An error‐control method for narrow‐band subliminal channels: How to embed more bits in a carrier
Kazukuni Kobara, Hideki Imai · Electronics and Communications in Japan (Part III Fundamental Electronic Science) · 2001
Abstract Narrow‐band subliminal channels, discovered by Simmons, yield the possibility of transmitting covert messages by embedding them in cryptographic digital data, such as (EC)DSA signatures. Embedded messages are used for transmitting important information, or are used as watermarks or imprints of the cryptographic digital data. Anyone can use or abuse these channels very easily since cryptographic digital data which are not subliminal‐free are widely used on the Internet. For example, DSA signatures are not subliminal‐free and they are widely used in various applications, such as PGP and SSH2. A narrow‐band subliminal channel can be considered as a noisy channel when a transmitter generates only a limited number of carriers (a carrier denotes a bunch of data where a covert message is embedded). We propose a way to control the bit‐error property over a narrow‐band subliminal channel, and then evaluate it. In addition, we propose how to reduce the computational cost of generating n carriers as well as a public‐key based narrow‐band subliminal channel. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 84(8): 1–10, 2001