A 3-level re-encryption model to ensure data protection in cloud computing environments

Ensuring about the security and privacy of stored data in cloud servers is one of the most challenging issues that decrease the rate of reliability in cloud computing environments. Applying cryptography algorithms is the most common solution to enhance the reliability of cloud servers and to protect resources from possible attacks and un-predictable events. However, the security of this type of protection is affected when some users are revoked by data owner from accessing to data. Hence, an efficient and reliable re-encryption model based on multi-level cryptography has been introduced in this paper to prevent un-authorized accesses from revoked users to cloud-based resources. The main aim of the proposed model is to classify data to several levels for managing the process of re-encryption more efficient and reliable. Therefore, 3 levels of security have been defined to carry out this classification according to the security characteristics of stored data: Time-Based Level, High Risk Level, and Custom Level. The presented model has been evaluated according to three parameters: performance, security, and scalability. The evaluation process was done by establishing a simulated environment to investigate functionality of re-encryption procedure in each level of security. Functionality and security analysis of this model shows that, the reliability and efficiency of data protection process in cloud computing environments is improved considerably by using 3-level re-encryption model.