Where $\textOrbit(B)$ is a pseudo-random integer derived from the hash of $B$ modulo the current Tide.
Coq proof script for Theorem 4.2 (Lunar Lemma) – 2,400 lines. LUNACID v2.1.4
[2] LUNACID Core Team (2024). The Elliptic Lunar Curve Specification. IACR ePrint 2024/0420 . LUNACID v2.1.4