A Comprehensive Survey on Cryptography Evaluation in Mobile (MANETs)

With the rapid development in network technology new network types based on wireless communication have emerged. A large family of wireless communication networks is the Mobile Ad hoc Networks (MANETs). While MANETs mobile devices should be able to connect with each other at any time and place, the vulnerabilities of MANET structure also introduce a wide range of attacks and present new challenges for the design of security mechanism ranging from developing and implementing lightweight cryptographic primitives to designing and analyzing secure protocols. Numerous security solutions and key management schemes such as symmetric and asymmetric cryptography have been used to support MANET environment. This paper conducted survey to gain a quick knowledge of security design demand and cryptography solutions to secure MANET. This survey focused on security schemas and case studies of cryptography techniques on Ad Hoc networks. Finally, conclusions are discussed.


1.
Introduction Now days, there is a massive change in communication technology due to usage of Internet Technology and handheld devices like laptops, smart phones, sensors etc. while transmitting and accessing data from one place to another place. Using these devices data can be transmitted anytime and anywhere since these devices support wireless communication. Hence wireless network communication plays vital role in our day to day life. The Ad Hoc networks can be classified into two categories such as resource dependent and resource less networks. Resource dependent networks are defined as cellular wireless networks and infrastructure fewer networks are defined as Ad Hoc wireless networks. The Ad hoc network has ability to dynamically configure them and establish among the routers shown as in figure 1. Mobile Ad Hoc Network (MANET) is an independent set of self-organized communicating devices. The role of communicating device may be a network host or a network router. The communication between nodes through wireless links. MANETs do not maintain any fixed infrastructure and focal administration. Transmission capacity of the nodes is restricted. If any two mobile nodes are in same transmission range, one act as source and other act as destination then data can be transmitted directly from source to destination. This range is defined by the empowering technology via Zigbee, Bluetooth, Wi-Fi, and Medium Access protocols. If the source and destination nodes are not in same transmission range, intermediate nodes act as routers to transmit data from one hop to another. Therefore Mobile Ad Hoc Networks can be defined as fully distributed, autonomous, and cooperative communication networks. MANETs can be used in unreachable environments such as fire detection, monitoring ocean depth and disaster recovery, battlegrounds, group meetings where participants assembled and transfer data among them with mobile devices in conference and symposium rooms and vehicle networks etc [1][2] [3].
The major issues while designing Mobile Ad Hoc Networks are routing and providing Quality of Service (QoS). Due to the mobility nature of node and shared nature of wireless link, MANETs offering guaranteed QoS. The routing protocol also must provide certain level of QoS when required by a node during transmission. Throughput, Delay, Jitter, Bandwidth, Packet Delivery Ratio are parameters. The focus of cryptography and its basic applications in MANET will build the base for later research in security [4].
Cryptography is a Modern encryption technology it provides security of data midst of routers in Ad Hoc networks. It follows different statistical and mathematical modeling's of application or algorithms which was designed to provide security for communications. Cryptography [4] is defined as "the subdivision of cryptology in which encryption/decryption algorithms are designed, to guarantee the security and authentication of data". Cryptography algorithms classified into Symmetric and Asymmetric key. This paper conducted survey of MANET security and its implementation using cryptography; it can be better achieved with a broad knowledge. Various authors have contributed their extreme work on this area and this study focused on one-way hash functions, threshold cryptography, public key cryptography, identity-based cryptography, and signatures.
The rest of this paper is organized as follows; section II discusses about various authors contribution of security and Cryptography on MANETS. Section III Cryptographic techniques to secure MANET and demonstrates the related work in this field. Section IV contains the conclusion and future directions.

Security and Cryptography Background
Security architecture mainly focuses on security attacks, mechanisms, and services. These can be defined briefly as shown in TABLE I. Information security plays important roles it all measures taken to prevent unauthorized access whether this use takes the form of disclosure, alteration, substitution, or destruction. In this field it is a combination of processes, procedures, and systems used to ensure security services [4]. In this section a general overview of security services that applied for MANET which spread out from the traditional and well-known security services; confidentiality, authentication, integrity, availability, access control, and non-repudiation, which are defined as shown below. a) Confidentiality: It is used to control access of sensitive information to prevent unauthorization. The MANET network uses an open medium, so usually all nodes within the transmission range can obtain the data. Only one way to protect data through encryption. Otherwise, may nodes have compromised by threads [4] [5].
b) Authentication: The authentication is a service it concerned with assuring the message transmission from source to destination. However, there is no central authority in MANET, and it is very difficult to identify because of virtual connection. While confidentiality in MANET can be achieved via data encryption as mentioned before, authentication can be achieved by using textual code [6].

c)
Data Integrity: The data integrity is an important parameter in the Ad HoC networks, it destroys customer data during transmission. It can be various forms duplication, insertion, alteration, reordering, or replays. Integrity in virtual medium, because the information can be changed by the attacker that was nabbed as replay attack. Hash functions shows solution to this situation and many authors are contributed there works [7]. d) Non-repudiation: it is an action on the node confirmed and associated with the customer. Signature based techniques are validated to use in MANETS. Private keys and public keys are uses in the cryptography to transmit data. In public key cryptography, users send data using its private key. All other nodes verifies A's public key, and A cannot deny that its signature is attached to the message [8].
Attacks in the MANET can be classified into two types passive and active based upon the source of the attack as internal or external and details are described in the below table in detailed. The passive attacks deal with eavesdropping on the transmission and at the same time traffic analysis and traffic monitoring also a solution. The table 2 classifies different passive and active attacks. Impersonation [10] Sinkhole Attacks [11] The Sybil Attack [11] Denial of Service (DoS) [12] Modification of Messages [11] Replay [11] Wormhole [10] Blackhole [10] Flooding Attack [5] Routing

Cryptographic Techniques to Secure MANET
Security is plays main role in the WSN. There is a difficulty to identify which techniques are used to ensure the data transmission and which metrics are going to calculate the performance of the WSN. Cryptography is one of the techniques it is available in the form of symmetric and asymmetric. The first step may be is to choose when to use symmetric cryptography and to use asymmetric cryptography. Most of the research contributions are adopted asymmetric cryptography through RSA, digital signatures and so on in this field [11] [17]. The cryptographic techniques used in select MANET security research work are shown in " Fig. 2". The details of the encryption schemes will be covered in this section. Many cryptographic techniques can be applied in MANET.  Calculate the public Keys for the source and destination nodes 3 Each node sends its public key to the other one 4 Calculate the shared secret key in both sender and receiver nodes using the public keys 5 Encrypt the data using the symmetric algorithm and the shared secret key in all data transferring between the source and destination nodes.
The main goal of the symmetric cryptography protecting data using secret key, which is used to encrypt and decrypt while hosting and retrieve data. In this cryptography secret key plays important role, in which the role of secret is encrypt and decrypt data between clients through public or private key to establish trust shaking. This technique is efficient than asymmetric in computational standpoint. More number of contributions are available and implemented different techniques and security solutions applied on the MANETs. Based on most of the contributed symmetric approaches are Random Nonce [9], Shared Key [12] and HMAC message Authentication [19].
Asymmetric cryptography is also called as public key cryptography and at the same time it is a combination of public key and private key, these are mentioned before. The private key is used to kept private data and public key can be public to the others. The well-known public key cryptographic techniques are the well-known DH and RSA algorithms, which were coming from 1970. Later many kinds of algorithms and techniques were implemented in the previous literature, such as digital signature, key management, and other techniques have been developed. In the public key cryptography, such as the El Gamal cryptograph system, DSA, and ECC. The asymmetric cryptography approaches are Diffie-Hellman [16], Digital Signature Based on RSA/DSA [20] [11], Identity-Based Cryptography (IBC) [21] [22], Elliptic Curve Cryptography [13], Threshold and Identity-Based Cryptography [23] [24], Hash Chain [25] [26], Hybrid Cryptosystems [27].

Symmetric vs Asymmetric Encryption
Many studies have compared asymmetric and symmetric encryptions based on properties of computational overhead, their simplicity of distributions. The symmetric encryption is faster than asymmetric encryption, so which consumes less CPU cycles when compare the asymmetric, Thus, from a speed point of view, symmetric is efficient than asymmetric encryption schemes. Even though, symmetric encryption generally has a many disadvantage. Here same key is used to encrypt and decrypt data while secure transmission [16]. The issue of securing symmetric key distribution becomes even more critical when the environment used for data transferring is vulnerable to security attacks. However, the asymmetric key encryption ensures private key secret, no one would be able to decrypt data. So, the public key can be easily distributed without worrying about the possibility of capturing it [29].

Related Work
This section discusses about various works on evaluation cryptography techniques performance on WSN. To protect MANET nodes from the attacker and the combination of robustness and enforcement methods are consider to more accurate methods. Many contributions are implemented distribution and lightweight methods to establish the trust between nodes without prior knowledge of the nodes [30]. In this section we will overview some research contributions in this field which applied to the different network layers of a MANET, and their primary goal is to protect or enforce the two basic functions.
Ahmad, at al. [1] and Mandal in [34] have conducted the complete analysis study of DES and conducted experiments using NS-2 simulator in terms of QoS metrics like of energy consumption, data transfer time, Endto-End delay time and throughput with varying data sizes. As per the simulation results the superiority of AES over DES performance metrics. So, the authors are recommended AES for their experiment. Ezeofor and Ulasi in [31] Jeeva, et al. [32] and presented an analysis of the most common data encryption algorithms DES, AES, Blowfish and RSA th at can be used in digital communication systems, where the data can be read, altered or forged by many types of attacks through unsecured paths. Abdul, et al. [33] and Singh and Maini in [37] provided an evaluation of six of the most common encryption algorithms: AES (Rijndael), DES, 3DES, RC2, Blowfish, and Rivest Cipher 6 (RC6). The comparison was done using different sizes and types of data blocks, different key size and different packet sizes.
Thakur and Kumar in [39] conducted comparison of different cryptography algorithms in the data encryption. They compared DES, Blowfish and AES with sleeted performance metrics to identify them. These are compared by behavioue and performance of the algorithms. The experiment was tested with different loads and different sizes of data. The algorithms were evaluated in terms of accuracy and time of encryption and decryption. The presented simulation results showed that Blowfish had a better performance than DES and AES encryption algorithms Mandal, et al. [40] discussed same works. Elminaam, et al. [41] and Nie, et al. [43] provided a comparison between the symmetric key encryption algorithms: DES, AES, and Blowfish using different data loads and conducted comprehensive survey. The simulation done using the provided classes in java environment to implement DES, AES and Blowfish. The simulation parameters were: speed, block size, and key size. Finally, the chosen metrics used to compare the performance of the algorithms were the algorithm's speed to encrypt and decrypt data blocks of various sizes.
Nadeem, and Javed in [42] evaluated and compared different encryption algorithms like DES, 3DES, AES and Blowfish. The performance of these algorithms compared by input file with different content of sizes on different hardware . Norouzi, et al. [46] implemented security algorithm in Ad hoc networks with predefined transmission rate. This experiment was simulated using MATLAB. Meanwhile for the second method data transmitted with three encryption algorithms: DES, AES and Blowfish. Thenmozhi and Madheswaran in [47] proposed a new method for different encryption algorithms (DES, AES, Blowfish and RC2) selection during processing of each packet instead of using a single encryption algorithm. The performance had been measured through simulation studies on NS-2.
Matin, et al., [48] and Elminaam et al., [49] examined the performance of a new cipher in MANET and wireless LAN networks and make a performance comparison with that of AES. The new proposed algorithm uses 200 bits key and its' performance had been evaluated algorithm in real network scenarios. Generally, a lot of researches have been done on evaluating the performance of some cryptographic mechanisms and encryption schemes to raise the data confidentiality in Table 4 we summarized the contributions in this field that we already detailed in this section.

Conclusions and future directions
Security of Ad Hoc networks is one of the research topics in the advanced technology updates. As per the previous literatures [56][57] [58] cryptography is one of the solutions to provide security in MANETs. It reduce the computation cost, improving security and improving key management techniques. This paper conducted survey on the security and cryptography issues in MANETs. The objective of this paper can be twofold, preventing different types of attacks and cryptography implementation in MANETs. We are classified attacks into two types active and passive and explained with internal and external details. Second part of this paper discussed about cryptography and its implementation on MANETS. The cryptographic techniques always play a major role in the design of each stage of the key management. The security solution applied for MANET will always be under spot by the research community and the new design will come out quickly and easily reusable as popular design patterns using cryptography terminologies [58]. Finally identified few most relevant contributions to compare with existing literatures. DES, Blowfish, AES are most frequently used cryptography algorithms in the MANET security.