A Time-Based Group Key Management Algorithm Based on Proxy Re-encryption for Cloud Storage

Abstract

Users are motivated to outsource their data into the cloud for its great flexibility and economic saving. However, outsourcingdata to cloud also increases the risk of privacy leak.A straightforward method to protect the users’privacy is to encrypt the files before outsourcing.The existing group key management methods always presume that the server is trustworthy, but cloud storage applications do not meet this condition. Therefore, how to manage the group key to enable authenticated usersto access the files securely and efficientlyis still a challenging problem.In our paper, wepropose a Time-basedGroup Key Management (TGKM)algorithmforcryptographiccloud storage applications, which uses the proxy re-encryption algorithm to transfermajorcomputingtask of the group key management to the cloud server.So, the proposed TGKM scheme greatly reduces the user’s computation and storage overhead and makes full use of cloud server to achieve an efficient group key management for the cryptographic cloud storage applications.Moreover, we introduce a key seed mechanism to generate a time-based dynamic group key which effectively strengthens the cloud data security. Our security analysis and performance evaluations both show that the proposed TGKM scheme is a secure and efficient group key management protocol for the cloud storage applications with low overheads of computation and communication.