Add `SpendProver::encode_proof` and `OutputProver::encode_proof`

zcash_primitives/src/sapling/prover.rs

@@ -9,7 +9,7 @@ use crate::{
         value::{NoteValue, ValueCommitTrapdoor, ValueCommitment},
         MerklePath,
     },
-    transaction::components::{Amount, GROTH_PROOF_SIZE},
+    transaction::components::{sapling::GrothProofBytes, Amount, GROTH_PROOF_SIZE},
 };
 
 use super::{Diversifier, PaymentAddress, ProofGenerationKey, Rseed};
@@ -42,6 +42,11 @@ pub trait SpendProver {
         circuit: sapling::circuit::Spend,
         rng: &mut R,
     ) -> Self::Proof;
+
+    /// Encodes the given Sapling [`SpendDescription`] proof, erasing its type.
+    ///
+    /// [`SpendDescription`]: crate::transaction::components::SpendDescription
+    fn encode_proof(proof: Self::Proof) -> GrothProofBytes;
 }
 
 /// Interface for creating Sapling Output proofs.
@@ -68,6 +73,11 @@ pub trait OutputProver {
         circuit: sapling::circuit::Output,
         rng: &mut R,
     ) -> Self::Proof;
+
+    /// Encodes the given Sapling [`OutputDescription`] proof, erasing its type.
+    ///
+    /// [`OutputDescription`]: crate::transaction::components::OutputDescription
+    fn encode_proof(proof: Self::Proof) -> GrothProofBytes;
 }
 
 /// Interface for creating zero-knowledge proofs for shielded transactions.

zcash_proofs/src/sapling/prover.rs

@@ -11,7 +11,7 @@ use zcash_primitives::{
         value::{CommitmentSum, NoteValue, TrapdoorSum, ValueCommitTrapdoor, ValueCommitment},
         Diversifier, MerklePath, Note, PaymentAddress, ProofGenerationKey, Rseed,
     },
-    transaction::components::Amount,
+    transaction::components::{sapling::GrothProofBytes, Amount, GROTH_PROOF_SIZE},
 };
 
 use crate::{OutputParameters, SpendParameters};
@@ -64,6 +64,14 @@ impl SpendProver for SpendParameters {
     fn create_proof<R: RngCore>(&self, circuit: Spend, rng: &mut R) -> Self::Proof {
         create_random_proof(circuit, &self.0, rng).expect("proving should not fail")
     }
+
+    fn encode_proof(proof: Self::Proof) -> GrothProofBytes {
+        let mut zkproof = [0u8; GROTH_PROOF_SIZE];
+        proof
+            .write(&mut zkproof[..])
+            .expect("should be able to serialize a proof");
+        zkproof
+    }
 }
 
 impl OutputProver for OutputParameters {
@@ -94,6 +102,14 @@ impl OutputProver for OutputParameters {
     fn create_proof<R: RngCore>(&self, circuit: Output, rng: &mut R) -> Self::Proof {
         create_random_proof(circuit, &self.0, rng).expect("proving should not fail")
     }
+
+    fn encode_proof(proof: Self::Proof) -> GrothProofBytes {
+        let mut zkproof = [0u8; GROTH_PROOF_SIZE];
+        proof
+            .write(&mut zkproof[..])
+            .expect("should be able to serialize a proof");
+        zkproof
+    }
 }
 
 /// A context object for creating the Sapling components of a Zcash transaction.