ShiMer, a symmetric-key text steganography scheme that hides secret bits inside fluent LLM-generated text. Using a shared secret key and a pseudorandom generator, it pseudorandomly shifts the language model's next-token probability interval to form a private distribution and samples a token according to the secret bits, so the stegotext is provably indistinguishable from the model's normal output. A reordering/merging step minimizes probability-interval splitting during decoding to accumulate entropy losslessly, yielding higher embedding capacity, better efficiency, and always-correct decoding than prior provably secure schemes (METEOR, DISCOP, iMEC).
ShiMer is a symmetric-key text steganography scheme that hides secret bits inside fluent LLM-generated text. Using a shared secret key and a pseudorandom generator, it pseudorandomly shifts the langu…