BPCS Steganography

Any type of data can be embedded in this way, including image documents, text and audio files. These in turn may contain their own metadata. This is therefore an extremely flexible system capable of packaging an image document with its metadata and ancillary files such as transliterations, translations, and commentaries. This enables us to meet the TIITF goal.

As already stated, the embedding capacity varies with the complexity threshold set by the user. The default is 40; the maximum is 55, and the minimum is 0. A high threshold means that only a limited amount of the less significant bitplanes can be used for substitution; thus, embedding capacity is limited, but the visual quality of the vessel is unaffected to all intents and purposes. Conversely, a low threshold means that much more of the less significant bitplanes can be used for substitution; thus, embedding capacity is increased, but the visual quality of the vessel is clearly reduced.

The relationship between complexity threshold and embedding capacity for the test file (gm-1.jpg) can be determined thus:

The range between about 20 and 40 would appear to be an appropriate compromise, especially if the vessel is only to be used as a form of "full-size thumbnail"; in fact, an even lower value (higher capacity) might be advantageous if only low-quality images are to be made publicly available.

[Click on image to view at full size]

Embedding capacity vs. complexity threshold.

Note that the vessel used here lacks a visible watermark, but the addition of a watermark (for example, using the script developed for the ADIEUX Project) does not materially affect capacity. What would affect capacity would be the type of image: for example, in the case of gm-1.jpg there are large black areas, and complexity at the bitplane level is therefore quite different to, say, an image of an elaborately illuminated initial with no black surround.

Continued