INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VO`LUME 10, ISSUE 02, FEBRUARY 2021 ISSN 2277-8616 289 IJSTR©2021 www.ijstr.org An Efficient And Secure Profile Matching Scheme For Encounter Based Mobile Social Network Fizza Abbas, Ubaidullah Rajput, Umair Ali Khan, Farwa Abbas Abstract: Mobile Social Network (MSN) is an emerging area in recent years where many users are enjoying the facilities of social network on their mobile devices. Encounter-based MSN is a type of MSN where users share a short encounter, exchange some encounter information, and communicate later with the help of the shared encounter information. Encounter-based MSN inherent most of the security and privacy issues associated with MSN. Profile matching is an important and vastly used application of MSN as well as encounter-based MSN. In profile matching, users need to share and match their private information (such as interests). A high similarity may lead to a friendship. The revelation of this private information to an attacker can pose significant threats to the user’s privacy. In encounter -based MSN, a significant issue is the secure and accurate exchange of encounter information that can be later used for verification of the encounter. This paper proposes a secure and privacy preserving profile matching mechanism for encounter- based MSN. We have proposed a secure encounter phase and a profile matching phase. During encounter phase, users share their identity along with their signed public key and encrypted interests. The public key is signed by a registration server. During the profile matching phase, users’ encrypted interests are matched, and the encrypted results are sent to respective users. The exchange of this information is in encrypted form and only legitimate user can decrypt it. To show the feasibility of the proposed scheme, the computational cost is calculated. In the end, it is observed that the proposed scheme is taking reasonable time to calculate the interests securely. Moreover, the comparison shows that proposed scheme also provides prevention from Sybil attacks, impersonation while keeping the privacy of the users intact. Index Terms— Encounter based mobile social network, Interests, Mobile social network (MSN), Privacy, Paillier cryptosystem, Profile matching, Security. ——————————  —————————— 1 INTRODUCTION HE Mobile social networks (MSN) have become popular among mobile users. MSN is a heterogeneous network in which mobile clients make social relations by matching their attributes or interests provided by user himself or mobility pattern of users. Facebook, Twitter, QQ, Twoo, and many more use context information technologies to let users exchange data and profile information to make relationships [1]. MSN has many paradigms according to the need of mobile users. These include, Proximity based mobile social network (PMSN), Location based mobile social network, and Encounter based mobile social network [1]. PMSN is a popular application nowadays [2]. In Proximity-based mobile social networking (PMSN), users communicate with each other in physical proximity such as subway stations, cinema, university and many more. These networks enable users to use MSN based application while within proximity of each other. Location-based social networks are social networks that utilizes the features of GPS to search location and broadcast respective location and other information [2]. The users of location based mobile social network are in a specific region and share the information with each other [15]. Users find POIs (point of interests) as well as make social ties based on some location. The users normally use a server (sometimes called as location-based server or LBS) that facilitates users by providing POIs based on the users’ location. In encounter based mobile social networks, users share a short encounter [3]. During this short interaction, users share some encounter information that can be later used to identify the earlier encounter. When the users are nearby each other, users' mobile equipment stores the encounter information such as common time and location. This encounter history is used to identify each other later at a server. The users find each other based on the encounter information and then struck social ties with each other. Encounter-based MSN are not only serving as a main component of missed-connection services (such as provided by craigslist) but also useful for secure communication [3]. MSN has many applications for example profile matching, wearable services, health services, location- based services and many more. Profile matchmaking is one of the applications of MSN that enables users to find and socialize with other people who have similar interests or backgrounds [2,4]. For example, two users meet with each other in a restaurant. Both can be potential friend to one another because they share a common interest, that is, the food of a restaurant. During profile matching people share their personal information but also have concern towards their privacy [5]. This is because an attacker in the vicinity may learn the private information of users. In Encounter based social networking people share same location at same time [3, 7]. Therefore, there is high probability that these people might share similar interests. For example, in a hospital people are suffering from same disease or in a musical concert two persons might share interests other than music also. In such environment, users run some profile matching protocol that compares their profiles for potential match [7]. However, attacks are possible such as Sybil attack [8]. A malicious user may run the profile matching protocol again and again with varying interest set (that eventually matches to victim). Proximity may reveal users to each other. Therefore, it is better to anonymously share encounter information initially and perform profile matching later (on a central server). Therefore, encounter-based MSN provide an ideal platform for such application. This paper proposes a protocol for privacy preserving profile matching in an encounter-based social network. We carefully design a mechanism that enable users to securely share the encounter T ————————————————  Fizza Abbas is currently working as associate professor in computer system engineering department Quaid-e-Awam UEST, Nawabshah, Pakistan, E-mail: fizza_alvi@quest.edu.pk  Ubaidullah Rajput is currently working as associate professor in computer system engineering department Quaid-e-Awam UEST, Nawabshah, Pakistan, E-mail: ubaidullah@quest.edu.pk  Umair Ali khan is currently working as Chairman and associate professor in computer system engineering department Quaid-e- Awam UEST, Nawabshah, Pakistan, E-mail: umair.khan@quest.edu.pk  Farwa Abbas received her the master's degree in communication system from Quaid-e-Awam University of Engineering, Science and Technology (Quest), Pakistan. Email: farwa.abbas09@yahoo.com