Code-based timing Covert channel in IEEE 802.11

Steganography and Covert channels, their design and detection has been one of the most important issues in security systems and computer networks. One of the media that is used for steganography is JPEG images. The purpose of many steganography techniques in pictures is to insert more covert information in image´s pixels with few changes. One of methods in JPEG steganography is EMD (Exploiting Modification Direction). EMD tries to increase embedding efficiency which means embed more hidden bits for each change. On the other hand, due to widespread use of wireless networks, designing covert channels in these networks has also attracted a lot of attention. Local wireless networks have a high degree of randomness in the selection of back off times in their collision avoidance algorithm. This feature can be used to create covert channels. In this article, the idea of EMD method is discussed to create a covert channel in wireless networks. The goal is to achieve high throughput with high degree of security.