Merge pull request #79 from ebfull/pedersen-hash-performance
Improve Pedersen hash performance
This commit is contained in:
commit
b70d6e66fc
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@ -0,0 +1,23 @@
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#![feature(test)]
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extern crate rand;
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extern crate test;
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extern crate pairing;
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extern crate sapling_crypto;
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use rand::{Rand, thread_rng};
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use pairing::bls12_381::Bls12;
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use sapling_crypto::jubjub::JubjubBls12;
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use sapling_crypto::pedersen_hash::{pedersen_hash, Personalization};
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#[bench]
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fn bench_pedersen_hash(b: &mut test::Bencher) {
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let params = JubjubBls12::new();
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let rng = &mut thread_rng();
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let bits = (0..510).map(|_| bool::rand(rng)).collect::<Vec<_>>();
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let personalization = Personalization::MerkleTree(31);
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b.iter(|| {
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pedersen_hash::<Bls12, _>(personalization, bits.clone(), ¶ms)
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});
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}
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@ -355,12 +355,72 @@ impl<E: JubjubEngine, Subgroup> Point<E, Subgroup> {
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p
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}
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pub fn double(&self, params: &E::Params) -> Self {
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// Point addition is unified and complete.
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// There are dedicated formulae, but we do
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// not implement these now.
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pub fn double(&self, _: &E::Params) -> Self {
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// See "Twisted Edwards Curves Revisited"
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// Huseyin Hisil, Kenneth Koon-Ho Wong, Gary Carter, and Ed Dawson
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// Section 3.3
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// http://hyperelliptic.org/EFD/g1p/auto-twisted-extended.html#doubling-dbl-2008-hwcd
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self.add(self, params)
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// A = X1^2
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let mut a = self.x;
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a.square();
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// B = Y1^2
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let mut b = self.y;
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b.square();
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// C = 2*Z1^2
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let mut c = self.z;
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c.square();
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c.double();
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// D = a*A
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// = -A
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let mut d = a;
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d.negate();
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// E = (X1+Y1)^2 - A - B
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let mut e = self.x;
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e.add_assign(&self.y);
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e.square();
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e.add_assign(&d); // -A = D
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e.sub_assign(&b);
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// G = D+B
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let mut g = d;
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g.add_assign(&b);
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// F = G-C
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let mut f = g;
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f.sub_assign(&c);
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// H = D-B
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let mut h = d;
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h.sub_assign(&b);
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// X3 = E*F
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let mut x3 = e;
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x3.mul_assign(&f);
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// Y3 = G*H
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let mut y3 = g;
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y3.mul_assign(&h);
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// T3 = E*H
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let mut t3 = e;
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t3.mul_assign(&h);
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// Z3 = F*G
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let mut z3 = f;
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z3.mul_assign(&g);
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Point {
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x: x3,
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y: y3,
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t: t3,
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z: z3,
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_marker: PhantomData
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}
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}
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pub fn add(&self, other: &Self, params: &E::Params) -> Self
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@ -112,6 +112,8 @@ pub trait JubjubParams<E: JubjubEngine>: Sized {
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fn scale(&self) -> &E::Fr;
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/// Returns the generators (for each segment) used in all Pedersen commitments.
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fn pedersen_hash_generators(&self) -> &[edwards::Point<E, PrimeOrder>];
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/// Returns the exp table for Pedersen hashes.
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fn pedersen_hash_exp_table(&self) -> &[Vec<Vec<edwards::Point<E, PrimeOrder>>>];
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/// Returns the maximum number of chunks per segment of the Pedersen hash.
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fn pedersen_hash_chunks_per_generator(&self) -> usize;
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/// Returns the pre-computed window tables [-4, 3, 2, 1, 1, 2, 3, 4] of different
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@ -126,6 +128,9 @@ pub trait JubjubParams<E: JubjubEngine>: Sized {
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/// Returns a window table [0, 1, ..., 8] for different magnitudes of some
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/// fixed generator.
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fn circuit_generators(&self, FixedGenerators) -> &[Vec<(E::Fr, E::Fr)>];
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/// Returns the window size for exponentiation of Pedersen hash generators
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/// outside the circuit
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fn pedersen_hash_exp_window_size() -> u32;
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}
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impl JubjubEngine for Bls12 {
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@ -140,6 +145,7 @@ pub struct JubjubBls12 {
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scale: Fr,
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pedersen_hash_generators: Vec<edwards::Point<Bls12, PrimeOrder>>,
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pedersen_hash_exp: Vec<Vec<Vec<edwards::Point<Bls12, PrimeOrder>>>>,
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pedersen_circuit_generators: Vec<Vec<Vec<(Fr, Fr)>>>,
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fixed_base_generators: Vec<edwards::Point<Bls12, PrimeOrder>>,
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@ -154,6 +160,9 @@ impl JubjubParams<Bls12> for JubjubBls12 {
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fn pedersen_hash_generators(&self) -> &[edwards::Point<Bls12, PrimeOrder>] {
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&self.pedersen_hash_generators
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}
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fn pedersen_hash_exp_table(&self) -> &[Vec<Vec<edwards::Point<Bls12, PrimeOrder>>>] {
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&self.pedersen_hash_exp
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}
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fn pedersen_hash_chunks_per_generator(&self) -> usize {
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63
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}
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@ -171,6 +180,9 @@ impl JubjubParams<Bls12> for JubjubBls12 {
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{
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&self.fixed_base_circuit_generators[base as usize][..]
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}
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fn pedersen_hash_exp_window_size() -> u32 {
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8
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}
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}
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impl JubjubBls12 {
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@ -191,6 +203,7 @@ impl JubjubBls12 {
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// We'll initialize these below
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pedersen_hash_generators: vec![],
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pedersen_hash_exp: vec![],
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pedersen_circuit_generators: vec![],
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fixed_base_generators: vec![],
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fixed_base_circuit_generators: vec![],
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@ -258,6 +271,42 @@ impl JubjubBls12 {
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tmp_params.pedersen_hash_generators = pedersen_hash_generators;
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}
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// Create the exp table for the Pedersen hash generators
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{
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let mut pedersen_hash_exp = vec![];
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for g in &tmp_params.pedersen_hash_generators {
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let mut g = g.clone();
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let window = JubjubBls12::pedersen_hash_exp_window_size();
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let mut tables = vec![];
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let mut num_bits = 0;
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while num_bits <= fs::Fs::NUM_BITS {
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let mut table = Vec::with_capacity(1 << window);
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let mut base = edwards::Point::zero();
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for _ in 0..(1 << window) {
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table.push(base.clone());
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base = base.add(&g, &tmp_params);
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}
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tables.push(table);
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num_bits += window;
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for _ in 0..window {
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g = g.double(&tmp_params);
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}
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}
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pedersen_hash_exp.push(tables);
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}
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tmp_params.pedersen_hash_exp = pedersen_hash_exp;
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}
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// Create the bases for other parts of the protocol
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{
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let mut fixed_base_generators = vec![edwards::Point::zero(); FixedGenerators::Max as usize];
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@ -1,6 +1,7 @@
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use jubjub::*;
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use pairing::*;
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#[derive(Copy, Clone)]
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pub enum Personalization {
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NoteCommitment,
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MerkleTree(usize)
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@ -31,7 +32,7 @@ pub fn pedersen_hash<E, I>(
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let mut bits = personalization.get_bits().into_iter().chain(bits.into_iter());
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let mut result = edwards::Point::zero();
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let mut generators = params.pedersen_hash_generators().iter();
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let mut generators = params.pedersen_hash_exp_table().iter();
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loop {
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let mut acc = E::Fs::zero();
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@ -78,8 +79,23 @@ pub fn pedersen_hash<E, I>(
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break;
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}
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let mut tmp = generators.next().expect("we don't have enough generators").clone();
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tmp = tmp.mul(acc, params);
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let mut table: &[Vec<edwards::Point<E, _>>] = &generators.next().expect("we don't have enough generators");
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let window = JubjubBls12::pedersen_hash_exp_window_size();
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let window_mask = (1 << window) - 1;
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let mut acc = acc.into_repr();
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let mut tmp = edwards::Point::zero();
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while !acc.is_zero() {
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let i = (acc.as_ref()[0] & window_mask) as usize;
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tmp = tmp.add(&table[0][i], params);
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acc.shr(window);
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table = &table[1..];
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}
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result = result.add(&tmp, params);
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}
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