We revisit Tree-Ring Watermarking, a recent diffusion model watermarking method that demonstrates great robustness to various attacks. We conduct an in-depth study of its framework and reveal that the distribution shift unintentionally introduced by the watermarking process, apart from watermark pattern matching, contributes to its exceptional robustness. Our investigation further exposes inherent flaws in the original design, particularly in its ability to identify multiple distinct watermark keys, where distribution shift offers no advantage. Based on the preceding analysis, we propose RingID. It consists of a novel multi-channel heterogeneous watermarking approach designed to seamlessly amalgamate distinctive advantages from diverse watermarks. Moreover, coupled with a series of suggested enhancements, RingID exhibits substantial advancements in both robustness and capacity for multi-key identification.