New implementation of library API.

Cargo.toml

@@ -13,7 +13,7 @@ rand = "0.3"
 bit-vec = "0.4.4"
 futures = "0.1"
 futures-cpupool = "0.1"
-num_cpus = "1.6"
+num_cpus = "1"
 crossbeam = "0.3"
 pairing = "0.13"
 

examples/mimc.rs

@@ -0,0 +1,239 @@
+extern crate bellman;
+extern crate pairing;
+extern crate rand;
+
+// For randomness (during paramgen and proof generation)
+use rand::{thread_rng, Rng};
+
+// For benchmarking
+use std::time::{Duration, Instant};
+
+// Bring in some tools for using pairing-friendly curves
+use pairing::{
+    Engine,
+    Field
+};
+
+// We're going to use the BLS12-381 pairing-friendly elliptic curve.
+use pairing::bls12_381::{
+    Bls12
+};
+
+// We'll use these interfaces to construct our circuit.
+use bellman::{
+    Circuit,
+    ConstraintSystem,
+    SynthesisError
+};
+
+// We're going to use the Groth16 proving system.
+use bellman::groth16::{
+    generate_random_parameters,
+    prepare_verifying_key,
+    create_random_proof,
+    verify_proof,
+};
+
+const MIMC_ROUNDS: usize = 322;
+
+/// This is an implementation of MiMC, specifically a
+/// variant named `LongsightF322p3` for BLS12-381.
+/// See http://eprint.iacr.org/2016/492 for more 
+/// information about this construction.
+///
+/// ```
+/// function LongsightF322p3(xL ⦂ Fp, xR ⦂ Fp) {
+///     for i from 0 up to 321 {
+///         xL, xR := xR + (xL + Ci)^3, xL
+///     }
+///     return xL
+/// }
+/// ```
+fn mimc<E: Engine>(
+    mut xl: E::Fr,
+    mut xr: E::Fr,
+    constants: &[E::Fr]
+) -> E::Fr
+{
+    assert_eq!(constants.len(), MIMC_ROUNDS);
+
+    for i in 0..MIMC_ROUNDS {
+        let mut tmp1 = xl;
+        tmp1.add_assign(&constants[i]);
+        let mut tmp2 = tmp1;
+        tmp2.square();
+        tmp2.mul_assign(&tmp1);
+        tmp2.add_assign(&xr);
+        xr = xl;
+        xl = tmp2;
+    }
+
+    xl
+}
+
+/// This is our demo circuit for proving knowledge of the
+/// preimage of a MiMC hash invocation.
+struct MiMCDemo<'a, E: Engine> {
+    xl: Option<E::Fr>,
+    xr: Option<E::Fr>,
+    constants: &'a [E::Fr]
+}
+
+/// Our demo circuit implements this `Circuit` trait which
+/// is used during paramgen and proving in order to
+/// synthesize the constraint system.
+impl<'a, E: Engine> Circuit<E> for MiMCDemo<'a, E> {
+    fn synthesize<CS: ConstraintSystem<E>>(
+        self,
+        cs: &mut CS
+    ) -> Result<(), SynthesisError>
+    {
+        assert_eq!(self.constants.len(), MIMC_ROUNDS);
+
+        // Allocate the first component of the preimage.
+        let mut xl_value = self.xl;
+        let mut xl = cs.alloc(|| "preimage xl", || {
+            xl_value.ok_or(SynthesisError::AssignmentMissing)
+        })?;
+
+        // Allocate the second component of the preimage.
+        let mut xr_value = self.xr;
+        let mut xr = cs.alloc(|| "preimage xr", || {
+            xr_value.ok_or(SynthesisError::AssignmentMissing)
+        })?;
+
+        for i in 0..MIMC_ROUNDS {
+            // xL, xR := xR + (xL + Ci)^3, xL
+            let cs = &mut cs.namespace(|| format!("round {}", i));
+
+            // tmp = (xL + Ci)^2
+            let mut tmp_value = xl_value.map(|mut e| {
+                e.add_assign(&self.constants[i]);
+                e.square();
+                e
+            });
+            let mut tmp = cs.alloc(|| "tmp", || {
+                tmp_value.ok_or(SynthesisError::AssignmentMissing)
+            })?;
+
+            cs.enforce(
+                || "tmp = (xL + Ci)^2",
+                |lc| lc + xl + (self.constants[i], CS::one()),
+                |lc| lc + xl + (self.constants[i], CS::one()),
+                |lc| lc + tmp
+            );
+
+            // new_xL = xR + (xL + Ci)^3
+            // new_xL = xR + tmp * (xL + Ci)
+            // new_xL - xR = tmp * (xL + Ci)
+            let mut new_xl_value = xl_value.map(|mut e| {
+                e.add_assign(&self.constants[i]);
+                e.mul_assign(&tmp_value.unwrap());
+                e.add_assign(&xr_value.unwrap());
+                e
+            });
+
+            let mut new_xl = if i == (MIMC_ROUNDS-1) {
+                // This is the last round, xL is our image and so
+                // we allocate a public input.
+                cs.alloc_input(|| "image", || {
+                    new_xl_value.ok_or(SynthesisError::AssignmentMissing)
+                })?
+            } else {
+                cs.alloc(|| "new_xl", || {
+                    new_xl_value.ok_or(SynthesisError::AssignmentMissing)
+                })?
+            };
+
+            cs.enforce(
+                || "new_xL = xR + (xL + Ci)^3",
+                |lc| lc + tmp,
+                |lc| lc + xl + (self.constants[i], CS::one()),
+                |lc| lc + new_xl - xr
+            );
+
+            // xR = xL
+            xr = xl;
+            xr_value = xl_value;
+
+            // xL = new_xL
+            xl = new_xl;
+            xl_value = new_xl_value;
+        }
+
+        Ok(())
+    }
+}
+
+fn main() {
+    // This may not be cryptographically safe, use
+    // `OsRng` (for example) in production software.
+    let rng = &mut thread_rng();
+
+    // Generate the MiMC round constants
+    let constants = (0..MIMC_ROUNDS).map(|_| rng.gen()).collect::<Vec<_>>();
+
+    println!("Creating parameters...");
+
+    // Create parameters for our circuit
+    let params = {
+        let c = MiMCDemo::<Bls12> {
+            xl: None,
+            xr: None,
+            constants: &constants
+        };
+
+        generate_random_parameters(c, rng).unwrap()
+    };
+
+    // Prepare the verification key (for proof verification)
+    let pvk = prepare_verifying_key(&params.vk);
+
+    println!("Creating proofs...");
+
+    // Let's benchmark stuff!
+    const SAMPLES: u32 = 50;
+    let mut total_proving = Duration::new(0, 0);
+    let mut total_verifying = Duration::new(0, 0);
+
+    for _ in 0..SAMPLES {
+        // Generate a random preimage and compute the image
+        let xl = rng.gen();
+        let xr = rng.gen();
+        let image = mimc::<Bls12>(xl, xr, &constants);
+
+        let start = Instant::now();
+        let proof = {
+            // Create an instance of our circuit (with the
+            // witness)
+            let c = MiMCDemo {
+                xl: Some(xl),
+                xr: Some(xr),
+                constants: &constants
+            };
+
+            // Create a groth16 proof with our parameters.
+            create_random_proof(c, &params, rng).unwrap()
+        };
+        total_proving += start.elapsed();
+
+        let start = Instant::now();
+        // Check the proof
+        assert!(verify_proof(
+            &pvk,
+            &proof,
+            &[image]
+        ).unwrap());
+        total_verifying += start.elapsed();
+    }
+    let proving_avg = total_proving / SAMPLES;
+    let proving_avg = proving_avg.subsec_nanos() as f64 / 1_000_000_000f64
+                      + (proving_avg.as_secs() as f64);
+
+    let verifying_avg = total_verifying / SAMPLES;
+    let verifying_avg = verifying_avg.subsec_nanos() as f64 / 1_000_000_000f64
+                      + (verifying_avg.as_secs() as f64);
+
+    println!("Average proving time: {:?} seconds", proving_avg);
+    println!("Average verifying time: {:?} seconds", verifying_avg);
+}