  The paper presents a new steganographic method called RSTEG (Retransmission
Steganography), which is intended for a broad class of protocols that utilises
retransmission mechanisms. The main innovation of RSTEG is to not acknowledge a
successfully received packet in order to intentionally invoke retransmission.
The retransmitted packet carries a steganogram instead of user data in the
payload field. RSTEG is presented in the broad context of network
steganography, and the utilisation of RSTEG for TCP (Transport Control
Protocol) retransmission mechanisms is described in detail. Simulation results
are also presented with the main aim to measure and compare the steganographic
bandwidth of the proposed method for different TCP retransmission mechanisms as
well as to determine the influence of RSTEG on the network retransmissions
level.
