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Optimized OFDM Transmission of
Encrypted Image using C-Transform
Submitted To:
Er. Vijay Kumar(Guide)
Er. Sasivarnan(Co-Guide)
Submitted By:
Karanjot Singh
M.Tech 5th Sem. (ECE)
Roll No. 11127213
Department of Electronics and Communication Engineering
M.M Engineering College Maharishi Markandeshwar University
Mullana (Ambala), Haryana 133207
CONTENTS
- (^) Introduction
- (^) Literature Survey
- (^) Motivation
- (^) Formulation of Problem
- (^) Objective
- (^) Methodology
- (^) References
- (^) Cryptography is used for identification and authentication. It is done using
Chaotic logistic map theory concept.
- (^) The Cryptography technology based on chaos theory is used because it has
been developed to overcome the disadvantages present in traditional
encryption techniques.
- (^) Benefits of Cryptography:
1.) Unique Access encryption key
2.) Secure input and output
3.) Trusted & Sealed Communication
- (^) LDPC coding is use as Channel Encoder and Decoder for OFDM System.
UEP (unequal error protection) technique is use in OFDM system to transmit
the Image.
- (^) QPSK or QAM 16 are use as mapping scheme for OFDM system. Figure 1
shows block diagram of proposed model.
(Cont…)
Message/ Watermark Image Input Cover Image Input Steganography Embedding Algorithm Embedding Image For Transmission Encryption OFDM Transmitter AWGN Channel OFDM Receiver Decryption Received Embedded Image Steganography Extracting Algorithm Message/ Watermark Image Output Cover Image Output Figure 1: Basic Block Diagram of Proposed Model Transmitter Section Receiver Section (Cont…)
The two proposed Steganography algorithms are:
1.) Embedded algorithm (Tx Side)
2.) Extraction algorithm (Rx Side)
1.) Embedded algorithm (Tx Side)
The Embedded algorithm hides a secret image in a cover image using DCT
method. The embedded algorithm is used at Transmitter side and produce
embedded out image which is transmitted through system.
Message /watermark Image Input Cover Image Input Steganography Embedding Algorithm Embedding Image For Transmission Figure 2:Block Diagram of Embedded Algorithm Message /watermark Image Input Cover Image Input Steganography Embedding Algorithm Embedding Image For Transmission (Cont…)
2.) Extraction algorithm (Rx Side) Where as on other hand do vice versa and extract hidden secret (message image) image from received embedded image. Figure 3. below illustrate Extraction Block Diagram Received Embedded Image Steganography Extracting Algorithm Message Image Output Cover Image Output Figure 3:Block Diagram of Extracting Algorithm Received Embedded Image Steganography Extracting Algorithm Message Image Output Cover Image Output (Cont…)
(Cont…)
The image encryption/decryption is done using chaotic logistic maps. The
logistic map is one of the simplest and widely used chaotic maps.
The chaotic sequences/signals are like noise signals but they are completely
certain/deterministic. Introduced first in 1845 by Verhulst as a model for
the population growth of a species, it is expressed as a recurrence equation:
In this encryption scheme, a plaintext (stream) is mixed with a key stream
(generate using chaotic eq.) and the mixing process is performed by some
suitable bitwise operators (such as XOR or XNOR) and the resultant stream
is a random sequence of bits and which is completely secure. Reversible
operation is performed for decryption.
n 1 n 1 n
x rx x
………….(1)
where the parameter r belongs to the interval and determines the map
behavior, while n is the iteration number that discretizes time.
Cryptography Technique
OFDM System For Robust Image Transmission
Orthogonal frequency division multiplexing (OFDM) is a method of encoding
digital data on multiple carrier frequencies. OFDM has developed into a popular
scheme for wideband digital communication, used in applications such as Digital
Video Broadcasting, DSL Internet Access, wireless networks, power line
networks, and 4G mobile communications.
The OFDM System for Robust Image Transmission consists of following Blocks:
1.) SPIHT Coding Scheme (Source Encoder & Decoder)
2.) LDPC Coding Scheme ( Channel Encoder in UEP Mode)
3.) Mapper & De mapper Algorithms (QPSK & QAM 16)
4.) Additive Amplitude Clipping ( To Reduce PAPR )
Figure 5. shows Basic Block for this System with different Parts
(Cont…)
Reasons of using OFDM systems
- (^) OFDM is a popular scheme for wideband digital communication, used in applications.
- (^) High spectral efficiency due to nearly rectangular frequency spectrum for high numbers of sub-carriers.
- (^) Simple digital realization by using the FFT operation.
- (^) Less complex receivers due to the avoidance of ISI with a sufficiently long cyclic prefix.
- (^) Different modulation schemes can be used on individual sub-carriers which are adapted to the transmission conditions on each sub-carrier. (Cont….…)
Drawbacks of using OFDM systems
- (^) OFDM signals with high peak-to-average power ratio (PAPR) require highly linear amplifiers. Otherwise, performance degradation occurs.
- (^) More sensitive to Doppler spread than single-carrier modulated systems.
- (^) Phase noise caused by the imperfections of the transmitter and receiver oscillators influences the system performance.
- (^) Accurate frequency and time synchronization is required.
- (^) Loss in spectral efficiency due to cyclic prefix (CP). (Cont….…)
(Cont…..)
- (^) Sharma, K. and Mishra, A. Et al. (2012) suggested that first successful transmission of watermarked image Lena using OFDM technique over AWGN wireless channel by using 256-PSK modulation technique. The performance analysis of this transmission is carried out. The visual quality of non-transmitted and transmitted signed images is quantified by computing PSNR. The extraction of watermark from signed image is carried out by using Cox's algorithm. The statistical correlation parameter SIM (I, I*) and Bit Error Rate (BER) between the original and recovered watermarks are computed before and after transmission. In the second part of this experiment performance comparison of transmission of signed images is carried out by using two different modulation schemes - 16-PSK and 16-QAM. [19]
- (^) Lokeshwari, G Et al. (2012) suggested that in the recent years, internet multimedia has made life easy and at the same time added complexity in terms of security. Robust and secured transmission strategy for high-quality image is considered a great challenge. However majority of image encryption techniques do not consider reliability during transmission and this issue is considered a problem that should be handled by an efficient cryptosystem. Apart from above mentioned the design of the system should fulfil extremes of Scalability, Usability and accountability of digital data. Valuable multimedia content such as digital images, however is vulnerable to unauthorized access while in storage and during transmission over a network. For effective protection of intellectual properties like security, integrity, confidentiality of the organization's data is an important issue [15].
Motivation
- (^) In the digital world, security is an important issue, and encryption is one of the ways to ensure security.
- (^) The need to develop new encryption schemes comes from the fact that traditional encryption schemes for textual data are not suitable for multimedia data stream.
- (^) Valuable multimedia content such as digital images, however, is vulnerable to unauthorized access while in storage and during transmission over a network.
- (^) In this Dissertation the work is to be done on hybrid algorithm to transmit robust image securely over OFDM system. This work makes system reliable ,more supportive and user friendly.
Figure 6: Basic diagram of OFDM system for Image Transmission [1] (Cont…..)
Figure 7: Overview of blocks used in Proposed Model Cryptography Steganography (Cont…..)
