Simplified clock drift management to avoid Denial of Service attacks in cloud

Cloud servers open some known ports for communication in the network. These ports can be used for Denial of Service (DOS) attacks by malicious users, who are capable of sending repeated requests to these open ports thereby denying services to the legitimate users. Earlier mechanisms to prevent these types of attacks include the port hopping technique. In this paper, we propose a novel technique to synchronize the clocks of clients and servers in a cloud environment to have a proper port hopping to prevent open port attacks on the servers. Since the client knows the ports which are open during a particular period of time, it prevents the DOS attacks on these ports. The ports to be used for communication are generated by cascaded pseudorandom functions and seed values are shared between client and server. This enhances the security of the port sequence generation and prevents the seed being compromised. An adaptive port hopping with synchronization using clock drifts is introduced instead of the standard port hopping technique to deal with variable clock drifts. The proposed method provides a simplified and efficient way to handle clock drifts with a minimum overhead on the system when compared to the existing models.