DH-LZW: lossless data hiding in LZW compression

LZW is one of the well-known lossless compression methods. Since it has several remarkable features such that coding is simple, prior analysis on source is unnecessary, and the whole code table is not sent to its decoder, LZW is widely used in many applications. GIF, TIFF and PDF (compressing images) are good examples of them. In spite of its reputation on compression, however, few data hiding methods are directly applied to LZW itself. This may be due to few redundancies remained in losslessly compressed data: therefore there is not enough available room for data hiding. The existing methods are lossy, however, lossless approach is preferred to the lossy one. In this paper, we propose the DH-LZW method that embeds data to source data in a lossless manner. Through this paper, modifiable elements of LZW for data hiding are introduced and a way to handle them is proposed. Experiments show very promising results.