Add K to GroupDigest

Author: daxpedda

elliptic-curve/src/hash2curve/group_digest.rs

@@ -3,6 +3,7 @@
 use super::{ExpandMsg, FromOkm, MapToCurve, hash_to_field};
 use crate::{CurveArithmetic, ProjectivePoint, Result};
 use group::cofactor::CofactorGroup;
+use hybrid_array::ArraySize;
 
 /// Adds hashing arbitrary byte sequences to a valid group element
 pub trait GroupDigest: CurveArithmetic
@@ -12,6 +13,11 @@ where
     /// The field element representation for a group value with multiple elements
     type FieldElement: FromOkm + MapToCurve<Output = ProjectivePoint<Self>> + Default + Copy;
 
+    /// The target security level in bits:
+    /// <https://www.rfc-editor.org/rfc/rfc9380.html#section-8.9-2.2>
+    /// <https://www.rfc-editor.org/rfc/rfc9380.html#name-target-security-levels>
+    type K: ArraySize;
+
     /// Computes the hash to curve routine.
     ///
     /// From <https://www.ietf.org/archive/id/draft-irtf-cfrg-hash-to-curve-13.html>: