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A Framework for Users' Privacy Preserving of Instant Messaging on Mobile Social Networks

Safi, Mohammad | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 55431 (52)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Movaghar, Ali
  7. Abstract:
  8. In recent years, mobile social networks have largely been developed and gained considerable popularity. With the development of smartphones, the growth rate of users on mobile social networks has dramatically increased, with users constantly interacting and sharing their various private and public data. Such volume of information can be used for profitable purposes and may affect the users' privacy. However, due to the limitations of smartphones and the trivial and costly encryption, entrusting the encryption to the user, both for users and for the service provider will be challenging, thus, social network providers themselves take charge that can compromise the privacy. In this dissertation, by providing a suitable framework for mobile social networks, we attempted to meet all the privacy requirements and users' needs. The Public Broadcast Encryption approach for appropriate concordance and consistency with the structure of social networks as well as the Attribute-Based Encryption due to its capability and proper implementation of the access controls policy can be good options for using on mobile social networks, however, due to the limitations of smartphones, especially low processing power and limited storage capacity, they cannot be easily accessed on these networks. In this dissertation, the proposed framework performs based on Broadcast Encryption works by applying some changes in the structure and implementation, in which some benefits of Attribute-Based Encryption are added. The essential key generation is based on the Broadcast Encryption, and how it is managed, distributed and used is similar to Attribute-Based Encryption. In this framework, access is provided by users because of the high flexibility Attribute-Based keys to apply control policies. In order to reduce the computational load of the end device, accelerate the encryption and decryption operations and reduce the amount of storage memory for keeping the encryption and decryption parameters required by the users in the end-device, in the proposed framework we outsourced some of these operations using proxies. Cloud is also used to store shared data and user preferences in the social network. Based on the results, while protecting privacy, the proposed method is accordingly more efficient than the previous ones. For the framework, two methods have been proposed, in the first method, an attempt has been made to prioritize the speed of action and reduce the user-side calculations. In addition, all the features that a user intends for others to have access to his data can be seen in one encryption and decryption key. In the second method, the proposed framework has high flexibility and the user has more freedom in creating and combining feature keys that lead to the production of new access permissions with the help of new keys. This method is also appropriate for users who have limited storage space. The design in both methods is such that in addition to maintaining and enhancing privacy it can be used in instant messaging that is commonly used by mobile phone users. In both proposed methods, data confidentiality is ensured against the social network provider and unauthorized users. Users will be able to easily perform any grouping and access policy in relation to their friends and share data. Both methods are scalable, flexible, dynamic, and lightweight. All the actions of an instant messenger on the social network, such as deleting and adding friends, sharing and accessing data, etc., will be done easily and confidentially. Comparing the proposed methods with the existing methods shows that these methods, in addition to meeting the needs of users' privacy, also have good quality and efficiency. They will also be implementable and efficient in the real world.
  9. Keywords:
  10. Privacy ; Attribute Based Encryption ; Access Control ; Broadcast Encryption ; Mobile Social Networks ; Instant Messaging

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