# Application of Data Image Encryption Technology in Computer Network Information Security

Authors: Li Li
Journal: Mathematical Problems in Engineering
 (2022)

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## Abstract

In order to solve the practical problem that the security of computer network information cannot be guaranteed, which seriously affects the network performance, the author proposes a public key data encryption system based on PKI. The system proposed by the author is based on the public key cryptographic algorithm RSA, including implementation of data encryption and digital signature and key distribution, an improved RSA algorithm is proposed for the slow speed of RSA. The result obtained is as follows: after reasonable selection of parameters and the use of optimized algorithms (also known as combined algorithms), the RSA algorithm is about 1.0% to 2% more efficient than the traditional algorithm, to a certain extent, the operation efficiency of the RSA algorithm is improved, and the purpose of improving the RSA algorithm is achieved. It is proved that the public key data encryption system is of great significance for modern computer network information encryption and maintaining a green and secure network environment.


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## Body

## 1. Introduction

In recent years, the Internet has penetrated more and more deeply into people’s lives due to its simplicity, convenience, and low cost, it has become the main means of the people’s information exchange [1]. The original traditional information media such as paper, film, and tape have given way to electronic media. People can inquire about information on the Internet through network portals, or exchange information on the Internet through e-mail and BBS, all of which greatly improve people’s work efficiency [2].The Internet can not only provide people with information but also make it possible to develop online e-commerce such as online shopping and online bookstores, which greatly affects people’s lives. At the same time, the emergence of e-commerce marks the expansion of the Internet from a network that mainly provides information services to the commercial field, which can attract more funds to invest in the construction of the Internet, thereby promoting the development of the network [3].The development of the network has brought unprecedented convenience to people, but also brought new challenges to people [4, 5]. A large amount of data is transmitted on the Internet every day, including web content with relatively low security requirements, emails with relatively high security requirements, and e-commerce transaction data requiring high confidentiality. All of these have put forward higher requirements for data security on the Internet [6, 7]. Due to the openness of the Internet itself, every user who surfs the Internet becomes both a beneficiary of the network and a destroyer of the network [8]. Also due to the disorder of the current Internet network, the network order is basically in an unreliable state. Therefore, it is required to perform encryption/decryption, signature/verification, and other work on the data transmitted by online users to ensure their own online security.The rapid development of computer networks has brought mankind into the information age. The transparent transmission characteristics of the network bring people a lot of conveniences and high efficiency, but at the same time, it also brings many information security problems. An important problem to be solved urgently in the development, among them, how to ensure the safe transmission of information in the network, is a very important subject of network security. Through the analysis of computer network security and cryptographic technology, it can be determined that cryptographic technology is a basic technology in information security technology, and encrypting files transmitted through the network is an effective way to ensure file security. Based on the in-depth study of the current most advanced data encryption technology, this subject proposes an application of data image encryption technology in computer network information security. The system fully combines a symmetric key encryption algorithm, a public key encryption algorithm, and data signature technology to provide a feasible operation mode for fast and safe transmission of confidential documents, and also for the establishment of a perfect and strict computer network security mechanism. Preliminary lay the foundation for practice. This network file encryption system is mainly designed for some specific departments and enterprises and has a relatively important practical application value.


## 2. Literature Review

With the vigorous development of computer networks, the increasing number of network services, and the in-depth and extensive development of e-commerce, the confidentiality, integrity, and availability of information has never been more important. Cryptography is an old and young science [9]. Say it is ancient; it is because humans used simple cryptography thousands of years ago, in order to preserve and transmit classified political and military information. But the cryptographic ideas and technologies of this period were not so much a science as an art [10] because at this time, when cryptographers design and analyze cryptographic algorithms, they mainly rely on intuition and manual calculations, and there is no strict theory as the basis.Rani and others laid the theoretical foundation of information theory, which gave birth to the new science of cryptography [11]. However, during this period, due to the restrictions of various governments, and the application of cryptography was generally limited to the government and military departments, the research on cryptography did not achieve much. Liu et al. have well summarized the previous development of cryptography, thus widely spreading the idea of cryptography [12].Kanwal et al. led a revolution in cryptography, proving for the first time that secure communication without a shared key between the sender and the receiver is possible, thus ushering in a new era of public key cryptography [13]. The cryptosystems used before this all belong to the private key cryptosystem, that is, the sender and the receiver of information use the same or similar key, and the key needs to be negotiated and transmitted before information is transmitted, as shown in Figure 1 for the data encryption system model [14, 15]. Subsequently, the first practical public key cryptosystem, RSA, was proposed. Today, RSA is still one of the most popular public key cryptosystems. At the same time, the US National Bureau of Standards (NBS) recognized the important commercial use of cryptography, so it solicited and published the US data encryption standard DES in 1977 [16]. The publication of the DES encryption standard was quickly recognized and adopted by many companies and institutions and was then widely used in many industrial and commercial fields [17]. However, with the rapid improvement of computing technology (software and hardware) and the in-depth development of cryptography research, DES was broken in 1998 [18]. In October 2000, the United States solicited the AES (Advanced Encryption Standard) cipher algorithm [19] instead of DES.Figure 1
Data encryption system model.In recent years, with the proposal and implementation of the action plan for establishing a public key infrastructure (PKI), the idea of automatic key distribution based on the PKI layered structure has also been born. This is a safer and faster automatic key distribution system [20]. In order to solve the security problem of the Internet, countries all over the world have carried out research on it for many years and initially formed a complete set of Internet security solutions, that is, the currently widely used PKI architecture. PKI architecture adopts the certificate management public key and binds the user’s public key and the user’s other identification information (such as name, e-mail, and ID number), on the Internet, verifying the user’s identity; PKI architecture combines public key cryptography and symmetric cryptography to realize automatic key management on the Internet to ensure the confidentiality and integrity of online data [21].Based on the current research, the author proposes a scheme to improve the RSA algorithm, and the scheme is based on RSA parameter selection and the optimization algorithm itself to achieve the improvement of the RSA algorithm and has been verified in the experiment: compared with the traditional RSA algorithm, the improved RSA algorithm has higher encryption speed.


## 3. Research Methods

### 3.1. Symmetric Key Encryption

The symmetric algorithm is sometimes called the traditional cryptographic algorithm, that is, the encryption key can be deduced from the decryption key, and vice versa [22]. In most symmetric algorithms, the encryption/decryption keys are the same. These algorithms are also called secret-key algorithms or single-key algorithms, which require the sender and the receiver to agree on a key before secure communication [23]. Symmetric algorithms rely on keys, and revealing the key means that anyone can encrypt/decrypt messages. As long as the communication needs to be kept secret, the key must be kept secret.Some parameters are explained as follows: M: plaintext; C: ciphertext; E: encryption algorithm; D: decryption algorithm; k: key.The encryption and decryption of the symmetric cryptographic algorithm is expressed as(1)EkM=C,(2)DkC=M.Symmetric algorithms can be divided into two categories. A class of algorithms that operate only on a single bit (sometimes a byte) in the plaintext is called a sequence algorithm or sequence cipher [24]. Another type of algorithm is to operate on a group of bits of the plaintext, these groups of bits are called blocks, and these corresponding algorithms are called block algorithms or block ciphers. Typical block lengths for modern computer cryptographic algorithms are 64 bits, 128 bits, and 256 bits.


### 3.2. Public Key Cryptography

The key to designing a public key cryptosystem is to find a suitable one-way function first, and most public key cryptosystems are established based on the difficulty of computing the inverse of a one-way function [25]. For example, the RSA system is a typical implementation based on the one-way function model.Among all the public key cryptosystems so far, the RSA system is the most famous one. This algorithm has been recommended as the public key data encryption standard by the data encryption technology subcommittee SC20 of ISO/TC97. The security of the RSA algorithm is based on a characteristic fact in number theory: combining two large prime numbers into one large number is easy, but the reverse process is very difficult. Under today’s technical conditions, whenn is large enough, in order to find d, it is extremely difficult or even impossible to find p and q corresponding to d from n through prime factorization. It can be seen that the security of RSA depends on the digit length of the large number n as the public key. In order to ensure sufficient security, it is generally believed that current personal applications need to use 384 or 512 bits of n, companies need to use 1024 bit n, and in extremely important cases, 2048 bit n.In practical applications, users can ensure the confidentiality of data transmission by using encryption and decryption. When the reverse operation is used, the data can be authenticated, at this time, the encryption is actually a digital signature, and the decryption is the verification of the signature. Considering factors such as security and a large amount of plaintext information, the HASH operation is generally performed first. See Table1 for a summary of the RSA algorithm.Table 1
Summary of the RSA algorithm.
Public keyn = p q (p, qkeep secret), e and (p-1) (q-1) coprimePrivate keyd = e-1 (mod(p-1) (q-1))EncryptionC = Me mod (n)DecryptM = Cd mod (n)


### 3.3. PKI (Public Key Infrastructure)

PKI is a public key infrastructure, which is a new security technology, it uses public key encryption technology to provide a set of security basic platforms, and users can use the services provided by the PKI platform to communicate securely.The basis for users of the PKI system to establish a secure communication trust mechanism is: any communication on the Internet that requires security services is based on the public key, and the private key is only in the hands of the other party that the communication trusts. The basis of trust is achieved through the use of public key certificates. A public key certificate is the combination of a user’s identity and the public key held by him before the combination, a trusted authority CA verifies the user’s identity, and then the certificate combines the user’s identity and the corresponding public key, and the digital sign to prove the validity of its certificate.


### 3.4. Improved RSA Algorithm

The specific description of the RSA algorithm is as follows:(1)
Arbitrarily select two different large prime numbersp and q to calculate the product n=pq,ϕn=p−1q−1(2)
Arbitrarily select a large integere that satisfies gcde,ϕn=1, and the integer e is used as the encryption key (note: the selection of e is very easy, for example, all prime numbers greater than p and q are available);(3)
The determined decryption keyd, if you know e and ϕn, it is easy to calculate d(4)
The integersn and e are made public, and d is kept secret(5)
Encrypt plaintextm (m < n is an integer) into ciphertext c, and the encryption algorithm is c=Em=memodn;(6)
Decrypt the ciphertextc into plaintext m, and the decryption algorithm is m=Dc=cdmodn;However, it is impossible to calculated from only n and e (note: not p and q). Therefore, anyone can encrypt the plaintext, but only authorized users (who know d) can decrypt the ciphertext.After analyzing the security of the RSA algorithm, the author proposes some improvements to the RSA algorithm to make it more secure and faster. First of all, there are many parameters in the RSA algorithm, the selection of these parameters directly affects the security and operation speed of the RSA algorithm, the selection of RSA parameters is very important, and the optimization of the algorithm itself is also very critical.Technically, the security of the RSA algorithm is equivalent to the difficulty of solving the inverse of the RSA one-way function. However, in practical applications, attacks are often caused by loopholes in algorithm implementation details, therefore, when using the RSA algorithm to construct a cryptosystem, in order to ensure the security of the system, each parameter must be carefully selected. RSA has three main parameters: modulusn, encryption key e, and decryption key d.In modern cryptography, a public key cryptosystem occupies an important position, as the representative of the public key cryptosystem, the RSA cryptosystem is widely used in various fields of modern information security technology. However, the power residual calculation adopted by this algorithm is time-consuming, which has always been a bottleneck restricting its wide application. Both encryption and decryption in RSA involve raising an integer to the power, modulon. If you do the exponentiation on the integer first, then modulo n, the intermediate result will be huge. Fortunately, there is a feature of modulo arithmetic that can be exploited:(3)amodn∗bmodnmodn=a∗bmodn.Thus, a modulon operation can be performed on the intermediate result, which can make the calculation practical.


### 3.5. System Structure

The integer limit that can be represented by a 32-bit computer is 64 bits, and the large prime number required in the RSA algorithm used by the author is at least 100 bits. Therefore, in the realization of this program, the first thing that comes to mind is how to store these large numbers, and how to establish the operation library of these large numbers. Generally, a large array is used to represent this large number. During operation, the array can be regarded as a binary stream, and the purpose can be achieved by different bit operations. Currently, on 32-bit systems, an array of unsigned long can be defined. Because unsigned long is 32 bits. If you want to generate a 1024-bit key, you need to set the dimension of this array to 32. Figure2 is the main flowchart of this program.Figure 2
Main program flowchart.In order to figure out how to getn, e, and d, basically the program first generates a large prime number e, then it generates a prime number q, and ensures that e and q-1 are relatively prime, and also generates a large prime number p, ensures that e and p-1 are relatively prime, and then calculate n=p∗q, after obtaining n, we compare the sizes of n and e. If e≥n then we go back to the beginning, if e<n, then n and e are successfully found. As for calculating d, can be based on formula d=e−1modp−1∗q−1. Figure 3 is a flowchart of how to get these numbers.Figure 3
GETn,e,d flowchart.So, what is the specific process ofGETe, GETq, and GETp in Figure 3, because they are all large prime numbers generated randomly, one algorithm can be used uniformly. First, randomly generate a large number, and then you can set this large number to ensure that it is large enough and odd. Then you can judge whether the number is prime or not. As for the method for judging prime numbers, the Rabin–Miller probabilistic primality test is used because only prime numbers can pass all the tests. Figure 4 roughly describes this process.Figure 4
Flowchart of generating large prime numbers.


## 3.1. Symmetric Key Encryption

The symmetric algorithm is sometimes called the traditional cryptographic algorithm, that is, the encryption key can be deduced from the decryption key, and vice versa [22]. In most symmetric algorithms, the encryption/decryption keys are the same. These algorithms are also called secret-key algorithms or single-key algorithms, which require the sender and the receiver to agree on a key before secure communication [23]. Symmetric algorithms rely on keys, and revealing the key means that anyone can encrypt/decrypt messages. As long as the communication needs to be kept secret, the key must be kept secret.Some parameters are explained as follows: M: plaintext; C: ciphertext; E: encryption algorithm; D: decryption algorithm; k: key.The encryption and decryption of the symmetric cryptographic algorithm is expressed as(1)EkM=C,(2)DkC=M.Symmetric algorithms can be divided into two categories. A class of algorithms that operate only on a single bit (sometimes a byte) in the plaintext is called a sequence algorithm or sequence cipher [24]. Another type of algorithm is to operate on a group of bits of the plaintext, these groups of bits are called blocks, and these corresponding algorithms are called block algorithms or block ciphers. Typical block lengths for modern computer cryptographic algorithms are 64 bits, 128 bits, and 256 bits.


## 3.2. Public Key Cryptography

The key to designing a public key cryptosystem is to find a suitable one-way function first, and most public key cryptosystems are established based on the difficulty of computing the inverse of a one-way function [25]. For example, the RSA system is a typical implementation based on the one-way function model.Among all the public key cryptosystems so far, the RSA system is the most famous one. This algorithm has been recommended as the public key data encryption standard by the data encryption technology subcommittee SC20 of ISO/TC97. The security of the RSA algorithm is based on a characteristic fact in number theory: combining two large prime numbers into one large number is easy, but the reverse process is very difficult. Under today’s technical conditions, whenn is large enough, in order to find d, it is extremely difficult or even impossible to find p and q corresponding to d from n through prime factorization. It can be seen that the security of RSA depends on the digit length of the large number n as the public key. In order to ensure sufficient security, it is generally believed that current personal applications need to use 384 or 512 bits of n, companies need to use 1024 bit n, and in extremely important cases, 2048 bit n.In practical applications, users can ensure the confidentiality of data transmission by using encryption and decryption. When the reverse operation is used, the data can be authenticated, at this time, the encryption is actually a digital signature, and the decryption is the verification of the signature. Considering factors such as security and a large amount of plaintext information, the HASH operation is generally performed first. See Table1 for a summary of the RSA algorithm.Table 1
Summary of the RSA algorithm.
Public keyn = p q (p, qkeep secret), e and (p-1) (q-1) coprimePrivate keyd = e-1 (mod(p-1) (q-1))EncryptionC = Me mod (n)DecryptM = Cd mod (n)


## 3.3. PKI (Public Key Infrastructure)

PKI is a public key infrastructure, which is a new security technology, it uses public key encryption technology to provide a set of security basic platforms, and users can use the services provided by the PKI platform to communicate securely.The basis for users of the PKI system to establish a secure communication trust mechanism is: any communication on the Internet that requires security services is based on the public key, and the private key is only in the hands of the other party that the communication trusts. The basis of trust is achieved through the use of public key certificates. A public key certificate is the combination of a user’s identity and the public key held by him before the combination, a trusted authority CA verifies the user’s identity, and then the certificate combines the user’s identity and the corresponding public key, and the digital sign to prove the validity of its certificate.


## 3.4. Improved RSA Algorithm

The specific description of the RSA algorithm is as follows:(1)
Arbitrarily select two different large prime numbersp and q to calculate the product n=pq,ϕn=p−1q−1(2)
Arbitrarily select a large integere that satisfies gcde,ϕn=1, and the integer e is used as the encryption key (note: the selection of e is very easy, for example, all prime numbers greater than p and q are available);(3)
The determined decryption keyd, if you know e and ϕn, it is easy to calculate d(4)
The integersn and e are made public, and d is kept secret(5)
Encrypt plaintextm (m < n is an integer) into ciphertext c, and the encryption algorithm is c=Em=memodn;(6)
Decrypt the ciphertextc into plaintext m, and the decryption algorithm is m=Dc=cdmodn;However, it is impossible to calculated from only n and e (note: not p and q). Therefore, anyone can encrypt the plaintext, but only authorized users (who know d) can decrypt the ciphertext.After analyzing the security of the RSA algorithm, the author proposes some improvements to the RSA algorithm to make it more secure and faster. First of all, there are many parameters in the RSA algorithm, the selection of these parameters directly affects the security and operation speed of the RSA algorithm, the selection of RSA parameters is very important, and the optimization of the algorithm itself is also very critical.Technically, the security of the RSA algorithm is equivalent to the difficulty of solving the inverse of the RSA one-way function. However, in practical applications, attacks are often caused by loopholes in algorithm implementation details, therefore, when using the RSA algorithm to construct a cryptosystem, in order to ensure the security of the system, each parameter must be carefully selected. RSA has three main parameters: modulusn, encryption key e, and decryption key d.In modern cryptography, a public key cryptosystem occupies an important position, as the representative of the public key cryptosystem, the RSA cryptosystem is widely used in various fields of modern information security technology. However, the power residual calculation adopted by this algorithm is time-consuming, which has always been a bottleneck restricting its wide application. Both encryption and decryption in RSA involve raising an integer to the power, modulon. If you do the exponentiation on the integer first, then modulo n, the intermediate result will be huge. Fortunately, there is a feature of modulo arithmetic that can be exploited:(3)amodn∗bmodnmodn=a∗bmodn.Thus, a modulon operation can be performed on the intermediate result, which can make the calculation practical.


## 3.5. System Structure

The integer limit that can be represented by a 32-bit computer is 64 bits, and the large prime number required in the RSA algorithm used by the author is at least 100 bits. Therefore, in the realization of this program, the first thing that comes to mind is how to store these large numbers, and how to establish the operation library of these large numbers. Generally, a large array is used to represent this large number. During operation, the array can be regarded as a binary stream, and the purpose can be achieved by different bit operations. Currently, on 32-bit systems, an array of unsigned long can be defined. Because unsigned long is 32 bits. If you want to generate a 1024-bit key, you need to set the dimension of this array to 32. Figure2 is the main flowchart of this program.Figure 2
Main program flowchart.In order to figure out how to getn, e, and d, basically the program first generates a large prime number e, then it generates a prime number q, and ensures that e and q-1 are relatively prime, and also generates a large prime number p, ensures that e and p-1 are relatively prime, and then calculate n=p∗q, after obtaining n, we compare the sizes of n and e. If e≥n then we go back to the beginning, if e<n, then n and e are successfully found. As for calculating d, can be based on formula d=e−1modp−1∗q−1. Figure 3 is a flowchart of how to get these numbers.Figure 3
GETn,e,d flowchart.So, what is the specific process ofGETe, GETq, and GETp in Figure 3, because they are all large prime numbers generated randomly, one algorithm can be used uniformly. First, randomly generate a large number, and then you can set this large number to ensure that it is large enough and odd. Then you can judge whether the number is prime or not. As for the method for judging prime numbers, the Rabin–Miller probabilistic primality test is used because only prime numbers can pass all the tests. Figure 4 roughly describes this process.Figure 4
Flowchart of generating large prime numbers.


## 4. Analysis of Results

### 4.1. System Operation Results

Test text file test txt, the text content is 1234567890test, because there may be machine factors that affect the encryption speed, the optimized RSA algorithm, and the algorithm combined with the SMM method (now called the combined algorithm for the time being). The traditional algorithm and the combined algorithm are tested three times, and the average time is used to compare the running efficiency of these algorithms. Considering the performance of the computer used in the experiment, we did not use an excessively large number to conduct the experiment, the comparison between the traditional algorithm of 40, 80, and 100-bit modulus and the combined algorithm is given below, the results are shown in Table2–4 and Figure 5.Table 2
40-bit modulus experimental results.
Operation time (select 40-bit modulo)Time required for traditional algorithm (s)Time required for combining algorithms (s)Encryption operationDecryption operationDecryption operationDecryption operationFirst2.7542.8842.6942.794The second time2.7542.9052.6942.884The second time2.7542.9142.7842.884The fourth time2.7642.9142.7042.794The fifth time2.7542.8842.6842.886Average time2.7652.8982.6942.894Table 3
Experimental results of 80-bit modulus.
Operation time (select 80-bit modulo)Time required for traditional algorithm (s)Time required for combining algorithms (s)Encryption operationDecryption operationDecryption operationDecryption operationFirst17.8951851317.63518.496The second time17.95818.50317.81518.496The second time17.88118.58217.83118.492The fourth time17.70518.50317.75918.492The fifth time17.92818.57217.82218.482Average time17.86218.53317.76218.493Table 4
Experimental results of 100-bit modulus.
Operation time (select 100-bit modulo)Time required for traditional algorithm (s)Time required for combining algorithms (s)Encryption operationDecryption operationDecryption operationDecryption operationFirst35.47439.65835.46839.588The second time35.42439.78234.58939.536The second time35.48539.69834.98639.552The fourth time35.49239.72434.76539.568The fifth time35.48539.75635.26939.562Average time35.47639.73135.08339.569Figure 5
Encryption and decryption increase efficiency on average.From the above data, it can be seen that, after reasonable selection of parameters and the use of optimized algorithms (also called combined algorithms), the RSA algorithm is about 1.0% to 2% more efficient than the traditional algorithm, which improves the operational efficiency of the RSA algorithm to a certain extent, the purpose of improving the RSA algorithm is achieved.


## 4.1. System Operation Results

Test text file test txt, the text content is 1234567890test, because there may be machine factors that affect the encryption speed, the optimized RSA algorithm, and the algorithm combined with the SMM method (now called the combined algorithm for the time being). The traditional algorithm and the combined algorithm are tested three times, and the average time is used to compare the running efficiency of these algorithms. Considering the performance of the computer used in the experiment, we did not use an excessively large number to conduct the experiment, the comparison between the traditional algorithm of 40, 80, and 100-bit modulus and the combined algorithm is given below, the results are shown in Table2–4 and Figure 5.Table 2
40-bit modulus experimental results.
Operation time (select 40-bit modulo)Time required for traditional algorithm (s)Time required for combining algorithms (s)Encryption operationDecryption operationDecryption operationDecryption operationFirst2.7542.8842.6942.794The second time2.7542.9052.6942.884The second time2.7542.9142.7842.884The fourth time2.7642.9142.7042.794The fifth time2.7542.8842.6842.886Average time2.7652.8982.6942.894Table 3
Experimental results of 80-bit modulus.
Operation time (select 80-bit modulo)Time required for traditional algorithm (s)Time required for combining algorithms (s)Encryption operationDecryption operationDecryption operationDecryption operationFirst17.8951851317.63518.496The second time17.95818.50317.81518.496The second time17.88118.58217.83118.492The fourth time17.70518.50317.75918.492The fifth time17.92818.57217.82218.482Average time17.86218.53317.76218.493Table 4
Experimental results of 100-bit modulus.
Operation time (select 100-bit modulo)Time required for traditional algorithm (s)Time required for combining algorithms (s)Encryption operationDecryption operationDecryption operationDecryption operationFirst35.47439.65835.46839.588The second time35.42439.78234.58939.536The second time35.48539.69834.98639.552The fourth time35.49239.72434.76539.568The fifth time35.48539.75635.26939.562Average time35.47639.73135.08339.569Figure 5
Encryption and decryption increase efficiency on average.From the above data, it can be seen that, after reasonable selection of parameters and the use of optimized algorithms (also called combined algorithms), the RSA algorithm is about 1.0% to 2% more efficient than the traditional algorithm, which improves the operational efficiency of the RSA algorithm to a certain extent, the purpose of improving the RSA algorithm is achieved.


## 5. Conclusion

This subject mainly studies the application of the public key cryptosystem in the network information security system, the algorithm used is the representative algorithm RSA in the public key cryptosystem. The author establishes the network information security model based on PKI, considering that the PKI technology is based on the public key cryptosystem. The public key cryptosystem meets the requirements for information security in today’s era, and the RSA algorithm in public key cryptography plays an important role in cryptography. The obtained results are as follows: an improved RSA algorithm is implemented, and the algorithm is applied in data encryption and digital signature, which improves the running speed of the system to a certain extent. A comprehensive understanding of PKI is presented. In order to meet the needs of network development, the author proposes a linear, an RSA-basedn,n-oriented group signature scheme, this scheme reduces network overhead, it also prevents blind signatures. From the current point of view, in order to meet the actual needs, digital image encryption technology will further improve the confidentiality, encryption and decryption speed, and compression ratio, at the same time, the direction of reducing the computational complexity is developed. The research on image encryption technology is still in its infancy, and there are still a lot of problems to be further explored and developed. Practice has proved that this scheme can realize the fast and secure transmission of data and information, and provides an effective means for the transmission of confidential documents on the network, so it has a good application prospect.



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*Source: 8963756-2022-07-21.xml*