Add methods to ProposedTransaction and description builders to build …

…zk circuits

ironfish-rust/src/transaction/mints.rs

@@ -58,17 +58,25 @@ impl MintBuilder {
         self
     }
 
+    pub fn build_circuit(
+        &self,
+        proof_generation_key: &ProofGenerationKey,
+        public_key_randomness: &ironfish_jubjub::Fr,
+    ) -> MintAsset {
+        MintAsset {
+            proof_generation_key: Some(proof_generation_key.clone()),
+            public_key_randomness: Some(*public_key_randomness),
+        }
+    }
+
     pub fn build(
         &self,
         proof_generation_key: &ProofGenerationKey,
         public_address: &PublicAddress,
         public_key_randomness: &ironfish_jubjub::Fr,
         randomized_public_key: &redjubjub::PublicKey,
     ) -> Result<UnsignedMintDescription, IronfishError> {
-        let circuit = MintAsset {
-            proof_generation_key: Some(proof_generation_key.clone()),
-            public_key_randomness: Some(*public_key_randomness),
-        };
+        let circuit = self.build_circuit(proof_generation_key, public_key_randomness);
 
         let proof = groth16::create_random_proof(circuit, &SAPLING.mint_params, &mut thread_rng())?;
 

ironfish-rust/src/transaction/outputs.rs

@@ -74,6 +74,24 @@ impl OutputBuilder {
         ExtendedPoint::from(self.value_commitment.commitment())
     }
 
+    pub(crate) fn build_circuit(
+        &self,
+        proof_generation_key: &ProofGenerationKey,
+        public_key_randomness: &ironfish_jubjub::Fr,
+    ) -> (Output, EphemeralKeyPair) {
+        let key_pair = EphemeralKeyPair::new();
+        let circuit = Output {
+            value_commitment: Some(self.value_commitment.clone()),
+            payment_address: Some(self.note.owner.0),
+            commitment_randomness: Some(self.note.randomness),
+            esk: Some(*key_pair.secret()),
+            asset_id: *self.note.asset_id().as_bytes(),
+            proof_generation_key: Some(proof_generation_key.clone()),
+            ar: Some(*public_key_randomness),
+        };
+        (circuit, key_pair)
+    }
+
     /// Construct and return the committed [`OutputDescription`] for this receiving calculation.
     ///
     /// The [`OutputDescription`] is the publicly visible form of the new note, not
@@ -88,17 +106,8 @@ impl OutputBuilder {
         public_key_randomness: &ironfish_jubjub::Fr,
         randomized_public_key: &redjubjub::PublicKey,
     ) -> Result<OutputDescription, IronfishError> {
-        let diffie_hellman_keys = EphemeralKeyPair::new();
-
-        let circuit = Output {
-            value_commitment: Some(self.value_commitment.clone()),
-            payment_address: Some(self.note.owner.0),
-            commitment_randomness: Some(self.note.randomness),
-            esk: Some(*diffie_hellman_keys.secret()),
-            asset_id: *self.note.asset_id().as_bytes(),
-            proof_generation_key: Some(proof_generation_key.clone()),
-            ar: Some(*public_key_randomness),
-        };
+        let (circuit, diffie_hellman_keys) =
+            self.build_circuit(proof_generation_key, public_key_randomness);
 
         let proof =
             groth16::create_random_proof(circuit, &SAPLING.output_params, &mut thread_rng())?;

ironfish-rust/src/transaction/proposed.rs

@@ -8,7 +8,7 @@ use crate::{
         asset_identifier::{AssetIdentifier, NATIVE_ASSET},
     },
     errors::{IronfishError, IronfishErrorKind},
-    keys::{PublicAddress, SaplingKey},
+    keys::{EphemeralKeyPair, PublicAddress, SaplingKey},
     note::Note,
     transaction::{
         burns::{BurnBuilder, BurnDescription},
@@ -32,6 +32,7 @@ use group::GroupEncoding;
 use ironfish_jubjub::ExtendedPoint;
 use ironfish_zkp::{
     constants::{SPENDING_KEY_GENERATOR, VALUE_COMMITMENT_RANDOMNESS_GENERATOR},
+    proofs,
     redjubjub::{self, Signature},
     ProofGenerationKey,
 };
@@ -195,6 +196,49 @@ impl ProposedTransaction {
         Ok(())
     }
 
+    #[allow(clippy::type_complexity)]
+    pub fn build_circuits(
+        &mut self,
+        proof_authorizing_key: ironfish_jubjub::Fr,
+        view_key: ViewKey,
+        intended_transaction_fee: i64,
+        change_goes_to: Option<PublicAddress>,
+    ) -> Result<
+        (
+            Vec<proofs::Spend>,
+            Vec<(proofs::Output, EphemeralKeyPair)>,
+            Vec<proofs::MintAsset>,
+        ),
+        IronfishError,
+    > {
+        let public_address = view_key.public_address()?;
+        let proof_generation_key =
+            ProofGenerationKey::new(view_key.authorizing_key, proof_authorizing_key);
+
+        let is_miners_fee = self.outputs.iter().any(|output| output.get_is_miners_fee());
+        if !is_miners_fee {
+            self.add_change_notes(change_goes_to, public_address, intended_transaction_fee)?;
+        }
+
+        let spend_circuits = self
+            .spends
+            .iter()
+            .map(|spend| spend.build_circuit(&proof_generation_key, &self.public_key_randomness))
+            .collect();
+        let output_circuits = self
+            .outputs
+            .iter()
+            .map(|output| output.build_circuit(&proof_generation_key, &self.public_key_randomness))
+            .collect();
+        let mint_circuits = self
+            .mints
+            .iter()
+            .map(|mint| mint.build_circuit(&proof_generation_key, &self.public_key_randomness))
+            .collect();
+
+        Ok((spend_circuits, output_circuits, mint_circuits))
+    }
+
     pub fn build(
         &mut self,
         proof_authorizing_key: ironfish_jubjub::Fr,

ironfish-rust/src/transaction/spends.rs

@@ -68,7 +68,7 @@ impl SpendBuilder {
     /// This is the only time this API thinks about the merkle tree. The witness
     /// contains the root-hash at the time the witness was created and the path
     /// to verify the location of that note in the tree.
-    pub(crate) fn new<W: WitnessTrait + ?Sized>(note: Note, witness: &W) -> Self {
+    pub fn new<W: WitnessTrait + ?Sized>(note: Note, witness: &W) -> Self {
         let value_commitment = ValueCommitment::new(note.value, note.asset_generator());
 
         SpendBuilder {
@@ -89,12 +89,29 @@ impl SpendBuilder {
         ExtendedPoint::from(self.value_commitment.commitment())
     }
 
+    pub fn build_circuit(
+        &self,
+        proof_generation_key: &ProofGenerationKey,
+        public_key_randomness: &Fr,
+    ) -> Spend {
+        Spend {
+            value_commitment: Some(self.value_commitment.clone()),
+            proof_generation_key: Some(proof_generation_key.clone()),
+            payment_address: Some(self.note.owner.0),
+            auth_path: self.auth_path.clone(),
+            commitment_randomness: Some(self.note.randomness),
+            anchor: Some(self.root_hash),
+            ar: Some(*public_key_randomness),
+            sender_address: Some(self.note.sender.0),
+        }
+    }
+
     /// Sign this spend with the private key, and return a [`SpendDescription`]
     /// suitable for serialization.
     ///
     /// Verifies the proof before returning to prevent posting broken
     /// transactions
-    pub(crate) fn build(
+    pub fn build(
         &self,
         proof_generation_key: &ProofGenerationKey,
         view_key: &ViewKey,
@@ -103,16 +120,7 @@ impl SpendBuilder {
     ) -> Result<UnsignedSpendDescription, IronfishError> {
         let value_commitment_point = self.value_commitment_point();
 
-        let circuit = Spend {
-            value_commitment: Some(self.value_commitment.clone()),
-            proof_generation_key: Some(proof_generation_key.clone()),
-            payment_address: Some(self.note.owner.0),
-            auth_path: self.auth_path.clone(),
-            commitment_randomness: Some(self.note.randomness),
-            anchor: Some(self.root_hash),
-            ar: Some(*public_key_randomness),
-            sender_address: Some(self.note.sender.0),
-        };
+        let circuit = self.build_circuit(proof_generation_key, public_key_randomness);
 
         // Proof that the spend was valid and successful for the provided owner
         // and note.