port sha256 bench from nova

Cargo.toml

@@ -50,6 +50,10 @@ cfg-if = "1.0.0"
 sha2 = "0.10.7"
 proptest = "1.2.0"
 
+[[bench]]
+name = "sha256"
+harness = false
+
 [features]
 default = []
 # Compiles in portable mode, w/o ISA extensions => binary can be executed on all systems.

benches/sha256.rs

@@ -0,0 +1,153 @@
+//! Benchmarks Spartan's prover for proving SHA-256 with varying sized messages.
+//! This code invokes a hand-written SHA-256 gadget from bellman/bellperson.
+//! It also uses code from bellman/bellperson to compare circuit-generated digest with sha2 crate's output
+#![allow(non_snake_case)]
+use bellperson::gadgets::{sha256::sha256, Assignment};
+use bellperson::{gadgets::{
+  boolean::{AllocatedBit, Boolean},
+  num::{AllocatedNum, Num}},
+  Circuit,ConstraintSystem, SynthesisError,
+};
+use core::time::Duration;
+use criterion::*;
+use ff::{PrimeField, PrimeFieldBits};
+use spartan2::{traits::Group,SNARK};
+use sha2::{Digest, Sha256};
+use std::marker::PhantomData;
+
+type G = pasta_curves::pallas::Point;
+type EE = spartan2::provider::hyrax_pc::HyraxEvaluationEngine<G>;
+type S = spartan2::spartan::snark::RelaxedR1CSSNARK<G, EE>;
+
+#[derive(Clone, Debug)]
+struct Sha256Circuit<Scalar: PrimeField> {
+  preimage: Vec<u8>,
+  _p: PhantomData<Scalar>,
+}
+
+impl<Scalar: PrimeField + PrimeFieldBits> Sha256Circuit<Scalar> {
+  pub fn new(preimage: Vec<u8>) -> Self {
+    Self {
+      preimage,
+      _p: PhantomData,
+    }
+  }
+}
+
+impl<Scalar: PrimeField> Circuit<Scalar> for Sha256Circuit<Scalar> {
+  fn synthesize<CS: ConstraintSystem<Scalar>>(
+    self, 
+    cs: &mut CS,
+  ) -> Result<(), SynthesisError> {
+    let bit_values: Vec<_> = self
+      .preimage
+      .clone()
+      .into_iter()
+      .flat_map(|byte| (0..8).map(move |i| (byte >> i) & 1u8 == 1u8))
+      .map(Some)
+      .collect();
+    assert_eq!(bit_values.len(), self.preimage.len() * 8);
+
+    let preimage_bits = bit_values
+      .into_iter()
+      .enumerate()
+      .map(|(i, b)| AllocatedBit::alloc(cs.namespace(|| format!("preimage bit {i}")), b))
+      .map(|b| b.map(Boolean::from))
+      .collect::<Result<Vec<_>, _>>()?;
+
+    let hash_bits = sha256(cs.namespace(|| "sha256"), &preimage_bits)?;
+
+    for (i, hash_bits) in hash_bits.chunks(256_usize).enumerate() {
+      let mut num = Num::<Scalar>::zero();
+      let mut coeff = Scalar::ONE;
+      for bit in hash_bits {
+        num = num.add_bool_with_coeff(CS::one(), bit, coeff);
+
+        coeff = coeff.double();
+      }
+
+      let hash = AllocatedNum::alloc(cs.namespace(|| format!("input {i}")), || {
+        Ok(*num.get_value().get()?)
+      })?;
+
+      // num * 1 = hash
+      cs.enforce(
+        || format!("packing constraint {i}"),
+        |_| num.lc(Scalar::ONE),
+        |lc| lc + CS::one(),
+        |lc| lc + hash.get_variable(),
+      );
+    }
+
+    // sanity check with the hasher
+    let mut hasher = Sha256::new();
+    hasher.update(&self.preimage);
+    let hash_result = hasher.finalize();
+
+    let mut s = hash_result
+      .iter()
+      .flat_map(|&byte| (0..8).rev().map(move |i| (byte >> i) & 1u8 == 1u8));
+
+    for b in hash_bits {
+      match b {
+        Boolean::Is(b) => {
+          assert!(s.next().unwrap() == b.get_value().unwrap());
+        }
+        Boolean::Not(b) => {
+          assert!(s.next().unwrap() != b.get_value().unwrap());
+        }
+        Boolean::Constant(_b) => {
+          panic!("Can't reach here")
+        }
+      }
+    }
+    Ok(())
+  }
+}
+
+criterion_group! {
+name = snark;
+config = Criterion::default().warm_up_time(Duration::from_millis(3000));
+targets = bench_snark
+}
+
+criterion_main!(snark);
+
+fn bench_snark(c: &mut Criterion) {
+  // Test vectors
+  let circuits = vec![
+    Sha256Circuit::new(vec![0u8; 1 << 6]),
+    Sha256Circuit::new(vec![0u8; 1 << 7]),
+    Sha256Circuit::new(vec![0u8; 1 << 8]),
+    Sha256Circuit::new(vec![0u8; 1 << 9]),
+    Sha256Circuit::new(vec![0u8; 1 << 10]),
+    Sha256Circuit::new(vec![0u8; 1 << 11]),
+    Sha256Circuit::new(vec![0u8; 1 << 12]),
+    Sha256Circuit::new(vec![0u8; 1 << 13]),
+    Sha256Circuit::new(vec![0u8; 1 << 14]),
+    Sha256Circuit::new(vec![0u8; 1 << 15]),
+    Sha256Circuit::new(vec![0u8; 1 << 16]),
+  ];
+
+  for circuit in circuits {
+    let mut group = c.benchmark_group(format!(
+      "SpartanProve-Sha256-message-len-{}",
+      circuit.preimage.len()
+    ));
+    group.sample_size(10);
+
+    // produce keys
+    let (pk, _vk) =
+      SNARK::<G, S, Sha256Circuit<<G as Group>::Scalar>>::setup(circuit.clone()).unwrap();
+
+    group.bench_function("Prove", |b| {
+      let res = b.iter(|| {
+        SNARK::<G, S, Sha256Circuit<<G as Group>::Scalar>>::prove(
+          black_box(&pk),
+          black_box(circuit.clone()),
+        );
+      });
+    });
+    group.finish();
+  }
+}