Anti-forensic Steganography Using Multi-bit Minimum Error Replacement with Flexible Bit Location

Multi-bit minimum error replacement (MER) is a method that can embed multi-bit logo/secret data into k least-significant bits (LSBs) of cover data only introduces minimum embedding error (MEE). However, k-LSBs MER suffers from weak anti-forensics. Moreover, it is unfortunate because no literature discusses the formulations and the properties of multi-bit MEE up to this day. Therefore, this work proposes an anti-forensic steganography system using multi-bit MERs with flexible bit location (multi-bit MER_FBL) to overcome the problem of forensics. This work also illustrates the formulations and properties of MEEs in the multi-bit MER_FBL. The embedding error can be easily and determinedly evaluated using the proposed formulations and properties. The proposed multi-bit MER_FBL embeds and hides multi-bit (k-bit, k≥1) logo/secret data into any adjoining (starting with the i^th location) k-bit b_ib_i-1 ··· b_i-k+1 of cover data only introduces MEE in the range of 0 to ±(2^k-1)2^i-k; moreover, its flexible bit location enhances the embedded security as security increases as embedding location increases. As the proposed multi-bit MER_FBL can embed multi-bit logo/secret data into any adjoining bits of cover data and has high embedding capacity and high embedding quality, this method was applied for data steganography. Finally, anti-forensics of the proposed steganography system is demonstrated using the statistical attack of Chi-square analysis.