An Enhanced Encryption Algorithm for 4G Networks

An Enhanced Encryption Algorithm for 4G Networks

Prerana Choudhari1 Information Technology

Thakur College of Engg & Tech Mumbai, India

Vikas Kaul2

Information Technology Thakur College of Engg & Tech

Mumbai, India

S K Narayankhedkar3

1. College of Engg & Tech Navi Mumbai, India

   Abstract This paper, presents the design and evaluation of enhanced encryption algorithm for 4G networks. An enhancement is done by modifying the S-box of AES algorithm and complexity is increased by using AES in Round structure. The static S-box is made dynamic using cipher key. The inverse S-box is also modified accordingly. 4G simulation model is developed by using AWGN channel and BPSK modulator/demodulator. Comparison is made between AES and the enhanced system on the basis of performance evaluation based on Runtime and Throughput.

   Keywords3G; 4G; AES; S-box; Round structure

   1. INTRODUCTION

      4G, the next-generation mobile telecommunication system, is being model for increased security and reliable communication. 4G wireless networks will operate entirely on the TCP/IP, so it becomes completely IP based. This makes 4G wireless technologies different from 3G and other preceding versions [1]. The 4G systems will support both the next generation of mobile service as well as the fixed wireless networks [24].

      AES is one of the encryption techniques which are used most frequently because of its high efficiency and simplicity. It is the highly secure algorithm. Currently there are three cipher suites in 3GPP UMTS systems; including a block cipher Kasumi and two stream ciphers SNOW 3G and ZUC. These cipher suites are also used into the 4G-LTE standard. But Kasumi is replaced by AES in 4G-LTE [2]. AES represents the current recommended standard by NIST for encryptions.

      Wireless 4G LTE network uses 128-bit Advanced Encryption Standard (AES) and SNOW3G algorithms for integrity protection. The 128-bit AES algorithm is the most preferred option in the Wireless 4G LTE network because it has undergone closed observation than other encryption algorithms [4]. EEA2 or EIA2 is used in LTE-SAE security. They are based on the Advanced Encryption Standard [7]. The 168-bit Digital Encryption Standard or the newer Advanced Encryption Standard is used in WiMAX standards because it specifies that, over-the-air transmissions should be encrypted [9]. Many researchers have taken interest in the field of combining other encryption algorithms with AES. So, it can be considered as a motivational factor for further enhancement of AES.

      To enhance secure data transmission in 3G/4G, Transport Layer Security (TLS) is used here. Within TLS Advanced Encryption Standard (AES) is used for encryption. The goal of this work is to develop advanced encryption method using enhanced AES algorithm. The whole cryptographic system has been developed. This includes encryption of data, key exchange and message authentication. RSA is used for key exchange and SHA-256 for message authentication.

      Then AES is used in Round structure for proposed system. The proposed algorithm generates dynamic S-box to enhance AES algorithm. In Round structured AES, S-box changes in every round. So, S-box is generated ten times for each block of data. The cipher key is used to convert static S-box into dynamic. The inverse S-box is also changes according to the S-box.

      Analysis of algorithm is done on the basis of various parameters. The parameters are encryption time, throughput, avalanche effect, CPU usage, and memory consumed.

      1. Transport Layer Security

         TLS is a protocol created to provide authentication, confidentiality and data integrity between two communicating applications. TLS is an IETF (Internet Engineering Task Force) standard for communicating e-mail securely. Many web browsers and server applications rely on secure SSL and TLS communications. SSL and TLS are frameworks that include cryptographic protocols which are intended to provide secure communications on the Internet.

      2. Advance Encryption Standard

         The Advanced Encryption Standard, an algorithm acts on 128-bit blocks and can use a key of 128, 192 or 256 bits in length. For encryption, each round consists of the four steps: Substitute bytes, Shift rows, Mix columns, and Add round key. For decryption, each round consists of the steps: Inverse sub bytes, inverse shift rows, inverse mix columns and Add round key.

      3. AES S-box

         The Rijndael S-box is a matrix used in the Advanced Encryption Standard (AES) cryptographic algorithm. which is a substitution box and acts as a lookup table. The S-box is generated by determining the multiplicative inverse for a given number in GF (28).

      4. Binary Phase Shift Keying

         Phase-shift keying is a digital modulation scheme that modulates the phase of a reference signal and BPSK is the simplest form of phase shift keying (PSK). It uses two phases which are separated by 180°.

      5. Adaptive White Gaussian Noise

      AWGN is an Additive White Gaussian Noise and it implements AWGN channel. AWGN adds Gaussian noise to its input signal.

   2. RELATED WORK

      In September 2008,in the paper[15] S-box is made key dependent without changing its value and without changing the inverse S-box. The algorithm ensures that no trapdoor was present in the cipher and expands the keyspace to slow down attacks. In 2008, the paper[18] reviewed possible attacks on AES algorithm. The hybrid structure of AES-DES was proposed to overcome the weaknesses of AES algorithm. This paper presented the design and implementation of a symmetrical hybrid based 128 bit key AES-DES algorithm as a security enhancement for live motion image transmission. Feistel structure of AES and DES is used for the same. Razi Hosseinkhani and H. Haj Seyyed Javadi generate Dynamic S- Box using cipher key in AES Cipher System in 2012. They change static S-box into dynamic to increase the cryptographic strength of AES cipher system. In their paper

      [14] they described the process of generating S-Box dynamically from cipher key and finally analyze the results and experiments. In the paper [21], Julia Juremi, Ramlan Mahmod, Salasiah Sulaiman made AES S-box key dependent to make AES stronger. Here, only the S-box is made key- dependent without changing the value. The cryptanalysis with algebraic attack is the future work of their paper.

      In proposed system, we are increasing complexity of AES algorithm by using Round structure as well as enhancing AES algorithm by making S-box and inverse S-box dynamic.

   3. PROPOSED SYSTEM

      To overcome drawbacks of other 3G/4G cipher algorithms, AES cipher algorithm is used in the proposed system because AES is the most secure algorithm. The S-box and inverse S- box of AES algorithm is improved by making it dynamic. The traditional AES algorithm uses 128 bit input data. There are certain attacks on the AES algorithm like linear, algebraic attacks and the solution is to increase the complexity. Hence to increase the complexity, AES is used in Round structure which uses 256 bits input data.

      This work is focused on enhancement of encryption algorithm. The whole cryptographic system has been developed in this work. This includes encryption of data, key exchange and message authentication. RSA is used for key exchange and SHA-256 for message authentication. To create a 4G scenario, channel is used. The data is modulated using BPSK modulator then noise is added by AWGN. After adding noise BPSK demodulator is used for demodulation.

      The performance evaluation is done ased on parameters: Throughput, Encryption and Decryption Time.

      Fig.1. Proposed system

      A. Model development

      256 bits key length and 256 bits input data is given to the enhanced AES system. The proposed systems encryption and decryption is the same as traditional AES algorithm. The round function of encryption process is also similar as the traditional AES algorithm. The 256 bits key is divided into two parts 128 bits each. First part of 128 bits is given to the round structure and second part of 128 bits is given to the AES algorithm. The various models for developing enhanced system are as follows:

      1. Dynamic S-box Generation

         Algorithm	Bits in one block	Total no of bits	encryption time	decryption time
         AES	128	656	0.008353	0.002977
         AES with dynamic S-box	128	656	0.008489	0.003302
         Round structured AES with dynamic S-box	256	656	0.009198	0.016122

         • There is additional phase of making S-box dynamic as shown in Fig. 2.

         • The hexadecimal digits of AES key are XORed with each other and obtained number is used as the shift value to the S-box.

         • The S-box is rotated by that shift value.

         • Before sub byte stage, the static S-box is converted into dynamic using cipher key.

         • The inverse S-box is also modified after S-box to obtain correct inverse values.

         Fig2.. AES dynamic S-box

      2. Round AES with Dynamic S-box Generation

      • The Round structure of AES is used as shown in Fig. 3. Here the Input Data is split into two blocks of 128 bits each.

      • One Block is given as Input to the AES section of the System. The other Block is given as Input to the AES section of the System in the next round as per the Round structure.

      • This is done for all ten rounds respectively. These outputs are then combined together to form 256 bit block of encrypted data.

      • Dynamic S-box is applied to the Round structure of AES as shown in Fig. 3.

      • In the round structure, ten times AES is applied to the block of data hence total ten times different S-box is created hence it is called dynamic S-box.

      Fig. 3. Round AES with Dynamic S-box

   4. EXPERIMENTAL RESULTS

      The results carried out till the date is based on encryption time and throughput.

      1. Encryption time on input text file, image, audio and video file

         Time taken to encrypt same amount of data in one round of Round AES network will be much lesser than AES. If we use two rounds of Round structure, we can get more complexity than AES-CBC with same encryption time.

         Computer Configurations used are Microsoft Windows 7, Intel i5 CPU 3210M @ 2.50 GHz, 4 GB RAM and Matlab 2013a.

         For text file, plaintext.txt of 82 bytes, the number of bits is 656 and key is feistel aes key enhanced aes key.

         The results are tabulated as shown below.

         TABLE I. BASED ON ENCRYPTION TIME ON TEXT FILE

         Algorithm	Bits in one block	Total no of bits	encryption time	decryption time
         AES	128	656	0.008353	0.002977
         AES with dynamic S-box	128	656	0.008489	0.003302
         Round structured AES with dynamic S-box	256	656	0.009198	0.016122

         Fig. 4. Graphical representation of results based on encryption time on input text file

         For Image file, smiley.jpg of 2.35 KB, the number of bits is 19328 and key is feistel aes key enhanced aes key.

         TABLE II. BASED ON ENCRYPTION TIME ON IMAGE FILE

         Algorithm	Bits in one block	Total no of bits	encryption time	decryption time
         AES	128	19328	0.211753	0.195217
         AES with dynamic S-box	128	19328	0.223669	0.195904
         Round structured AES with dynamic S-box	256	19328	1.327422	1.338974

         Fig. 5. Graphical representation of results based on encryption time on image file

         For Audio file, Laser.wav of 3.54 KB, the number of bits is 29040 and key is feistel aes key enhanced aes key.

         TABLE III. BASED ON ENCRYPTION TIME ON AUDIO FILE

         Algorithm	Bits in one block	Total no of bits	encryption time	decryption time
         AES	128	29040	0.02392	0.018441
         AES with dynamic S-box	128	29040	0.025291	0.020151
         Round structured AES with dynamic S-box	256	29040	0.091021	0.095382

         Fig. 6. Graphical representation of results based on encryption time on audio file

         For Video file, composite.avi of 384 KB, the number of bits is 393728 and key is feistel aes key enhanced aes key.

         TABLE IV. BASED ON ENCRYPTION TIME ON VIDEO FILE

         Algorithm	Bits in one block	Total no of bits	encryption time	decryption time
         AES	128	393728	17.61908	17.73196
         AES with dynamic S-box	128	393728	17.58008	17.95355
         Round structured AES with dynamic S-box	256	393728	17.70852	17.6768

         Fig. 7. Graphical representation of results based on encryption time on video file

      2. Throughput on input text file, image, audio and video file.

      An encryption algorithm is required which can cope up with the speed because 3G and 4G networks works on high data rate.

      Computer Configurations used are Microsoft Windows 7, Intel i5 CPU 3210M @ 2.50 GHz, 4 GB RAM and Matlab 2013a.

      For text file, plaintext.txt of 82 bytes, the number of bits is 656 and key is feistel aes key enhanced aes key.

      TABLE I. BASED ON THROUGHPUT ON INPUT TEXT FILE

      Algorithm	Bits in one block	Total no of Blocks	Throughput (kb/sec)
      			Encryption	Decryption
      AES	128	656	78.534	220.356
      AES with dynamic S-box	128	656	77.276	198.667
      Round structured AES with dynamic S- box	256	656	71.319	40.689

      Fig. 8. Graphical representation of results based on encryption timeThroughput on inpt text file

      For Image file, smiley.jpg of 2.35 KB, the number of bits is 19328 and key is feistel aes key enhanced aes key.

      Algorithm	Bits in one block	Total no of Blocks	Throughput (kb/sec)
      			Encryption	Decryption
      AES	128	19328	91.276	99.007
      AES with dynamic S-box	128	19328	86.413	98.66
      Round structured AES with dynamic S- box	256	19328	14.56	14.434

      TABLE II. BASED ON THROUGHPUT ON IMAGE FILE

      Fig. 9.Graphical representation of results based on encryption timeThroughput on image file

      For Audio file, Laser.wav of 3.54 KB, the number of bits is 29040 and key is feistel aes key enhanced aes key.

      TABLE III. BASED ON THROUGHPUT ON AUDIO FILE

      Algorithm	Bits in one block	Total no of Blocks	Throughput (kb/sec)
      			Encryption	Decryption
      AES	128	29040	1214.046	1574.751
      AES with dynamic S-box	128	29040	1148.234	1441.119
      Round structured AES with dynamic S- box	256	29040	319.047	304.459

      Fig. 10.Graphical representation of results based on encryption timeThroughput on audio file

      For Video file, composite.avi of 384 KB, the number of bits is 393728 and key is feistel aes key enhanced aes key.

      TABLE IV. BASED ON THROUGHPUT ON VIDEO FILE

      Algorithm	Bits in one block	Total no of Blocks	Throughput (kb/sec)
      			Encryption	Decryption
      AES	128	393728	22.346	22.204
      AES with dynamic S-box	128	393728	22.396	21.93
      Round structured AES with dynamic S- box	256	393728	22.233	22.273

      Fig. 11.Graphical representation of results based on encryption timeThroughput on video file

   5. CONCLUSION

4G networks have end-to-end security issue hence a solution has to be proposed for the same using SSL/TLS. SSL/TLS SSH, VPN, or a similar mechanism should be provided for security of data. Hence TLS is used here with AES as an encryption algorithm for security. To increase the complexity of system, an AES Round structure is used. Increasing complexity will make the system attack resistant and secure data from attackers. AES is enhanced by converting static S-box into dynamic using cipher key to make cryptography more strong. Hence we have concluded from the results that, when number of bits is increased, the encryption time is increased and throughput is decreased as shown in the tables. Though encryption and decryption time is increased, the complexity of network is increased with the number of bits in one block. So this system can be used in the application where time is not the constraint. 3G and 4G requires high data transmission rate in order to send image and the proposed algorithm encrypts the data in acceptable time.

We also hope to work on reducing attacks on TLS like Renegotiation attack, Version rollback attack, Truncation attack etc. and this will be the future scope of the work.

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