Merge pull request #797 from zcash/note_encryption_remove_recipient

zcash_note_encryption: remove `recipient` parameter from `Domain::note_plaintext_bytes`

Extracted from: 169782c672

CHANGELOG.md

@@ -7,6 +7,13 @@ and this library adheres to Rust's notion of
 
 ## [Unreleased]
 
+### Changed
+- The `recipient` parameter has been removed from `Domain::note_plaintext_bytes`.
+- The `recipient` parameter has been removed from `NoteEncryption::new`. Since 
+  the `Domain::Note` type is now expected to contain information about the
+  recipient of the note, there is no longer any need to pass this information
+  in via the encryption context.
+
 ## [0.2.0] - 2022-10-13
 ### Added
 - `zcash_note_encryption::Domain`:

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "zcash_note_encryption"
 description = "Note encryption for Zcash transactions"
-version = "0.2.0"
+version = "0.3.0"
 authors = [
     "Jack Grigg <jack@electriccoin.co>",
     "Kris Nuttycombe <kris@electriccoin.co>"

src/lib.rs

@@ -180,11 +180,7 @@ pub trait Domain {
     /// future crate release, once [`zcash_primitives` has been refactored].
     ///
     /// [`zcash_primitives` has been refactored]: https://github.com/zcash/librustzcash/issues/454
-    fn note_plaintext_bytes(
-        note: &Self::Note,
-        recipient: &Self::Recipient,
-        memo: &Self::Memo,
-    ) -> NotePlaintextBytes;
+    fn note_plaintext_bytes(note: &Self::Note, memo: &Self::Memo) -> NotePlaintextBytes;
 
     /// Derives the [`OutgoingCipherKey`] for an encrypted note, given the note-specific
     /// public data and an `OutgoingViewingKey`.
@@ -349,7 +345,6 @@ pub struct NoteEncryption<D: Domain> {
     epk: D::EphemeralPublicKey,
     esk: D::EphemeralSecretKey,
     note: D::Note,
-    to: D::Recipient,
     memo: D::Memo,
     /// `None` represents the `ovk = ⊥` case.
     ovk: Option<D::OutgoingViewingKey>,
@@ -358,18 +353,12 @@ pub struct NoteEncryption<D: Domain> {
 impl<D: Domain> NoteEncryption<D> {
     /// Construct a new note encryption context for the specified note,
     /// recipient, and memo.
-    pub fn new(
-        ovk: Option<D::OutgoingViewingKey>,
-        note: D::Note,
-        to: D::Recipient,
-        memo: D::Memo,
-    ) -> Self {
+    pub fn new(ovk: Option<D::OutgoingViewingKey>, note: D::Note, memo: D::Memo) -> Self {
         let esk = D::derive_esk(&note).expect("ZIP 212 is active.");
         NoteEncryption {
             epk: D::ka_derive_public(&note, &esk),
             esk,
             note,
-            to,
             memo,
             ovk,
         }
@@ -384,14 +373,12 @@ impl<D: Domain> NoteEncryption<D> {
         esk: D::EphemeralSecretKey,
         ovk: Option<D::OutgoingViewingKey>,
         note: D::Note,
-        to: D::Recipient,
         memo: D::Memo,
     ) -> Self {
         NoteEncryption {
             epk: D::ka_derive_public(&note, &esk),
             esk,
             note,
-            to,
             memo,
             ovk,
         }
@@ -412,7 +399,7 @@ impl<D: Domain> NoteEncryption<D> {
         let pk_d = D::get_pk_d(&self.note);
         let shared_secret = D::ka_agree_enc(&self.esk, &pk_d);
         let key = D::kdf(shared_secret, &D::epk_bytes(&self.epk));
-        let input = D::note_plaintext_bytes(&self.note, &self.to, &self.memo);
+        let input = D::note_plaintext_bytes(&self.note, &self.memo);
 
         let mut output = [0u8; ENC_CIPHERTEXT_SIZE];
         output[..NOTE_PLAINTEXT_SIZE].copy_from_slice(&input.0);