A secure and efficient outsourceable group key transfer protocol in cloud computing

Cloud computing provides robust computational power, and the customer can economically access to large amount of computing resources with a \"pay-per-use\" utility service. It also brings forth new challenges for security when customers want to securely outsource the computation of cryptographic operations to the untrusted cloud servers. Though group key transfer is a quite common scientific and engineering task, it is difficult to implement the protocol among group members, if group members are computationally weaker players. Cloud computing provides an avenue for computationally weaker players. A novel system model, with two public cloud servers and a trusted key generation center (KGC), is proposed to address the issue of group key transfer. In order to protect the sensitive information of the customers from the public cloud's learning, we design a secure group key transfer protocol based on secret sharing in cloud computing, in which both KGC and weaker group members can delegate cloud servers to compute the interpolation polynomial and the group members are able to come up with a same key. Extensive theoretical analysis and experiment results are also given to validate the practicability of our protocol.