Asymmetric key based encryption and authentication for file sharing.
Volumn 3

Asymmetric key based encryption and authentication for file sharing.

Miss. Diksha Manwan , Miss. Aratrika Banerjee, Miss. Rasika Patil, Miss. Moni Gupta, Miss. Monika Meshram  , Miss. Ankita Dive

Department of C.S.E.

Jhulelal Institute of Technology,Nagpur Maharashtra

Email: Contact no.8928494721


Encryption and Authentication plays an important role in file sharing. Encryption means converting plain text into the ciphered text so that without decrypting no one is able to access it. Authentication is the process in which the user who has sent the data is verified.  Data security is the major issue in today’s world so to  secure file sharing in the internal network we use asymmetric key based encryption and authentication.


Cloud computing is the new trending model used for computing in which the internet is used for communicating and storing the data. Some of the most crucial functionalities of cloud computing is data sharing and securely storing the important data dumped into cloud. When it comes to sharing and storing of data, the users of the cloud become bit hesitant to put the data onto the cloud scaring about the confidentiality and security of the data. Due to these aspects of preserving the security and confidentiality of the data, the notion of encryption came into picture.

Here the users can encrypt their data using various encryption algorithms before help of the third Party key generators for encrypting and decrypting of data or can encrypt by themselves using various algorithms. Cloud storage is day-by-day gaining popularity. It is being utilized as core technology for various online services. The wireless technology enables use to access almost all files, emails and data for the users using their smart devices from any remote corner of the world.

Data sharing is a prime functionality in the cloud storage. The blog writers usually allow their friends to have a look or access some of the confidential files among the various files dumped in the cloud; any organization may grant their employees to access a small part of their confidential data. So here the sharing of the encrypted data with only the authentic users, who are given the rights to access it, is the challenging factor. Although users have the option of downloading the encrypted data from the cloud, decipher them, and later send them to their friends for sharing it, but this will simply lessen the impact of cloud storage. Instead the authentic users must be given the privilege of rights for accessing while data sharing with others in such a way for accessing those data directly from the server. Cloud Storage is a service where data is remotely maintained, managed, and backed up. This service is available to users over a network, which is usually the internet. It allows the user to store files online so that the user can access them from any location via the internet. While considering data privacy, we cannot rely on traditional technique of authentication, because unexpected privilege escalation will expose all data. Solution is to encrypt data before uploading to the server with user’s own key. Data sharing is again important functionality of cloud storage, because user can share data from anywhere and anytime to anyone. For example, organization may grant permission to access part of sensitive data to their employees. But challenging task is that how to share encrypted data. Traditional way is user can download the encrypted data from storage, decrypt that data and send it to share with others, but it loses the importance of cloud storage. Cryptography technique can be applied in a two major ways- one is symmetric key encryption and other is asymmetric key encryption. In symmetric key encryption, same keys are used for encryption and decryption. By contrast, in asymmetric key encryption different keys are used, public key for encryption and private key for decryption, also known as Public-key encryption. Use of Public-key encryption is a powerful mechanism for protecting the confidentiality of stored and transmitted information is more flexible for our approach. Since the decryption key should be sent via secure channel and kept secret small size is always enviable.

Need for Key Aggregation Key aggregation plays a prime role in overcoming the network overheads. On considering a scenario, where a particular user Alice wants to send an access key to her friend Bob, who wants to access some of the files. Alice has encrypted those files before uploading them onto the cloud.

Then Alice can send an aggregate key of these Corresponding secret keys of the various files using which Bob can decrypt them. Here, the load on network traffic is lowered, as the problem of sending all the corresponding keys is replaced by sending just a single aggregate key. The expenses of having a tamper proof storage are usually high. The cost of secured storage for storing these secret keys is also reduced by storing the aggregate key due to its compact  size. To protect a user’s data confidentiality, some form of access control needs to be implemented in the Cloud. Access control should allow a user to choose who can view his data and who shouldn’t. Access Control Lists(ACLs) were originally used [10], however, it was not effective as it was too coarse-grained and was not scalable; one of the primary features of the Cloud.

Protection from Privacy and Security

Attacks: We propose the definition of direct revocation system which enables the owner to directly revoke any users at any time, and formulates the security model to distinguish dishonest cloud servers and unauthorized users through User revocation model. Motives of a malicious user-to steal valuable data, to cause controversy, to get revenge, to prove intellect and to gain prestige/ are just curious. To overcome this we use Intrusion detection system which lets the owner to know about malicious user attack. It alerts the owner by sending message about the attack noticed.

Proposed plan:

  1. The admin will generate public-private key pairs for all executives and maintain user login, ID and passwords.
  2. Public keys will be distributed to all users and private keys will be stored by the admin in an encrypted form.
  3. Users will login to a website on their intranet. To compose a message they will browse a file, choose a symmetric key, and encrypt file with that key. The symmetric key will then be encrypted by using the receiver’s public key.
  4. The encrypted key and file will be coupled together in a message and sent to the receiver.
  5. If the message reaches the receiver’s inbox then the server will send an auto-generated acknowledgement message to the sender.
  6. The receivers will open their inbox to check for messages. To read a message, they will decrypt the symmetric key using their private key. The symmetric key will then be used to obtain the original file from the cipher text.

Advantages :

  1. It reduces the success of attacks
  2.  Increased security and convenience
  3. It provides digital signature


There will be a portal for the executives of the company a kind of login page. Here each user can transfer his /her files using the internal network. Because of this the distributed denial of attacks will reduce. The files send will be encrypted by the certain key and that key is also encrypted using certain algorithm. The encryption of the key which is to be send will work as digital signature. And the receiver will have to decrypt the key and then using that key he has to decrypt the file. This is how the project will work.


  2. 1983 [2]. B. Wang, S. S. M. Chow, M. Li, and H. Li S.G. Akl and P.D. Taylor, “Cryptographic Solution to a Problem of Access Control in a Hierarchy,” ACM Trans. Computer Systems,, “Storing Shared Dataon the Cloud via Security-Mediator,” in International Conference on Distributed Computing Systems IEEE, 2013.          4.  V. Goyal, O. Pandey, A. Sahai, and B. Waters, “Attribute-Based Encryption for Fine-Grained Access Control of Encrypted Data,” Proc. 13th ACM Conf. Computer and Comm. Security 2006.   5. D. Boneh and M. K. Franklin, “Identity-Based Encryption from the Weil Pairing,” in Proceedings of Advances in Cryptology ’2001. [5]. F. Guo, Y. Mu, and Z. Chen, “Identity-Based Encryption: How to Decrypt Multiple Cipher texts

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