 Open Access
 Total Downloads : 392
 Authors : Prerana Choudhari, Vikas Kaul, S K Narayankhedkar
 Paper ID : IJERTV3IS061214
 Volume & Issue : Volume 03, Issue 06 (June 2014)
 Published (First Online): 25062014
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
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

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 Sbox of AES algorithm and complexity is increased by using AES in Round structure. The static Sbox is made dynamic using cipher key. The inverse Sbox 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; Sbox; Round structure

INTRODUCTION
4G, the nextgeneration 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 4GLTE standard. But Kasumi is replaced by AES in 4GLTE [2]. AES represents the current recommended standard by NIST for encryptions.
Wireless 4G LTE network uses 128bit Advanced Encryption Standard (AES) and SNOW3G algorithms for integrity protection. The 128bit 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 LTESAE security. They are based on the Advanced Encryption Standard [7]. The 168bit Digital Encryption Standard or the newer Advanced Encryption Standard is used in WiMAX standards because it specifies that, overtheair 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 SHA256 for message authentication.
Then AES is used in Round structure for proposed system. The proposed algorithm generates dynamic Sbox to enhance AES algorithm. In Round structured AES, Sbox changes in every round. So, Sbox is generated ten times for each block of data. The cipher key is used to convert static Sbox into dynamic. The inverse Sbox is also changes according to the Sbox.
Analysis of algorithm is done on the basis of various parameters. The parameters are encryption time, throughput, avalanche effect, CPU usage, and memory consumed.

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 email 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.

Advance Encryption Standard
The Advanced Encryption Standard, an algorithm acts on 128bit 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.

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

Binary Phase Shift Keying
Phaseshift 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 180Â°.

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


RELATED WORK
In September 2008,in the paper[15] Sbox is made key dependent without changing its value and without changing the inverse Sbox. 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 AESDES was proposed to overcome the weaknesses of AES algorithm. This paper presented the design and implementation of a symmetrical hybrid based 128 bit key AESDES 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 Sbox into dynamic to increase the cryptographic strength of AES cipher system. In their paper
[14] they described the process of generating SBox dynamically from cipher key and finally analyze the results and experiments. In the paper [21], Julia Juremi, Ramlan Mahmod, Salasiah Sulaiman made AES Sbox key dependent to make AES stronger. Here, only the Sbox 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 Sbox and inverse Sbox dynamic.

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 Sbox 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 SHA256 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:

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

There is additional phase of making Sbox 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 Sbox.

The Sbox is rotated by that shift value.

Before sub byte stage, the static Sbox is converted into dynamic using cipher key.

The inverse Sbox is also modified after Sbox to obtain correct inverse values.
Fig2.. AES dynamic Sbox


Round AES with Dynamic Sbox 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 Sbox 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 Sbox is created hence it is called dynamic Sbox.
Fig. 3. Round AES with Dynamic Sbox


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

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 AESCBC 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 Sbox
128
656
0.008489
0.003302
Round structured AES
with dynamic Sbox
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 Sbox
128
19328
0.223669
0.195904
Round structured AES with
dynamic Sbox
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 Sbox
128
29040
0.025291
0.020151
Round structured AES with dynamic Sbox
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 Sbox
128
393728
17.58008
17.95355
Round structured AES with dynamic Sbox
256
393728
17.70852
17.6768
Fig. 7. Graphical representation of results based on encryption time on video file

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 Sbox
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 Sbox
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 Sbox
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 Sbox
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


CONCLUSION

4G networks have endtoend 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 Sbox 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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