Introduce input multipacking abstraction for nullifiers.
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@ -9,6 +9,7 @@ pub mod num;
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pub mod lookup;
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pub mod ecc;
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pub mod pedersen_hash;
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pub mod multipack;
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use pairing::{
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PrimeField,
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@ -0,0 +1,106 @@
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use pairing::{Engine, Field, PrimeField};
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use bellman::{ConstraintSystem, SynthesisError};
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use super::boolean::{Boolean};
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use super::num::Num;
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use super::Assignment;
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/// Takes a sequence of booleans and exposes them as compact
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/// public inputs
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pub fn pack_into_inputs<E, CS>(
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mut cs: CS,
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bits: &[Boolean]
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) -> Result<(), SynthesisError>
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where E: Engine, CS: ConstraintSystem<E>
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{
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for (i, bits) in bits.chunks(E::Fr::CAPACITY as usize).enumerate()
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{
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let mut num = Num::<E>::zero();
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let mut coeff = E::Fr::one();
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for bit in bits {
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num = num.add_bool_with_coeff(CS::one(), bit, coeff);
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coeff.double();
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}
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let input = cs.alloc_input(|| format!("input {}", i), || {
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Ok(*num.get_value().get()?)
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})?;
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// num * 1 = input
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cs.enforce(
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|| format!("packing constraint {}", i),
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|_| num.lc(E::Fr::one()),
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|lc| lc + CS::one(),
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|lc| lc + input
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);
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}
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Ok(())
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}
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pub fn bytes_to_bits(bytes: &[u8]) -> Vec<bool>
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{
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bytes.iter()
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.flat_map(|&v| (0..8).rev().map(move |i| (v >> i) & 1 == 1))
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.collect()
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}
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pub fn compute_multipacking<E: Engine>(
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bits: &[bool]
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) -> Vec<E::Fr>
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{
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let mut result = vec![];
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for bits in bits.chunks(E::Fr::CAPACITY as usize)
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{
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let mut cur = E::Fr::zero();
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let mut coeff = E::Fr::one();
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for bit in bits {
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if *bit {
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cur.add_assign(&coeff);
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}
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coeff.double();
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}
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result.push(cur);
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}
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result
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}
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#[test]
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fn test_multipacking() {
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use rand::{SeedableRng, Rng, XorShiftRng};
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use bellman::{ConstraintSystem};
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use pairing::bls12_381::{Bls12};
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use ::circuit::test::*;
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use super::boolean::{AllocatedBit, Boolean};
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let mut rng = XorShiftRng::from_seed([0x3dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
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for num_bits in 0..1500 {
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let mut cs = TestConstraintSystem::<Bls12>::new();
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let bits: Vec<bool> = (0..num_bits).map(|_| rng.gen()).collect();
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let circuit_bits = bits.iter().enumerate()
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.map(|(i, &b)| {
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Boolean::from(
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AllocatedBit::alloc(
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cs.namespace(|| format!("bit {}", i)),
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Some(b)
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).unwrap()
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)
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})
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.collect::<Vec<_>>();
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let expected_inputs = compute_multipacking::<Bls12>(&bits);
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pack_into_inputs(cs.namespace(|| "pack"), &circuit_bits).unwrap();
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assert!(cs.is_satisfied());
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assert!(cs.verify(&expected_inputs));
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}
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}
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