Abstract: In wireless and wired communication, several problems are faced such as noise, security of data, distortion etc. Reliable and secure communication is demanded in modern era. Today is the world of communication, there are so many applications such as IMO, VoIP, Skype required reliable and secure communication. For secure communication various methods and techniques are used. In earlier days, only encryption was used for the purpose of security. Another term also available such as steganography and cryptography and these terms are used in computer security. At present, covert channels are used for the secure transmission of data. Covert channels are of two types such as covert timing channels and covert storage channels. Covert timing channels are those which use timing properties of some communication channel and these are designed for passing unauthorized information and they passed the information at the speed at which things happen. But these covert timing channels controls time between transmissions of packets in overt communication. Different parameters are available to measure the performance of covert timing channels such as undetectability, robustness, delay, traffic received, traffic sent and collision count. Covert timing channels play a critical role in telecommunication, defence, banking etc. But main problem occurs in these channels is noise. So this paper aims to enhance the performance of covert timing channels by comparing different networks. Covert timing channels used for the purpose of security in different applications such as VoIP, SSH. The main properties of covert timing channels are undetectability and robustness. Covert timing channels are used to avoid unauthorized access from criminals, hackers & terrorists etc. But there are some disadvantages of covert timing channels, e.g. terrorists use covert channels to coordinate their actions. This paper also discusses about applications of covert timing channels.

Keywords: Covert Timing Channels, Security, Delay.