Remove `esk` and `ephemeral_key` arguments from `parse_note_plaintext_without_memo_ovk`

Fixes #850


Extracted from: be89e81534

CHANGELOG.md

@@ -7,6 +7,16 @@ and this library adheres to Rust's notion of
 
 ## [Unreleased]
 
+### Changed
+- The `esk` and `ephemeral_key` arguments have been removed from 
+  `Domain::parse_note_plaintext_without_memo_ovk`. It is therefore no longer
+  necessary (or possible) to ensure that `ephemeral_key` is derived from `esk`
+  and the diversifier within the note plaintext. We have analyzed the safety of
+  this change in the context of callers within `zcash_note_encryption` and
+  `orchard`. See https://github.com/zcash/librustzcash/pull/848 and the
+  associated issue https://github.com/zcash/librustzcash/issues/802 for
+  additional detail.
+
 ## [0.3.0] - 2023-03-22
 ### Changed
 - The `recipient` parameter has been removed from `Domain::note_plaintext_bytes`.

src/lib.rs

@@ -237,8 +237,6 @@ pub trait Domain {
     fn parse_note_plaintext_without_memo_ovk(
         &self,
         pk_d: &Self::DiversifiedTransmissionKey,
-        esk: &Self::EphemeralSecretKey,
-        ephemeral_key: &EphemeralKeyBytes,
         plaintext: &NotePlaintextBytes,
     ) -> Option<(Self::Note, Self::Recipient)>;
 
@@ -654,7 +652,7 @@ pub fn try_output_recovery_with_ock<D: Domain, Output: ShieldedOutput<D, ENC_CIP
         .ok()?;
 
     let (note, to) =
-        domain.parse_note_plaintext_without_memo_ovk(&pk_d, &esk, &ephemeral_key, &plaintext)?;
+        domain.parse_note_plaintext_without_memo_ovk(&pk_d, &plaintext)?;
     let memo = domain.extract_memo(&plaintext);
 
     // ZIP 212: Check that the esk provided to this function is consistent with the esk we