CN103117850A - Cryptosystem based on random sequence database - Google Patents

Abstract

The invention provides a cryptographic system based on a random sequence database. The cryptographic system transforms the binary bit stream into a random sequence bit stream through an 8-bit binary number composed of 256 pieces of data and its corresponding random sequence database D. The conversion of the random sequence database D to the binary bit stream is realized by character string searching. The random sequence database D can be dynamically updated and synchronized by encrypting or decrypting one byte at a time. This password system is a real "one-time pad" perfect password system, which is completely undecipherable.

Description

A Cryptosystem Based on Random Sequence Database

technical field

The invention belongs to the field of information security, in particular to a password system based on a random sequence database.

Background technique

Cryptography system is the core and key technology of information security. Although there are many kinds of cryptographic systems in practical application at present, their cryptosystems can be divided into two categories: symmetric cryptosystems and asymmetric cryptosystems. In 1949, Shannon published an important paper on "Communication theory of secrecy system", proving that only the "one-time pad" cryptographic system is theoretically undecipherable and absolutely secure. However, due to the extremely difficult problems of key generation, distribution and management in the "one-time pad" cryptographic system, its application is limited. In order to achieve the security similar to "one-time pad", cryptosystems imitating "one-time pad" such as block cipher and stream cipher are applied. Currently, stream ciphers are the mainstream ciphers in the field of information security around the world. There are many design methods for stream ciphers, such as shift register sequence, nonlinear combination sequence, nonlinear filter sequence, clock control sequence and chaotic sequence.

Stream cipher refers to the use of a small number of keys to generate a large number of pseudo-random bit streams through specific complex cryptographic algorithms, which are used to encrypt plaintext bit streams. Decryption refers to using the same key and cryptographic algorithm and the same pseudo-random bit stream as encryption to restore the plaintext bit stream. Therefore, the key of the stream cipher is the algorithm for generating the key sequence, and the security of the cryptographic system mainly depends on the key sequence, but since the key sequence is mostly generated by a certain seed key k through a specific deterministic algorithm Therefore, the stream cipher is a cryptographic system based on mathematical calculations, which can be deciphered by a computer in theory. Therefore, in essence, a stream cipher is not a "one-time pad" cryptographic system.

The present invention proposes a cryptographic system based on a random sequence database, which is similar to a stream cipher, which encrypts one byte at a time, but the stream cipher uses a pseudo-random sequence as the key sequence, while this cryptosystem uses a random sequence The database transforms the plaintext stream into a random sequence. The present invention provides a "one-time-one-pass" perfect password system, which can not be deciphered at all, and can also automatically detect the integrity of the ciphertext information to ensure that the ciphertext information is not tampered with or counterfeited, and can be widely used in various fields of information security .

Contents of the invention

A kind of password system based on random sequence database that the present invention establishes, take following steps and method:

(1) First, build an 8-bit binary database D.

The structure of the database is shown in Figure 1, A is an 8-bit binary number, and B is a random sequence corresponding to each binary number (such as a random sequence composed of 0 and 1). Use A(i) to represent the 8-bit binary number of 0-255, and B(i) to represent the random sequence corresponding to A(i). The setting of the sequence length of B(i) is based on the sufficient guarantee of the uniqueness of the random sequence ki and the operation speed of the sequence search. The database D has a total of 256 pieces of data. Since 2 ¹⁶ =2 ⁸ *2 ⁸ =256*2 ⁸ =256*256, corresponding to 256 pieces of binary data, each 8-bit binary data can theoretically find 256 different 16-bit binary random sequences corresponding to it correspond. It is sufficient to set the length of each random sequence B(i) between 30-100 characters.

(2) Encryption method:

First convert the plaintext M into binary, and then automatically divide each byte, that is, an 8-bit binary number, into several units, such as m ₁ , m ₂ , m ₃ ,..., m _n . Then, search in the database D in turn, find the corresponding random sequence B(i) according to the retrieved 8-bit binary number A(i), and then randomly intercept a section of 16-character sequence in B(i) sequence ki. When all the bytes of the plaintext M are transformed above, k ₁ , k ₂ , k ₃ , ..., k _n are sequentially obtained, which constitutes the ciphertext. The random sequence ki can also undergo encryption transformation Ci=E(k _i ) (i=1, 2, 3, ..., n), and finally the ciphertext C = c ₁ c ₂ c ₃ ... c _n can be obtained.

Among them, k ₁ , k ₂ , k ₃ ,..., k _n need to meet the uniqueness condition, that is, in the database D, these random sequences ki are unique, if the intercepted ki cannot meet the uniqueness condition, it must be re- Select until the uniqueness condition is met. To check the uniqueness of ki, you can use a string search algorithm to search in database D. If ki has only one search result, it means that ki is unique in database D, otherwise it is not unique.

(3) Key dynamic update method:

During the encryption process, the key can be automatically updated after encrypting one byte (8-bit binary number m _i ) of plaintext each time. The update method is: after the random sequence corresponding to _mi is intercepted by a subsequence ki, that is It is automatically deleted from the original random sequence, and inserted into the jth position in the random sequence after ki is deleted after a certain transformation (such as 0 and 1 exchange processing). j can be an agreed constant, or a function of the plaintext "byte" ordinal. Let the byte sequence number be i, then when encrypting the i-th byte, j=F(i).

(4) Decryption method:

After the ciphertext C undergoes the decryption transformation ki=D(c _i ) (i=1, 2, 3, ..., n), random sequence strings are obtained sequentially: k ₁ , k ₂ , k ₃ ,. ..., ki, ...k _n . If the ciphertext itself is composed of the above random sequences, it is not necessary to perform decryption transformation, and the strings k ₁ , k ₂ , k ₃ , ..., ki, ... k are searched in sequence in the database D _n , get its corresponding 8-bit binary number m ₁ , m ₂ , m ₃ ,..., m _n , and then convert it into plaintext information. During the decryption process, the key can be automatically updated each time a byte of plaintext is obtained through decryption. The update method is: each time the string ki is obtained from the random database to obtain the corresponding _mi , the string ki is automatically changed from the original deleted from the random sequence, and inserted into the jth position in the random sequence after deleting ki after a certain transformation (such as 0 and 1 exchange processing).

(5) Synchronous update method of database D:

Since database D is in a state of dynamic update during encryption and decryption, this update is a rearrangement of random sequences in database D, then any active attack that affects the rearrangement of random sequences in the database (such as inserting ciphertext characters , deletion or replay operation) may cause decryption interruption (as long as the uniqueness condition of the random sequence string obtained from the ciphertext is destroyed, the decryption process will automatically terminate). Suppose the original shared database between the sender and the receiver is D ₀ , after encryption, the sender’s database is updated to D ₁ , if the receiver’s decryption is successful, its database is automatically updated to D ₁ , otherwise it is not updated, and the sender is requested to resend , the sender's encrypted database is returned to D ₀ . That is to say, as long as the receiver fails to decrypt, the sender is requested to resend according to the previous database.

The cryptographic system of the present invention has the following characteristics:

1. The database D owned by both communicating parties in this cryptographic system is a small database with only 256 pieces of data, which runs very fast during the encryption and decryption process.

2. After the two parties share the database D once, the database can be automatically updated during the encryption and decryption process, and a randomization process is introduced in the update process, thus realizing the real "one-time encryption".

3. This cryptographic system completely overcomes the shortcoming that the key must be the same length as the plaintext in the previous "one-time pad" system. The distribution and management of the key is no longer a difficult problem. It only needs to build a small random sequence database, use The key distribution that encrypts every bit can be easily realized by string search and comparison tool.

4. Since this system is a "one-time pad" undecipherable system, the only way to cause damage to this system is to actively attack this system. When an attacker inserts, deletes, or replays ciphertext characters, if the ki obtained by decrypting the inserted characters does not exist in the database D, the inserted characters will not affect the correct decryption. However, when a delete or replay operation is performed, decryption may be affected. If it cannot be decrypted correctly (for example, the uniqueness of the search result is destroyed when the string ki is sequentially searched in the database D during the decryption process, or garbled characters or other meaningless information are found after the decryption is completed), it can be judged that the ciphertext has been encrypted. tamper. Therefore, this cryptographic system has the characteristics of automatically detecting whether the ciphertext has been stolen, tampered with or destroyed, and the ciphertext can be completely kept secret and cannot be counterfeited.

Description of drawings:

Figure 1: 8-bit binary database D, consisting of 256 pieces of data, A is an 8-bit binary number of 0-255, and B is a random sequence corresponding to each 8-bit binary (composed of 30-100 0s and 1s).

Figure 2: Information encryption process and method

Figure 3: Information decryption process and method

Figure 4: Method for key update

Detailed ways

First, construct the 8-bit binary database D. As shown in Figure 1, A(i) represents an 8-bit binary number from 0 to 255; B(i) represents a random sequence corresponding to it. The random sequence B(i) can be composed of any characters. In Figure 1, we assume that the random sequence is composed of 0 and 1. The setting of the sequence length is based on sufficient guarantee of the uniqueness of the random sequence ki and the operation speed of the sequence search. Since 2 ¹⁶ =65536, corresponding to 256 pieces of binary data, theoretically 256 16-bit binary random sequences can be found corresponding to each binary data. It is sufficient to set the length of each random sequence between 30-100 characters.

To encrypt a plaintext message M, first convert it into binary, and then automatically divide each byte into several units, such as m ₁ , m ₂ , m ₃ ,..., m _n . Then, search in the database D in turn, find the corresponding random sequence B(i) according to the retrieved 8-bit binary number A(i), and then randomly intercept a segment consisting of 16 characters in B(i) The sequence ki. When all the bytes of the plaintext M are transformed above, k ₁ , k ₂ , k ₃ , ..., k _n are sequentially obtained, which constitutes the ciphertext. The random sequence ki can also undergo encryption transformation Ci=E(k _i ) (i=1, 2, 3, ..., n), and finally the ciphertext C = c ₁ c ₂ c ₃ ... c _n can be obtained. The encryption transformation may be to use a 16-bit binary number K to perform XOR processing on _ki . Figure 2 shows the flow and method of information encryption.

Among them, k ₁ , k ₂ , k ₃ ,..., k _n need to meet the uniqueness condition, that is, in the database D, these random sequences ki are unique, if the intercepted ki cannot meet the uniqueness condition, it must be re- Select until the uniqueness condition is met. The random sequence database D can be dynamically updated every time a byte is encrypted. Figure 4 shows that after the ki "0101011000010100" that encrypts a binary data mi "10011010" is selected, it is deleted from the original position. The position of the 10th character of the sequence (j=10), thus changing the original random sequence corresponding to the binary data "10011010".

The method of information decryption is that after the ciphertext C undergoes decryption transformation ki=D(c _i ) (i=1, 2, 3,..., n) (the decryption transformation can be a 16-bit binary number K performs XOR processing on c _i ), and sequentially obtain random sequence strings: k ₁ , k ₂ , k ₃ , ..., ki, ... k _n . If the ciphertext itself is composed of the above random sequence ki, there is no need to perform decryption transformation, and the strings k ₁ , k ₂ , k ₃ , ..., ki, ... are sequentially searched in the database D k _n , obtain its corresponding 8-bit binary number m ₁ , m ₂ , m ₃ ,..., m _n , and convert it into plaintext information.

The random sequence database D can also be dynamically updated each time a byte is decrypted, so as to ensure that the random sequence database D is synchronized with the information sender. The dynamic update method is the same as the dynamic update method of the random sequence database D after encrypting one byte. Take Figure 4 as an example, when decrypting, look up the string ki "0101011000010100" in the random sequence database D, and get the corresponding binary data _mi "10011010", then delete ki from the original position, and then process 0 and 1 swap Afterwards, it becomes "1010100111101011", and is inserted into the position of the 10th character of the random sequence after deleting ki (j=10), so that the dynamically updated random sequence database D and the information sender have kept synchronization.

If the plaintext has 1000 bytes, then after encryption, the random sequence database D will undergo 1000 data updates. Suppose the database before encryption is D ₀ , and the database after encryption is D ₁ , then the more encrypted bytes, or after multiple rounds of information encryption, the greater the difference between D ₁ and D ₀ , so that they are completely different.

The cryptographic system can carry out information hiding. Some character strings that do not exist in the random sequence database D can be added to the ciphertext without affecting the decryption result at all.

Since the random sequence database D is composed of random sequences, and the intercepted character string ki is also randomly intercepted, the database D is automatically updated once each time a byte is encrypted, so this cryptographic system is a real "one-time pad" perfect cryptographic system , completely undecipherable.

When the attacker inserts, deletes, or replays the ciphertext characters, it may affect the decryption (if the ki obtained by decrypting the inserted characters does not exist in the database D, then the inserted characters will not affect the correct decryption) . During the decryption process, if it is found that its uniqueness in the database D is destroyed when searching for the string ki, or if garbled characters or other meaningless information are found after decryption, it can be judged that the ciphertext has been tampered with. Therefore, this cryptographic system has the characteristics of automatically detecting whether the ciphertext has been stolen, tampered with or destroyed, and the ciphertext can be completely kept secret and cannot be counterfeited.

Claims (9)

1. A cryptographic system based on a random sequence database, characterized in that it proceeds according to the following steps and methods: (1) First, build an 8-bit binary database D. The database is composed of 256 pieces of data, and each piece of data is composed of an 8-bit binary number A(i) and its corresponding random sequence B(i). (2) Encryption method: first convert the plaintext M into a binary number, and automatically divide each byte, that is, an 8-bit binary number, into several units m ₁ , m ₂ , m ₃ ,..., m _n . Then, search in the database D in turn, find the corresponding random sequence B(i) according to the retrieved 8-bit binary number A(i), and then randomly intercept a section of 16-character sequence in B(i) sequence ki. ki needs to meet the uniqueness condition, that is, in the database D, these random sequences ki are unique, if the intercepted ki cannot meet the uniqueness condition, it must be reselected until the uniqueness condition is met. To check the uniqueness of ki, you can use a string search algorithm to search in database D. If ki has only one search result, it means that ki is unique in database D, otherwise it is not unique. When all the bytes of the plaintext M are transformed above, k ₁ , k ₂ , k ₃ , ..., k _n are sequentially obtained, which constitutes the ciphertext. The random sequence ki can also undergo encryption transformation C(i)=E(k _i ) (i=1, 2, 3,...,n), and finally the ciphertext C=c ₁ c ₂ c ₃ ...c can be obtained _n . (3) Key dynamic update method: During the encryption process, the key can be automatically updated after encrypting one byte (8-bit binary number m _i ) of plaintext each time. The update method is: the random sequence corresponding to m _i After a section of subsequence ki is intercepted, it is automatically deleted from the original random sequence, and after a certain transformation (such as 0 and 1 exchange processing), it is inserted into the jth position in the random sequence after ki is deleted. (4) Decryption method: After the ciphertext C undergoes decryption transformation ki=D(c _i ) (i=1, 2, 3, ..., n), random sequence strings k ₁ , k ₂ are sequentially obtained , k ₃ ,..., k _n . If the ciphertext itself is composed of the above random sequences, it is not necessary to perform decryption transformation, and the strings k ₁ , k ₂ , k ₃ , ..., ki, ... k are searched in sequence in the database D _n , get its corresponding 8-bit binary number m ₁ , m ₂ , m ₃ ,..., m _n , and then convert it into plaintext information. (5) Synchronous update method of database D: assume that the original shared database of the sender and receiver is D ₀ , after encryption, the sender’s database is updated to D ₁ , and if the receiver’s decryption succeeds, its database is automatically updated to D ₁ , Otherwise, do not update and request the sender to resend. 2. A kind of cryptographic system based on random sequence database according to claim 1, characterized in that its secret key is composed of random sequence database D. 3. random sequence database D according to claim 2, is characterized in that this database is made up of 256 pieces of data, and each piece of data is 8 binary numbers A (i) and its corresponding random sequence B (i) constituted. B(i) can be a string consisting of 0 and 1, or any other string. 4. A cryptographic system based on a random sequence database according to claim 1, wherein the ki intercepted from the random sequence B(i) in the encryption process is randomly intercepted. 5. The ki according to claim 4, characterized in that it is unique in the random sequence database D, and the uniqueness check is to search for ki in the random sequence database D using a character string matching algorithm. 6. A kind of cryptographic system based on random sequence database according to claim 1, it is characterized in that in the encryption process, the secret key can be updated automatically after each encryption of a byte (8-bit binary number m _i ) plaintext , the update method is: after the random sequence corresponding to m _i is intercepted for a subsequence ki, it is automatically deleted from the original random sequence, and inserted into the jth position of the random sequence after deletion of ki after a certain transformation . 7. A kind of cryptographic system based on random sequence database according to claim 1, it is characterized in that in the decryption process, the secret key can be updated automatically after each decryption obtains a byte plaintext, and the method for its update is: Each time the string ki is decrypted and the corresponding _mi is searched in the random database, the string ki is automatically deleted from the original random sequence, and after a certain transformation, it is inserted into the jth random sequence after the deletion of ki position. 8. A cryptographic system based on a random sequence database according to claim 1, wherein a sequence ks that does not exist in the random sequence database D can be inserted into the ciphertext information without affecting its correct decryption. 9. A cryptographic system based on a random sequence database according to claim 1, characterized in that the random sequence database D of both information sending and receiving parties can be updated synchronously. If the ciphertext is attacked and tampered with, causing the uniqueness of ki to be destroyed, the decryption will be interrupted by itself and the information will be resent. Let the original database shared by both the sender and the receiver be D ₀ , after encryption, the sender’s database is updated to D ₁ , if the receiver’s decryption is successful, its database is automatically updated to D ₁ , otherwise it is not updated, and the sender is requested to resend , the sender's encrypted database is returned to D ₀ .

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