Efficient Provably Secure Linguistic Steganography via Range Coding

Linguistic steganography involves embedding secret messages within seemingly innocuous texts to enable covert communication.Provable security, which is a long-standing goal and key motivation, has been extended to languagemodel-based steganography.Previous provably secure approaches have achieved perfect imperceptibility, measured by zero Kullback-Leibler (KL) divergence, but at the expense of embedding capacity.In this paper, we attempt to directly use a classic entropy coding method (range coding) to achieve secure steganography, and then propose an efficient and provably secure linguistic steganographic method with a rotation mechanism.Experiments across various language models show that our method achieves around 100% entropy utilization (embedding efficiency) for embedding capacity, outperforming the existing baseline methods.Moreover, it achieves high embedding speeds (up to 1554.66 bits/s on GPT-2).The code is available at github.com/ryehr/RRC_steganography.