Lossless Text Steganography in Compression Coding

Abstract

This work presents a novel text steganography scheme in compression domain using a lossless compression coding which called variable Huffman coding. The secret message is embedded into compression codes. The goal of the proposed scheme is covert communication by means of text files, providing high embedding capacity, improving security of the embedded secret message and reducing transmission cost. Additionally, the original text files can be reconstructed without any distortion after the embedded secret message is extracted. In the proposed scheme, each leaf of variable Huffman tree can be used to convey a secret bit at least. According to the practical application, the embedding rate for each leaf is to be increased, i.e, the embedding capacity of the proposed scheme is scalability. The secret keys are employed to generate the stego-compression-code for each leaf of variable Huffman tree to protect the embedded message. The extracting embedded message will be meaningless without the secret keys being known. Furthermore, the size of stego-compression-code is less than the size of original file plus secret message in the proposed scheme so that the transmission cost can be reduced. Additionally, experimental results show that the performance of our method is indeed superior to Chang et al.’s scheme as well as Chen and Chang’s scheme in terms of embedding capacity and transmission cost.