Expose verifier key's digest with a trait (#243)

* Expose verifier key's digest with a trait * run cargo fmt and clippy
microsoft · Oct 30, 2023 · 02009c2 · 02009c2
1 parent abd43bd
commit 02009c2
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Showing 4 changed files with 29 additions and 7 deletions.
diff --git a/src/spartan/direct.rs b/src/spartan/direct.rs
@@ -9,7 +9,11 @@ use crate::{
   },
   errors::NovaError,
   r1cs::{R1CSShape, RelaxedR1CSInstance, RelaxedR1CSWitness},
-  traits::{circuit::StepCircuit, snark::RelaxedR1CSSNARKTrait, Group},
+  traits::{
+    circuit::StepCircuit,
+    snark::{DigestHelperTrait, RelaxedR1CSSNARKTrait},
+    Group,
+  },
   Commitment, CommitmentKey,
 };
 use bellpepper_core::{num::AllocatedNum, Circuit, ConstraintSystem, SynthesisError};
@@ -75,6 +79,13 @@ where
   vk: S::VerifierKey,
 }
 
+impl<G: Group, S: RelaxedR1CSSNARKTrait<G>> VerifierKey<G, S> {
+  /// Returns the digest of the verifier's key
+  pub fn digest(&self) -> G::Scalar {
+    self.vk.digest()
+  }
+}
+
 /// A direct SNARK proving a step circuit
 #[derive(Clone, Serialize, Deserialize)]
 #[serde(bound = "")]

diff --git a/src/spartan/ppsnark.rs b/src/spartan/ppsnark.rs
@@ -20,7 +20,7 @@ use crate::{
   traits::{
     commitment::{CommitmentEngineTrait, CommitmentTrait},
     evaluation::EvaluationEngineTrait,
-    snark::RelaxedR1CSSNARKTrait,
+    snark::{DigestHelperTrait, RelaxedR1CSSNARKTrait},
     Group, TranscriptEngineTrait, TranscriptReprTrait,
   },
   Commitment, CommitmentKey, CompressedCommitment,
@@ -856,9 +856,10 @@ impl<G: Group, EE: EvaluationEngineTrait<G>> VerifierKey<G, EE> {
       digest: Default::default(),
     }
   }
-
+}
+impl<G: Group, EE: EvaluationEngineTrait<G>> DigestHelperTrait<G> for VerifierKey<G, EE> {
   /// Returns the digest of the verifier's key
-  pub fn digest(&self) -> G::Scalar {
+  fn digest(&self) -> G::Scalar {
     self
       .digest
       .get_or_try_init(|| {

diff --git a/src/spartan/snark.rs b/src/spartan/snark.rs
@@ -15,7 +15,9 @@ use crate::{
     PolyEvalInstance, PolyEvalWitness,
   },
   traits::{
-    evaluation::EvaluationEngineTrait, snark::RelaxedR1CSSNARKTrait, Group, TranscriptEngineTrait,
+    evaluation::EvaluationEngineTrait,
+    snark::{DigestHelperTrait, RelaxedR1CSSNARKTrait},
+    Group, TranscriptEngineTrait,
   },
   Commitment, CommitmentKey,
 };
@@ -53,9 +55,11 @@ impl<G: Group, EE: EvaluationEngineTrait<G>> VerifierKey<G, EE> {
       digest: OnceCell::new(),
     }
   }
+}
 
+impl<G: Group, EE: EvaluationEngineTrait<G>> DigestHelperTrait<G> for VerifierKey<G, EE> {
   /// Returns the digest of the verifier's key.
-  pub fn digest(&self) -> G::Scalar {
+  fn digest(&self) -> G::Scalar {
     self
       .digest
       .get_or_try_init(|| {

diff --git a/src/traits/snark.rs b/src/traits/snark.rs
@@ -16,7 +16,7 @@ pub trait RelaxedR1CSSNARKTrait<G: Group>:
   type ProverKey: Send + Sync + Serialize + for<'de> Deserialize<'de>;
 
   /// A type that represents the verifier's key
-  type VerifierKey: Send + Sync + Serialize + for<'de> Deserialize<'de>;
+  type VerifierKey: Send + Sync + Serialize + for<'de> Deserialize<'de> + DigestHelperTrait<G>;
 
   /// Produces the keys for the prover and the verifier
   fn setup(
@@ -36,3 +36,9 @@ pub trait RelaxedR1CSSNARKTrait<G: Group>:
   /// Verifies a SNARK for a relaxed R1CS
   fn verify(&self, vk: &Self::VerifierKey, U: &RelaxedR1CSInstance<G>) -> Result<(), NovaError>;
 }
+
+/// A helper trait that defines the behavior of a verifier key of `zkSNARK`
+pub trait DigestHelperTrait<G: Group> {
+  /// Returns the digest of the verifier's key
+  fn digest(&self) -> G::Scalar;
+}