in the English letter sequence table, do not operate, the same way

And

are not adjacent in the English alphabetical order list,

and

are not adjacent in the English alphabetical order list,

and

if the English letters are not adjacent in the English letter sequence list, no operation is performed. The final result is

. A schematic of encryption is shown in fig. 3.

Thus, an alphanumeric mapping table is obtained. Because the number of the letter types in different block letter matrixes and the frequency of each letter are different, the alphanumeric mapping tables of the different block letter matrixes are adaptively set according to the frequency and the run length information of the letters, so that each block letter matrix is encrypted according to the alphanumeric mapping tables in the following process, the ciphertext differences of the different block letter matrixes are increased, the letters of the two block letter matrixes are the same, the obtained alphanumeric mapping tables are different, the ciphertexts obtained in the following encryption process are different, on one hand, the disorder among the ciphertexts can be increased, and the cracking difficulty is increased; on the other hand, the calculation of the letter frequency is a very simple method, namely, the encryption method is simple, the calculation amount is small, and a good encryption effect can be achieved.

And S006, encrypting each block letter matrix according to the letter number mapping table and the replaceable letter sequence to obtain a ciphertext.

And when the letter to be encrypted is not the first letter in the block letter matrix, acquiring the order of the ciphertext of the previous letter of the letter to be encrypted in the block letter matrix in an alphanumeric mapping table, and acquiring the element at the first order position of the replaceable letter sequence of the letter to be encrypted as the ciphertext of the letter to be encrypted.

E.g. a block alphabet matrix of

First, the

As a letter to be encrypted, obtaining

The first element in the replaceable letter sequence is used as the letter to be encrypted

Is expressed as

Obtaining, by means of an alphanumeric mapping table

The order in the middle alphanumeric mapping table is taken as the first order, denoted as

(ii) a Will be provided with

As a letter to be encrypted, obtaining

First in alternative letter sequences

One element as a letter to be encrypted

Will be described as

Then byAlphanumeric mapping table, obtaining

The order in the medium alphanumeric mapping table is taken as the first order, and is recorded as

(ii) a Will be provided with

As a letter to be encrypted, obtaining

First in alternative letter sequences

One element as a letter to be encrypted

Is expressed as

Then through the alphanumeric mapping table, obtain

(ii) a Will be provided with

As a letter to be encrypted, obtaining

First in alternative letter sequences

One element as a letter to be encrypted

Is expressed as

. Thus realizing the block letter matrix

Is encrypted as

。

At this point, the encryption of the block alphabet matrix is completed. In the embodiment, the next letter is encrypted by combining the ciphertext of the previous letter, so that the ciphertexts of different letters have strong correlation, if one letter is changed, the ciphertexts of all the letters are changed, the disorder of the ciphertexts is increased, the difference between the ciphertexts after encryption and the original plaintext is large, an attacker is further difficult to obtain effective information from the ciphertexts, and the cipher is difficult to crack under the condition of not knowing a secret key, so that the data security is improved.

And taking the total run length and the total frequency of each block letter matrix as a first supplementary key, and taking the maximum run length of each block letter matrix as a second supplementary key. And encrypting the first supplementary key and the second supplementary key by using an asymmetric encryption algorithm, and recording an encryption result as a supplementary ciphertext. It should be noted that, in this embodiment, only the first supplemental key and the second supplemental key are encrypted by using the asymmetric encryption algorithm, and the block alphabet matrix is not directly encrypted by using the asymmetric encryption algorithm, because the asymmetric encryption algorithm has strong security but a slow encryption and decryption speed, and is not suitable for encrypting data with a large data amount, but is only suitable for encrypting data with a small data amount. The data volume of the block letter matrix is large, and the encryption efficiency is low by adopting an asymmetric encryption algorithm, so that the encryption method in the embodiment needs to be adopted for encryption.

And storing the ciphertext of all the block letter matrixes and the supplementary ciphertext in a memory of the MCU singlechip operating system.

And S007, decrypting the ciphertext.

When the ciphertext is decrypted, the ciphertext and the supplementary ciphertext need to be obtained at the same time, firstly, the supplementary ciphertext is decrypted by using an asymmetric encryption algorithm to obtain a first supplementary key and a second supplementary key, the first supplementary key is the total run length and the total frequency of each block letter matrix, and the second supplementary key is the maximum run length of each block letter matrix.

The alphanumeric mapping table for each block alphabet matrix is obtained using the method in step S005. And decrypting the ciphertext according to the ciphertext of each block letter matrix and the alphanumeric mapping table:

sequentially taking each letter in the ciphertext as a first ciphertext, when the first ciphertext is the first letter in the ciphertext, acquiring the first element of the replaceable letter sequence of all the letters as a candidate decryption letter, and acquiring a letter corresponding to a subsequent decryption letter which is the same as the first ciphertext as a plaintext of the first ciphertext; when the first ciphertext is not the first letter in the ciphertext, taking the order of the previous letter in the ciphertext of the first ciphertext in the alphanumeric mapping table as a first order, obtaining the first order elements of the replaceable letter sequences of all letters as candidate decryption letters, and obtaining the letter corresponding to the candidate decryption letter which is the same as the first ciphertext as the plaintext of the first ciphertext.

Similarly, the plaintext of each block letter matrix can be obtained, and further the program code can be obtained.

Through the steps, the encryption and decryption of the program in the MCU singlechip operating system are completed.

According to the embodiment of the invention, the alphanumeric mapping tables of different block alphabetic matrices are set in a self-adaptive manner according to the frequency information of each letter of the block alphabetic matrices, so that the difference between the different block alphabetic matrices is increased, even if the letters of the two block alphabetic matrices are the same, the alphanumeric mapping tables are different, and the corresponding replaced letters are different, thereby on one hand, the disorder between ciphertexts can be increased, and the cracking difficulty is increased; on the other hand, the calculation of the letter frequency is a very simple method, namely, the encryption method is simple, the calculated amount is small, and a good encryption effect can be achieved; the next letter is encrypted by combining the ciphertext of the previous letter, so that the ciphertexts of different letters have strong correlation, if one letter is changed, the ciphertexts of all the following letters are changed, the disorder of the ciphertexts is increased, the difference between the ciphertexts after encryption and the original plaintext is large, an attacker is further difficult to obtain effective information from the ciphertexts, and the ciphertexts are difficult to crack under the condition of not knowing a secret key, so that the safety of program code storage is improved; the data volume of the letter matrix is large, on one hand, the whole encryption easily causes an attacker to intercept and obtain a ciphertext and then tamper the ciphertext, which directly causes a large amount of data errors, on the other hand, the method can decrypt and obtain all the plaintext after the attacker guesses a secret key, and blocks the letter matrix, and encrypts each block letter matrix by using different alphanumeric mapping tables, on the one hand, the attacker cannot cause a large amount of data errors even if tampering the ciphertext of one block letter matrix, but only causes the data errors of the corresponding block letter matrix, and on the other hand, the attacker only causes the content of the block letter matrix corresponding to the part of the secret key to be leaked, and cannot cause all the plaintext to be leaked even if guessing the part of the secret key. The robustness of the encryption method is enhanced through the blocking, so that the program code storage is safer.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A data encryption method of an MCU singlechip operating system is characterized by comprising the following steps:

2. The data encryption method of the MCU singlechip operating system according to claim 1, wherein the large run out-of-order operation comprises:

dividing an input sequence into a plurality of maximum runs

The sub-sequence of (1), the first in the sub-sequence

Taking the elements as dividing points, wherein the elements are rounded up, taking the elements before the dividing points as first element blocks, taking the dividing points and the elements after the dividing points as second element blocks, and splicing the first element blocks after the second element blocks to obtain disordered subsequences; and splicing all the disordered subsequences according to the sequence of the subsequences to obtain the disordered sequences.

3. The data encryption method of the MCU singlechip operating system according to claim 1, wherein the small run out-of-order operation comprises:

and when the second element is adjacent to the first element in the alphabetical list, acquiring an element which is not adjacent to the first element in the alphabetical list, is positioned behind the first element in the input sequence and is closest to the first element as a third element, and exchanging positions of the third element and the second element.

4. The data encryption method of the MCU singlechip operating system according to claim 1, wherein the acquiring the replaceable letter sequence of each letter in the letter sequence comprises:

5. The data encryption method of the MCU singlechip operating system according to claim 1, wherein the blocking the alphabet matrix to obtain a plurality of blocked alphabet matrices comprises:

6. The data encryption method for the MCU singlechip operating system according to claim 1, wherein the acquiring the frequency of each letter and the letter average frequency in the block letter matrix comprises:

7. The data encryption method for the MCU singlechip operating system according to claim 1, wherein the obtaining a second candidate letter according to the letter sequence and the replaceable letter sequence of each first candidate letter comprises:

set a value to

and performing difference judgment on the fourth element, including: acquiring the next element of the fourth element in the replaceable letter sequence as a fifth element, and if the fifth element and the fourth element are not adjacent in the letter sequence, adding one to the difference cumulative number to take the fifth element as a new fourth element;

repeating the difference judgment operation on the new fourth element until the fifth element does not exist, stopping iteration, and dividing the accumulated number of differences when the iteration is stopped by the value obtained by subtracting one from the length of the replaceable letter sequence to obtain the difference of the first candidate letter;

8. The data encryption method of the MCU singlechip operating system according to claim 1, wherein the obtaining the total run length and the maximum run length according to the second candidate letter comprises:

9. The data encryption method for the MCU singlechip operating system according to claim 1, wherein the obtaining the larger total frequency according to all the first letter combinations comprises:

acquiring the frequency count of each first letter combination in the block letter matrix as the first frequency count of each first letter combination; clustering all the first letter combinations into two types according to the first frequency of all the first letter combinations by using a clustering algorithm, and taking each first letter combination in the category with a large first frequency average value as a second letter combination;