Hiding Data in OFDM Symbols of IEEE 802.11 Networks

TL;DR

This paper introduces WiPad, a steganographic technique that embeds hidden data into the padding of IEEE 802.11 WLAN frames, achieving high bandwidth without disrupting network operations.

Contribution

The paper proposes WiPad, a novel physical layer steganography method for WLANs, with a detailed performance analysis and record-high steganographic bandwidth.

Findings

Maximum bandwidth of 1.1 Mbit/s for data frames

Maximum bandwidth of 0.44 Mbit/s for ACK frames

WiPad is the most capacious known network steganographic channel

Abstract

This paper presents a new steganographic method called WiPad (Wireless Padding). It is based on the insertion of hidden data into the padding of frames at the physical layer of WLANs (Wireless Local Area Networks). A performance analysis based on a Markov model, previously introduced and validated by the authors in [10], is provided for the method in relation to the IEEE 802.11 a/g standards. Its results prove that maximum steganographic bandwidth for WiPad is as high as 1.1 Mbit/s for data frames and 0.44 Mbit/s for acknowledgment (ACK) frames. To the authors' best knowledge this is the most capacious of all the known steganographic network channels.