ABSTRACT
Exploiting Modification Direction (EMD) based data hiding achieves good stego-image quality and high security level. Recently, a section-wise EMD was proposed to enhance the embedding capacity of EMD. Later, Wang et al. introduced a switch map based multi-group EMD to further improve the embedding capacity. However, by a detail observation on the switch map in Wang et al.'s scheme, we find that more codewords with longer code-length can be put into the switch map. In this paper, we build a new switch map by Huffman code, and construct an enhanced multi-group EMD using Huffman code based switch map. Our scheme has higher embedding capacity than Wang et al.'s scheme and other EMD based data hiding methods.
ABSTRACT
Recently, Tu and Hsu proposed a secret sharing based document protecting scheme. In their scheme, a document is encrypted into n shares using Shamir's (k,n) secret sharing, where the n shares are tied in with a cover document. The document reconstruction can be accomplished by acknowledgement of any k shares and the cover document. In this work, we construct a new document protecting scheme which is extended from Tu-Hsu's work. In Tu-Hsu's approach, each inner code of secret document takes one byte length, and shares are generated from all inner codes with the computation in GF(257), where 257 is a Fermat Prime that satisfies 257 = 223+ 1. However, the share size expands when it equals to 255 or 256. In our scheme, each two inner codes of document is combined into one double-bytes inner code, and shares are generated from these combined inner codes with the computation in GF(65537) instead, where 65537 is also a Fermat Prime that satisfies 65537 = 2 24+ 1. Using this approach, the share size in our scheme can be reduced from Tu-Hsu's scheme. In addition, since the number of combined inner codes is half of the inner codes number in Tu-Hsu's scheme, our scheme is capable of saving almost half running time for share generation and document reconstruction from Tu-Hsu's scheme.
