Add SWU hash-to-curve personalizations

src/constants.rs

@@ -2,3 +2,27 @@
 
 /// $\ell^\mathsf{Orchard}_\mathsf{base}$
 pub(crate) const L_ORCHARD_BASE: usize = 255;
+
+// SWU hash-to-curve personalizations
+
+/// SWU hash-to-curve personalization
+/// This is used for the spending key base point and the nullifier base point K^Orchard
+pub const ORCHARD_PERSONALIZATION: &str = "z.cash:Orchard";
+
+/// SWU hash-to-curve personalization for the group hash for key diversification
+pub const KEY_DIVERSIFICATION_PERSONALIZATION: &str = "z.cash:Orchard-gd";
+
+/// SWU hash-to-curve personalization for the value commitment generator
+pub const VALUE_COMMITMENT_PERSONALIZATION: &str = "z.cash:Orchard-cv";
+
+/// SWU hash-to-curve personalization for the note commitment generator
+pub const NOTE_COMMITMENT_PERSONALIZATION: &str = "z.cash:Orchard-NoteCommit";
+
+/// SWU hash-to-curve personalization for the IVK commitment generator
+pub const COMMIT_IVK_PERSONALIZATION: &str = "z.cash:Orchard-CommitIvk";
+
+/// SWU hash-to-curve personalization for the Merkle CRH generator
+pub const MERKLE_CRH_PERSONALIZATION: &str = "z.cash:Orchard-MerkleCRH";
+
+/// Window size for fixed-base scalar multiplication
+pub const FIXED_BASE_WINDOW_SIZE: usize = 3;