HiMark: Hierarchical and Controllable Multi-bit Watermarking for Large Language Models

Summary

HiMark is a multi-bit watermarking framework for LLM-generated text that embeds provenance information using hierarchical candidate control and tournament elimination during generation. Its model-agnostic detector aggregates token-level evidence to extract the watermark. In experiments, it reached 90.01% extraction accuracy under a paraphrasing attack with 32 bits embedded in a 300-token text, while maintaining text quality.