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hashchain.rs
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hashchain.rs
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//! This example proves the knowledge of preimage to a hash chain tail, with a configurable number of elements per hash chain node.
//! The output of each step tracks the current tail of the hash chain
use bellpepper_core::{num::AllocatedNum, ConstraintSystem, SynthesisError};
use ff::Field;
use flate2::{write::ZlibEncoder, Compression};
use generic_array::typenum::U24;
use neptune::{
circuit2::Elt,
sponge::{
api::{IOPattern, SpongeAPI, SpongeOp},
circuit::SpongeCircuit,
vanilla::{Mode::Simplex, Sponge, SpongeTrait},
},
Strength,
};
use nova_snark::{
provider::{Bn256EngineKZG, GrumpkinEngine},
traits::{
circuit::{StepCircuit, TrivialCircuit},
snark::RelaxedR1CSSNARKTrait,
Engine, Group,
},
CompressedSNARK, PublicParams, RecursiveSNARK,
};
use std::time::Instant;
type E1 = Bn256EngineKZG;
type E2 = GrumpkinEngine;
type EE1 = nova_snark::provider::hyperkzg::EvaluationEngine<E1>;
type EE2 = nova_snark::provider::ipa_pc::EvaluationEngine<E2>;
type S1 = nova_snark::spartan::snark::RelaxedR1CSSNARK<E1, EE1>; // non-preprocessing SNARK
type S2 = nova_snark::spartan::snark::RelaxedR1CSSNARK<E2, EE2>; // non-preprocessing SNARK
#[derive(Clone, Debug)]
struct HashChainCircuit<G: Group> {
num_elts_per_step: usize,
x_i: Vec<G::Scalar>,
}
impl<G: Group> HashChainCircuit<G> {
// produces a preimage to be hashed
fn new(num_elts_per_step: usize) -> Self {
let mut rng = rand::thread_rng();
let x_i = (0..num_elts_per_step)
.map(|_| G::Scalar::random(&mut rng))
.collect::<Vec<_>>();
Self {
num_elts_per_step,
x_i,
}
}
}
impl<G: Group> StepCircuit<G::Scalar> for HashChainCircuit<G> {
fn arity(&self) -> usize {
1
}
fn synthesize<CS: ConstraintSystem<G::Scalar>>(
&self,
cs: &mut CS,
z_in: &[AllocatedNum<G::Scalar>],
) -> Result<Vec<AllocatedNum<G::Scalar>>, SynthesisError> {
// z_in provides the running digest
assert_eq!(z_in.len(), 1);
// allocate x_i
let x_i = (0..self.num_elts_per_step)
.map(|i| AllocatedNum::alloc(cs.namespace(|| format!("x_{}", i)), || Ok(self.x_i[i])))
.collect::<Result<Vec<_>, _>>()?;
// concatenate z_in and x_i
let mut m = z_in.to_vec();
m.extend(x_i);
let elt = m
.iter()
.map(|x| Elt::Allocated(x.clone()))
.collect::<Vec<_>>();
let num_absorbs = 1 + self.num_elts_per_step as u32;
let parameter = IOPattern(vec![SpongeOp::Absorb(num_absorbs), SpongeOp::Squeeze(1u32)]);
let pc = Sponge::<G::Scalar, U24>::api_constants(Strength::Standard);
let mut ns = cs.namespace(|| "ns");
let z_out = {
let mut sponge = SpongeCircuit::new_with_constants(&pc, Simplex);
let acc = &mut ns;
sponge.start(parameter, None, acc);
neptune::sponge::api::SpongeAPI::absorb(&mut sponge, num_absorbs, &elt, acc);
let output = neptune::sponge::api::SpongeAPI::squeeze(&mut sponge, 1, acc);
sponge.finish(acc).unwrap();
Elt::ensure_allocated(&output[0], &mut ns.namespace(|| "ensure allocated"), true)?
};
Ok(vec![z_out])
}
}
/// cargo run --release --example and
fn main() {
println!("=========================================================");
println!("Nova-based hashchain example");
println!("=========================================================");
let num_steps = 10;
for num_elts_per_step in [1024, 2048, 4096] {
// number of instances of AND per Nova's recursive step
let circuit_primary = HashChainCircuit::new(num_elts_per_step);
let circuit_secondary = TrivialCircuit::default();
// produce public parameters
let start = Instant::now();
println!("Producing public parameters...");
let pp = PublicParams::<
E1,
E2,
HashChainCircuit<<E1 as Engine>::GE>,
TrivialCircuit<<E2 as Engine>::Scalar>,
>::setup(
&circuit_primary,
&circuit_secondary,
&*S1::ck_floor(),
&*S2::ck_floor(),
)
.unwrap();
println!("PublicParams::setup, took {:?} ", start.elapsed());
println!(
"Number of constraints per step (primary circuit): {}",
pp.num_constraints().0
);
println!(
"Number of constraints per step (secondary circuit): {}",
pp.num_constraints().1
);
println!(
"Number of variables per step (primary circuit): {}",
pp.num_variables().0
);
println!(
"Number of variables per step (secondary circuit): {}",
pp.num_variables().1
);
// produce non-deterministic advice
let circuits = (0..num_steps)
.map(|_| HashChainCircuit::new(num_elts_per_step))
.collect::<Vec<_>>();
type C1 = HashChainCircuit<<E1 as Engine>::GE>;
type C2 = TrivialCircuit<<E2 as Engine>::Scalar>;
// produce a recursive SNARK
println!(
"Generating a RecursiveSNARK with {num_elts_per_step} field elements per hashchain node..."
);
let mut recursive_snark: RecursiveSNARK<E1, E2, C1, C2> =
RecursiveSNARK::<E1, E2, C1, C2>::new(
&pp,
&circuits[0],
&circuit_secondary,
&[<E1 as Engine>::Scalar::zero()],
&[<E2 as Engine>::Scalar::zero()],
)
.unwrap();
for (i, circuit_primary) in circuits.iter().enumerate() {
let start = Instant::now();
let res = recursive_snark.prove_step(&pp, circuit_primary, &circuit_secondary);
assert!(res.is_ok());
println!("RecursiveSNARK::prove {} : took {:?} ", i, start.elapsed());
}
// verify the recursive SNARK
println!("Verifying a RecursiveSNARK...");
let res = recursive_snark.verify(
&pp,
num_steps,
&[<E1 as Engine>::Scalar::ZERO],
&[<E2 as Engine>::Scalar::ZERO],
);
println!("RecursiveSNARK::verify: {:?}", res.is_ok(),);
assert!(res.is_ok());
// produce a compressed SNARK
println!("Generating a CompressedSNARK using Spartan with HyperKZG...");
let (pk, vk) = CompressedSNARK::<_, _, _, _, S1, S2>::setup(&pp).unwrap();
let start = Instant::now();
let res = CompressedSNARK::<_, _, _, _, S1, S2>::prove(&pp, &pk, &recursive_snark);
println!(
"CompressedSNARK::prove: {:?}, took {:?}",
res.is_ok(),
start.elapsed()
);
assert!(res.is_ok());
let compressed_snark = res.unwrap();
let mut encoder = ZlibEncoder::new(Vec::new(), Compression::default());
bincode::serialize_into(&mut encoder, &compressed_snark).unwrap();
let compressed_snark_encoded = encoder.finish().unwrap();
println!(
"CompressedSNARK::len {:?} bytes",
compressed_snark_encoded.len()
);
// verify the compressed SNARK
println!("Verifying a CompressedSNARK...");
let start = Instant::now();
let res = compressed_snark.verify(
&vk,
num_steps,
&[<E1 as Engine>::Scalar::ZERO],
&[<E2 as Engine>::Scalar::ZERO],
);
println!(
"CompressedSNARK::verify: {:?}, took {:?}",
res.is_ok(),
start.elapsed()
);
assert!(res.is_ok());
println!("=========================================================");
}
}