Low-Tech Steganography for Covert Operations

Abstract

Text steganography, the art of concealing a secret text inside another innocuous text called the cover, is usually performed by insertion of whitespace, punctuation marks, misspelling words, or by arbitrarily capitalizing words or inserting synonyms, changing font-sizes & colors, etc. All of these have the disadvantage that they either arouse suspicion or are easily noticeable; and even lost if manually copied, i.e. handwritten. Furthermore, they are easily detectable by automated checkers. Still there are other methods which require a stego-key in order to decrypt the message. In covert intelligence operations, transmission of the stego-key may not be possible at all, more so when the message is urgent. Digital communications and Internet connectivity may also be lacking in certain situations, and the only mode of message passing available may be the exchange of handwritten text on paper; which effectively rules out text modifications like font-changes, whitespace insertion, etc. or any form of digital steganography like image/audio steganography. Finally, in almost all textsteganographic techniques, there is no provision to for the receiver to detect whether or not there is indeed any message embedded. This is very important in intelligence operations where a number of decoy text need to be sent with only one concealing the actual message. In this paper, we propose a new tool called STEGASSIST that can help the sender in generating the stego-text manually. It is a low-tech form of steganography that is especially suited to covert operations like espionage or undercover journalism. In this method, the generated cover and the stego-text are identical, or in other words, there is no cover-text. Moreover, decryption does not require a stego-key, and the stego-text may be printed or even handwritten and sent via unreliable messengers, or published, without arousing any suspicion. Finally, the received stego-text can be checked by the receiver to detect whether or not there is any actual message embedded in it.

Enhancement of Capacity, Detectability and Distortion of BMP, GIF and JPEG images with Distributed Steganography

“…using LSB requires finding the least significant bits only. Another algorithm may apply LSB plus looking for a specific colour shade like the blue less noticeable for the human eye [6], restricting the capacity, and so on. Therefore, the steganographic capacity definition in the above equation where N is the number of message-carrying symbols, a is the false alarm and D is detection probability.…”

“…When referencing BMP, it implies one bit to one pixel of the image. These are not compressed and identify the depth colour of a digital image [6]. There are other variations of BMP that use compressions named differently.…”

“…2. There are optional functions such as the Extra bitmasks to be used in conjunction with the compressed version of BMP [6]. A colour table is also aggregated into this optional structure bringing the colour pixel array, followed by the Gap1 block defining the alignment structure of the file.…”