Expose serialization size parameters directly.

These are fixed in the specification and cannot change.
Better for dependent projects to get these numbers from
this crate than to encode them by hand.

src/lib.rs

@@ -56,7 +56,9 @@ pub mod traits;
 const _N: u32 = 256;
 const Q: u32 = 3329;
 const ZETA: u32 = 17;
-const SSK_LEN: usize = 32;
+
+/// Shared Secret Key Length for all ML-KEM variants (in bytes)
+pub const SSK_LEN: usize = 32;
 
 /// The (opaque) secret key that can be de/serialized by each party.
 #[derive(Clone, Debug, Zeroize, ZeroizeOnDrop)]
@@ -223,9 +225,13 @@ pub mod ml_kem_512 {
     const ETA2: usize = 2;
     const DU: usize = 10;
     const DV: usize = 4;
-    const EK_LEN: usize = 800;
-    const DK_LEN: usize = 1632;
-    const CT_LEN: usize = 768;
+
+    /// Serialized Encapsulation Key Length (in bytes)
+    pub const EK_LEN: usize = 800;
+    /// Serialized Decapsulation Key Length (in bytes)
+    pub const DK_LEN: usize = 1632;
+    /// Serialized Ciphertext Key Length (in bytes)
+    pub const CT_LEN: usize = 768;
 
     functionality!();
 }
@@ -253,9 +259,13 @@ pub mod ml_kem_768 {
     const ETA2: usize = 2;
     const DU: usize = 10;
     const DV: usize = 4;
-    const EK_LEN: usize = 1184;
-    const DK_LEN: usize = 2400;
-    const CT_LEN: usize = 1088;
+
+    /// Serialized Encapsulation Key Length (in bytes)
+    pub const EK_LEN: usize = 1184;
+    /// Serialized Decapsulation Key Length (in bytes)
+    pub const DK_LEN: usize = 2400;
+    /// Serialized Ciphertext Key Length (in bytes)
+    pub const CT_LEN: usize = 1088;
 
     functionality!();
 }
@@ -282,9 +292,13 @@ pub mod ml_kem_1024 {
     const ETA2: usize = 2;
     const DU: usize = 11;
     const DV: usize = 5;
-    const EK_LEN: usize = 1568;
-    const DK_LEN: usize = 3168;
-    const CT_LEN: usize = 1568;
+
+    /// Serialized Encapsulation Key Length (in bytes)
+    pub const EK_LEN: usize = 1568;
+    /// Serialized Decapsulation Key Length (in bytes)
+    pub const DK_LEN: usize = 3168;
+    /// Serialized Ciphertext Key Length (in bytes)
+    pub const CT_LEN: usize = 1568;
 
     functionality!();
 }