(cleanup) Make the internals of `zip32::DiversifierKey` private

zcash_primitives/CHANGELOG.md

@@ -17,7 +17,8 @@ and this library adheres to Rust's notion of
   - `ExtendedSpendingKey::{from_bytes, to_bytes}`
 - Added in `zcash_primitives::zip32`
   - `ChainCode::as_bytes`
-  - `DiversifierIndex::as_bytes`
+  - `DiversifierKey::{from_bytes, as_bytes}`
+  - `DiversifierIndex::{as_bytes}`
   - `ExtendedSpendingKey::{from_bytes, to_bytes}`
   - Implementations of `From<u32>` and `From<u64>` for `DiversifierIndex`
 
@@ -27,6 +28,8 @@ and this library adheres to Rust's notion of
 - The signature of `zcash_primitives::sapling::Note::nf` has changed to
   take just a `NullifierDerivingKey` (the only capability it actually required)
   rather than the full `ViewingKey` as its first argument.
+- Made the internals of `zip32::DiversifierKey` private; use `from_bytes` and
+  `as_bytes` on this type instead.
 
 ## [0.7.0] - 2022-06-24
 ### Changed

zcash_primitives/src/sapling/keys.rs

@@ -233,7 +233,7 @@ impl DiversifiableFullViewingKey {
     pub fn from_bytes(bytes: &[u8; 128]) -> Option<Self> {
         FullViewingKey::read(&bytes[..96]).ok().map(|fvk| Self {
             fvk,
-            dk: zip32::DiversifierKey(bytes[96..].try_into().unwrap()),
+            dk: zip32::DiversifierKey::from_bytes(bytes[96..].try_into().unwrap()),
         })
     }
 
@@ -243,7 +243,7 @@ impl DiversifiableFullViewingKey {
         self.fvk
             .write(&mut bytes[..96])
             .expect("slice should be the correct length");
-        bytes[96..].copy_from_slice(&self.dk.0);
+        bytes[96..].copy_from_slice(&self.dk.as_bytes()[..]);
         bytes
     }
 

zcash_primitives/src/zip32.rs

@@ -179,7 +179,7 @@ impl DiversifierIndex {
 
 /// A key used to derive diversifiers for a particular child key
 #[derive(Clone, Copy, Debug, PartialEq)]
-pub struct DiversifierKey(pub [u8; 32]);
+pub struct DiversifierKey([u8; 32]);
 
 impl DiversifierKey {
     pub fn master(sk_m: &[u8]) -> Self {