Optical network technologies are evolving rapidly in terms of capability, security and capacity. This paper gives an understanding for the all-optical cryptography for secured fiber-optic communication. The Internet has exhibited an explosive growth over the last 20 years and is still continuing to exhibit an exponential growth. Among the different transport network technologies, because of attractive features of optical networks such as huge bandwidth, ultra-high capacity, and ability to transmit optical signals through a long distance without much signal distortion, etc., they have been considered to be the most promising option to support the brisk growth of bandwidth demand at relatively low energy consumption. An All-Optical Network (AON) [1]-[3] is a new technology that provides very high bit rates. AONs are very often considered to be the main candidate for constituting the backbone that will carry the global traffic whose volume has been growing at astounding rates that are not expected to slow down in the near future. Without the need of Optical-to-Electrical-to-Optical (O/E/O) processing at intermediate nodes. The ability to route large amounts of data and access different channels makes AON a very appealing option for providing very high rate access in Wide Area Network, Metropolitan Area Network, and even Local Area Network. Each node of the AON is equipped with an Optical Cross-Connect or an Optical Add/Drop Multiplexer, both of which are able to pass on the optical signals without O/E/O conversion, thus eliminating electrical delay. Furthermore, one of the major key factors for the development of AON is the emergence of the Wavelength Division Multiplexing technology. These led to researches oriented to all optical networking to harness more potential bandwidth from all-optical networks. In this paper, the first section discusses about security issues. The second section discusses about the proposed block diagram in optical domain which uses the chaos based secure communication and LFSR to secure the information. The third section deals with the system implementation using the Optisystem software. It gives the various design models to secure the information and simulation results for the same. The fourth section deals in detail about the security attacks in all optical network and countermeasures, to secure the information been transmitted and also the comparison with various techniques. Then the fourth chapter deals with various system performances with and without chaos masking message encryption technique and comparison for the same. Finally, the last section deals with the conclusion and future work.
A. Security Issues
Although optical networks offer numerous advantages for high data rate communications, they have unique features and requirements in terms of security and management control that distinguish them from conventional communication networks. In particular, the special characteristics and components of optical networks also bring forth a set of security challenges, accompanied by new vulnerabilities in the network [4], [5]. To provide secure and reliable AON various security issues should be considered including physical security and information security. Physical security prevents unauthorized access to network resources. Information security [1], on the other hand, prevents unauthorized access to information, and assures confidentiality and integrity of the information. Currently, most of the research efforts on AONs security are geared.
In general, fault and attack management consist of prevention, detection and reaction mechanisms. Prevention mechanisms in transparent optical networks usually include measures aimed at overcoming the physical vulnerabilities of optical components. In network security, vulnerability is a flaw or weakness that may be exploited by an attacker to carry out a security physical attack. The peculiar characteristics and behaviors of the main components considered in deployment of an AON, such as optical fibers, optical amplifiers, and optical switching nodes, make AONs vulnerable to various forms of attacks including high-power jamming, physical infrastructure attacks, denial of service, service disruption (degrades Quality of Service, tapping attacks (provides access to unauthorized users) [4], [5] which can be used for eavesdropping and traffic analysis.
Encryption is an effective way to secure a signal and enhance the confidentiality of a network in the physical layer[1]. As with the fiber-optical transmission channel, optical encryption also benefits from not generating an electro- magnetic signature, which makes it immune to electromagnetic-based attacks. Even if eavesdroppers were able to obtain a small portion of signal by tapping into the optical fiber or listening to a residue adjacent channel, no useful information can be obtained without the knowledge of the encryption key. Encryption is the process of disguising the message which is plain text from the unauthorized users. The process of transforming cipher text back into plain text is known as Decryption. There are different techniques for enhancing optical network security such as optical encryption, optical chaos-based communication, optical steganography, and using Fiber Bragg Grating. Among several techniques, optical encryption is considered as good candidate to facilitate secure communication without compromising the processing speed. Optical encryption can effectively protect the confidentiality of the physical layer network and satisfy the high-speed requirements of modern networks. Encryption and decryption have been utilized by governments and defense forces to secure much of world’s most sensitive data.
B. Proposed Secured Optical Communication System Model
This section gives the detailed study of proposed secured optical communication system. It gives two level of security first by optical LFSR and second by chaos masking message encryption technique which helps to secure the information for optical networks. The proposed block diagram in Fig. 1 explains the optical chaos based secured communication system. It consists of transmitter, receiver and the channel. The optical LFSR [6]-[8] is designed by using the shift registers and the logic gates which is used for bit scrambling also known as randomization of bits. At first level of security the input signal and the output from Optical LFSR or Pseudo Random Bit Sequence (PRBS) is XORed together. The XOR operation is used as one of the techniques for encrypting the signal which hides the signal and provide certain level of security. Further, the XORed output is treated as one of the input to chaos masking technique and other input is chaotic signal which is generated by the phase space reconstruction by using Chen Chaos [9]. The signal performs chaos masking and it is transmitted through the fiber cable for long haul communication. The chaos masking message encryption technique secure the data to be transmitted, as the chaotic signal is high-fluctuating [10] and noise like signal which is highly unpredictable to detect.
At the receiver, same chaotic signal is been generated by using the self-synchronizing property [11] of chaos-based secured communication which help them to de-mask the signal. Further, by using the XOR gate with the same Optical LFSR can get back the original signal.
C. Chaos Communication
Chaos based secured communication [10]-[13] is one method for adding security to the data. Chaos communications is one of the application of chaos theory which intends to provide security in the transmission of information performed through different communication ways. Chaotic systems provides a rich mechanism for signal design and generation, with potential applications to communications and signal processing. Because chaotic signals are typically broadband, noise-like, and difficult to predict due to its property of sensitivity to initial conditions. Initially the two states, which are very close to each other, after certain time lapse it become very different from each other. By this it is not possible to predict the form of the system with randomly high precision. It also implies that, in practice, it is not possible to determine the long-time change of a chaotic system. A particularly useful class of chaotic systems are those that possess a self-synchronization property [11].
Transmitted signal,
s(t) = c(t) + m(t) … (1)
where, c(t) - chaotic carrier, m(t)- information Signal
Received signal,
mˈ (t) = s(t) − c(t) + noise …(2)
where, c(t) - chaotic carrier, mˈ (t) - information Signal
The chaos communication is divided into three main categories i.e., Chaos masking is shown in Fig. 2 in which a message signal is masked with the chaotic signal also known as chaotic carrier and transmitted through a channel. At the receiver side same chaotic signal is generated and demasking is perform to get back the original message signal as shown in Fig. 3. The generation of chaotic signal is based on the Lorentz chaos and Chen chaos [9] which follows the theory of phase space reconstruction. This method uses the single scalar time series between the attractor dynamics and phase space topology is the most important basic method of phase space reconstruction. For reconstruction method, it uses the most practical approach that is Grassberger with Procaccia proposed GP algorithm [14].
The input bit sequence is given to LFSR which is used to generate bit scrambled output to provide security. The chaotic signal is generated by Lorentz set of equations to carry low amplitude scrambled signal. By using Chaos masking message encryption technique hides the original information signal as chaotic signal is noise like and highly unpredictable. At the receiver, using the self-synchronization [6] property it regenerates the same chaotic signal to get back the scrambled signal. The information or input bit can be retrieved by using the efficient algorithm known as Berlekamp-Massey Algorithm [1]. Figure 4. shows the output of LFSR for the input sequence given as in Table 1. which provides the security at first level by scrambling the bit where n = 6 so the LFSR output sequence is non periodic till 63 bits. The implementation of Chaos masking in MATLAB- Simulink and generated chaotic signal is shown in Fig. 5.a -5.f respectively. First level of security is achieved by using LFSR bit scrambling which is shown in Fig. 5.b for the information shown in Fig. 5.a and second level of security achieved by chaotic masking as shown in Fig. 5.d for the chaotic signal shown in Fig. 5.c. At the receiver side the recovered demasked and descrambled signal are shown in Fig. 5.e and Fig. 5.f.
Table 1
BIT SCRAMBLING USING LFSR IN SIMULINK
Clock cycle
|
Output
|
1
|
-
|
2
|
1
|
3
|
0
|
4
|
0
|
5
|
0
|
6
|
1
|
7
|
0
|
8
|
1
|
9
|
0
|
10
|
0
|
.
|
.
|
.
|
.
|
.
|
.
|
60
|
0
|
61
|
1
|
62
|
0
|
63
|
1
|