Digital Data Encryption Using a Proposed W-Method Based on AES and DES Algorithms

: This paper proposes a new encryption method. It combines two cipher algorithms, i.e., DES and AES, to generate hybrid keys. This combination strengthens the proposed W-method by generating high randomized keys. Two points can represent the reliability of any encryption technique. Firstly, is the key generation; therefore, our approach merges 64 bits of DES with 64 bits of AES to produce 128 bits as a root key for all remaining keys that are 15. This complexity increases the level of the ciphering process. Moreover, it shifts the operation one bit only to the right. Secondly is the nature of the encryption process. It includes two keys and mixes one round of DES with one round of AES to reduce the performance time. The W-method deals with Arabic and English texts with the same efficiency. The result showed that the proposed method performs faster and more securely when compared to standard DES and AES algorithms.


Introduction:
One of the biggest issues with the expanding usage of computers and the necessity for inter-location communication is the security of digital data 1 . Digital data must be secured to maintain its secrecy, integrity, validity, and availability to just the intended recipient. Data security before it is transferred over a network can be ensured via encryption, which encrypts data in a form that is unreadable to unauthorized parties and can only be decoded by the authorized party 2 .
The wide use of the internet leads millions of users to exchange data electronically. Therefore, the need for security and information protection becomes a paramount goal 3 . To fulfill this goal, encryption methods must be used to secure messages between sender and receiver. The advancement of technology affects day-to-day life where information exchange is vital to complete one's essential needs, most of which are carried out using the internet, such as managing finances, communication, and education. Failure to protect this information greatly harms both the client and the beneficiary; therefore, hybrid techniques are proposed to benefit from the advantages of hybridizing the suggested algorithms.
Several encryption algorithms have been used recently 4 , 5 . They can be divided into asymmetric uses a public key, and symmetric uses a private key. The asymmetric algorithms include two keys one for the encryption and the second for the decryption which can be divided into asymmetric uses a public key, and symmetric uses a private key. The asymmetric algorithms include two keys, one for encryption and the second for decryption 6 . However, the symmetric algorithm involves one key for both encryption-decryption processes. Some algorithms use public-key encryption, such as digital signature and digest message algorithms 7 , 8 . The plaintext (original message before encryption) is subjected to different replacements and transformations by the encryption method to produce encrypted text (scrambled message after encryption). Numerous encryption methods are commonly utilized in information security 9 .
Nonetheless, (AES) Advanced Encryption Standard and (DES) Data Encryption Standard use secret key encryption. DES and AES have been found as vulnerable to strong attacks, though the need to find a new method to overcome this problem becomes a necessary target.
Because it combines security, hardware, and software performance, efficiency, and flexibility, the (AES) is one of the most widely used symmetric algorithms 10 . The National Institute of Standards and Technology (NIST) developed AES, which has key lengths of 128, 192, and 256 bits, to replace DES 11 and 3DES. It accepts data with a length of 128 bits and treats it as an array of bytes, treating the data as a 4 by 4 matrix referred to as states. The number of AES rounds depends on the key length 12 and how many different transformations are applied to the states to encrypt the plaintext into ciphertext. Because of its ease of use and excellent efficiency, the AES encryption algorithm is one of the most widely used.
In contrast to other algorithms, it consumes greater computing power 13 . AES uses AddRoundKey, SubBytes, ShiftRows, and MixColumns as its four transformations, with MixColumns having the highest computational cost of the four. Multiplication and addition are the two arithmetic operations that makeup MixColumns. It is an expensive transition because using software to perform AES necessitates computer resources and slows down the encryption process 14 .
This paper uses a combination of DES and AES to obtain a high-security algorithm. W-method proposes a new hybrid key based on AES and DES to prevent attackers from getting original data. The remaining sections of this paper are organized as follows: Section 2 discusses a brief of the related work, while Section 3 describes the materials and methods of this work, specifically the AES and DES algorithms. Section 4 explains the proposed method W-Method; Section 4 discusses experimental results while comparing the performance of (AES and DES)' with the proposed method to show better results. Section 5 contains the conclusion.

Brief of Related Work:
To demonstrate the effectiveness of each technique on the same text files based on three factors: computation size, memory use, and outputs byte. The research 15 conducted a comparative analysis of encryption algorithms for data transfer on AES, DES, and RSA. The research proved that AES and DES require medium memory for implementation, but the RSA needs a large one. Both AES and DES are the best if time and memory are major factors. According to the author, future work will concentrate on the combination of those algorithms as well as ways to speed up encryption and utilize less memory.
Research on the performance assessment of cryptographic algorithms was presented by 16 . Based on time as a parameter, the author compared different cryptographic algorithms including AES and DES. On various multimedia such as video files, and texts, these various cryptography techniques are assessed. Depending on the size of the file, different files are processed at varying speeds. The authors noticed that the AES algorithm executes with a faster throughput level and less processing time than the other algorithms. The study, therefore, suggested that in the future, the effectiveness of such a combination should be evaluated for additional factors including time utilization and bit shifting.
Several studies proved that integrating algorithms can increase performance compared to original algorithms 17-19 and 20 . This paper is an attempt to combine two cryptography algorithms. This combination has shown better performance and improved the level of security. This section discusses some of these studies. The research 21 proposed a hybrid algorithm that depends on combining PRESENT and SPECK. It creates a random key space with minimum 22560 potentially unique combinations of the secret keys in order to defeat brute force attacks and improve the performance. While 22 merged Rivest, Shamira, and Adleman (RSA), AES, and MD5 hashing to generate the essential points of authentication and integrity of the ciphered data. The paper 23 combined AES and Blowfish algorithms using symmetric and asymmetric techniques. This hybrid method has increased the level of security. In addition, the only recipient can decrypt the ciphered text. Whereas 24 integrated biometrics into a cryptographic algorithm. It generates a key from a binary string that overcame the twenty percent error in identifying the iris code. This integration made identifying individuals easier a need for a central database. The research 25 stated a CARCA algorithm that combines asymmetric RSA with symmetric AES algorithms. It protects the holy Quran from the attacker by encrypting the hash digest of the gear function. The authors in 26 argue that DEA (International Data Encryption Algorithm) and International Data Encryption Algorithm (IDEA) perform faster when compared to the original DEA and IDEA. It takes a very long time for the cryptologist to decrypt the information without knowing the key, which provides a high level of security.
Some surveys, such as 27 conducted a comparison between cryptography algorithms. They proved that the combined techniques perform better with increasing the level of security. The abovementioned studies would have been more interesting if they had included the rounds of generating keys. Therefore, our paper has considered the rounds to reduce the time. In addition to adding complexity to generating keys, it strengthens the proposed algorithm against attackers.

Materials and Methods: DES and AES Algorithms
DES is considered a block cipher algorithm 28 . It is widely used and popular because using a key-symmetry encryption algorithm that is considered a standard. Because the DES is classified as unsafe, the request for a new algorithm appears, as stated in 29 . Another name for DES is the symmetry encryption standard that some researchers called; in 1972, the DES algorithm was developed at IBM 15 . This algorithm is based on the Feistel technique entirely. It was approved by the National Bureau of Standard (NBS) when the United States National Security Agency evaluated the strength of DES 9 . Using symmetric keys in both processes ciphering / deciphering is illustrated in  DES takes a fixed-length string of plaintext bits; the plaintext will convert to cipher text with the same length by many complicated operations. In the case of DES, the block size is 64 bits. The used key by the DES consists of 64 bits, but just 56 bits are used 30 , and 8 bits are used to check parity. The effective length of the key is 56 bits, and the 8th bit of the selected key is discarded 31 . This process is shown in Fig.2, while the entire cycle for ciphering / deciphering procedures by DES is shown in Fig.  3 15 . AES is considered a symmetric block cipher. For both encryption and decryption procedures, using the duplicate keys generated, the AES is like DES 32 . The main difference between AES and DES is using different sizes of keys and blocks. This means not just the 56 bits of key size and 64 and DES' block 33 . In AES, 128, 160, 192, 224, and 256 bits are chosen as the block and key size independently 34 . The AES is not dependent on Feistel structure; the input data block is initialized and processed in a similar style for each round 35 . A key length is a specified number of AES factors. The number of actual rounds is 10 when the size of the key is 128 bit, the number of actual rounds is 12 when the size of the key is 192 bit, and the number of actual rounds is 14 when the size of the key is 256 bit 36 . The actual or most common number of critical sizes is 128 bit. There are many characteristics of AES that robustness against most known attacks, compactness for a wide range of platforms such as fast coding, and simplicity of design 37 . The general structure of AES is shown in Fig. 4. the plaintext and key are 128 bits depicted as a square matrix of bytes. The used key is expanded into an array of the key that schedules words. The ordering of bytes is noted within the matrix by column 38 . The algorithm starts with a different round key stage, followed by 9 rounds of four and the tenth round of three stages. This approach is applied for both encryption and decryption procedures. The four stages are as follows 39

The Proposed W-Method
The proposed W-method has two parts, key generation, and ciphering process. Each part has a new style in the operational procedures. The basic idea of the proposed W-method is to merge the process in both parts based on DES and AES entirely. The combining process for key generation and encryption processes is the backbone of this research. W-method takes all the benefits of both DES and AES to suggest a new key generation approach. The strength of the W-method lies in combining both DES and AES algorithms to avoid defects. When complexity is added to the keys generation procedure, the strength of the cipher is increased. The complexity of the W-method is represented by using 16 keys and 8 rounds generated and applied via the mixing procedure of DES and AES.  The first key is generated by merging 64 bits of DES with 64 bits of AES to produce 128 bits as a root key for all remaining keys that are 15. All 15 keys will be generated from the mother key that is K1 by applying the shifting procedure to the right one bit only; the shifting procedure is accumulated. Each round uses two keys and applies just one round of DES and AES; therefore, 16 keys must be available at this stage. The plaintext is divided into blocks, and each block has a size of 128 bits. The input to the key generation part is 128 bit, and the output of the key generation part is 128-bit, considering many pre and post-processing steps. The general architecture of the proposed W-method is shown in Fig. 5.

Keys Generation Procedure
In this procedure, there are three stages. The first stage is converting, the second stage is blocking, and the third stage is key generation. The first stage deals with an input that is text either in Arabic or English language. This stage is found in each round because DES deals with binary form while AES deals with the Hexa form. Therefore, this stage will convert each one to another. The second stage is blocking, dividing processed input text, either binary or Hexa, into blocks; each block contains the same number of bits. All blocks are equal in size. The size of each block is 128 bits. Just one block will entire to proposed W-method at a time. The third stage is a key generation used in the encryption procedure. The principle of operation in this stage uses DES and AES to generate the mother key from merging outputs of them. The text file used as the key is uploaded and read for both DES and AES. The DES accepts 64 bit as binary input while AES accepts 128 bit as input but in Hexa form.
The generating steps in DES functions by the exception of adding 8 bit (zeros) on the left side to obtain the final output that 64 bit. In AES, the key that has a size 128 bit will be divided into left and right, and each one of them has the same size that is 64 bit. To compromise between DES and AES, the right side will be deleted and utilize the left side that has a size 64 bit. The final step in AES is applying converting procedure to convert Hexa to binary. The important notice in DES is that not to perform PC-2. The final step in this stage is to perform merging between outputs of both to produce a mother key that has a size 128 bit with binary form. The key generation is shown in Fig. 6. All 15 keys will generate from the mother key generated previously as the following operations: K2= shift one bit to the right direction of k1, K3= shift one bit to the right direction of k2, K4= shift one bit to the right direction of k3. K5= shift one bit to the right direction of k4, K6= shift one bit to the right direction of k5, K7= shift one bit to the right direction of k6. K8= shift one bit to the right direction of k7, K9= shift one bit to the right direction of k8, K10= shift one bit to the right direction of k9. K11= shift one bit to the right direction of k10, K12= shift one bit to the right direction of k11, K13= shift one bit to the right direction of k12. K14= shift one bit to the right direction of k13, K15= shift one bit to the right direction of k14, K16= shift one bit to the right direction of k15. K1 and k2 are used in round 1, K3 and k4 are used in round 2, K5 and k6 are used in round 3, K7 and k8 are used in round 4, K9 and k10 are used in round 5, K11 and k12 are used in round 6, K13 and k14 are used in round 7 and K15, and k16 are used in round 8 of proposed W-method. Pairs of keys will use in each round. It is evident that 8 rounds are needed, so 16 keys becomes essential.

Encryption Procedure
After key generation, the encryption procedure is started. To encrypt sensitive data, one must perform eight rounds. Each round uses two generated keys from the previous stage and two operations of ciphering, the first operation is applying the first round of AES, and the result will be considered plaintext to the first round of DES. This means the plaintext will encrypt double times in each round, representing the strength of the proposed method. At the same time, the complexity is presented by ciphering a plaintext sixteen times with different keys each time. In each round the processed string should be converted from Hexa to binary and binary to Hexa. Using different keys in each round increases the complexity of the cipher algorithm. DES encryption is done by using 128 bit instead 64 bit for each round. However, the PC-2 in DES is not performed to obtain 64 bit instead 56 bit. The pseudo-code of the W-method is shown in Algorithm 1:

Decryption Procedure
On the receiver side, the destination party must decrypt the received encrypted message using the same keys used in the encryption procedure since the type of encryption is a symmetric key. The decryption procedure is done by performing eight rounds on decrypted messages. To obtain an original text according to an algorithm is shown in Algorithm 2:

Results
Our method experiments show the possibility of encrypting Arabic and English texts; all special characters and spaces are encrypted. The practical application of the W-method shows the performance and implementation of DES and AES separate from the W-method, as illustrated in Fig There are many evaluation factors used to measure the performance of DES and AES compared to the W-method. Ten evaluation factors were considered. The obtained results are shown in Table 1 below, the factors are the time of ciphering, deciphering, usage of memory, effects of avalanche, security, robustness, entropy, complexity, required coding bits, and efficiency. What can be seen is that W-method shows improvement in speed, security, memory, robustness, and keys type while the inefficiency, size of keys, and coding bits Wmethod is similar to AES. Moreover, complexity is high both in the W-method and DES. The encryption time depends on three elements; the first is the size of the key, the second is the size of the plaintext block, and the third is a method of ciphering mode. In the practical experiment, the encryption time is measured in a millisecond. In general, the performance is affected by the time of encryption. The required time to recover plaintext from encrypted text is called the time of decryption. The time of encryption and decryption is shown in Table. 2.

Conclusion:
This study proposes an integration of AES-DES algorithms as means of strengthening the current ciphering process. The hybrid algorithm gives a better performance than the standard algorithms. AES and as it is merged with DES scored better on the analysis of average time because it may vary depending upon the algorithm speed. One cannot get the different times for the same input for encryption as well as decryption because of the similarity. The proposed algorithm, which is a combination of two strong encryption standards, will function as an effective and trustworthy encryption method for data. This can also employ a double-key strategy to fend off linear attacks.