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3.7.5 Further document multiexp functions

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This commit is contained in:
Luke Parker
2023-03-02 05:49:39 -05:00
parent 408494f8de
commit e5329b42e6
3 changed files with 23 additions and 17 deletions
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19
crypto/multiexp/src/lib.rs
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@@ -19,6 +19,8 @@ pub use batch::BatchVerifier;
#[cfg(test)] #[cfg(test)]
mod tests; mod tests;
// Convert scalars to `window`-sized bit groups, as needed to index a table
// This algorithm works for `window <= 8`
pub(crate) fn prep_bits<G: Group>(pairs: &[(G::Scalar, G)], window: u8) -> Vec<Vec<u8>> pub(crate) fn prep_bits<G: Group>(pairs: &[(G::Scalar, G)], window: u8) -> Vec<Vec<u8>>
where where
G::Scalar: PrimeFieldBits, G::Scalar: PrimeFieldBits,
@@ -31,10 +33,9 @@ where
let mut bits = pair.0.to_le_bits(); let mut bits = pair.0.to_le_bits();
groupings.push(vec![0; (bits.len() + (w_usize - 1)) / w_usize]); groupings.push(vec![0; (bits.len() + (w_usize - 1)) / w_usize]);
#[allow(unused_assignments)]
for (i, mut raw_bit) in bits.iter_mut().enumerate() { for (i, mut raw_bit) in bits.iter_mut().enumerate() {
let mut bit = u8::from(*raw_bit); let mut bit = u8::from(*raw_bit);
*raw_bit = false; (*raw_bit).zeroize();
groupings[p][i / w_usize] |= bit << (i % w_usize); groupings[p][i / w_usize] |= bit << (i % w_usize);
bit.zeroize(); bit.zeroize();
@@ -44,20 +45,6 @@ where
groupings groupings
} }
pub(crate) fn prep_tables<G: Group>(pairs: &[(G::Scalar, G)], window: u8) -> Vec<Vec<G>> {
let mut tables = Vec::with_capacity(pairs.len());
for pair in pairs {
let p = tables.len();
tables.push(vec![G::identity(); 2_usize.pow(window.into())]);
let mut accum = G::identity();
for i in 1 .. tables[p].len() {
accum += pair.1;
tables[p][i] = accum;
}
}
tables
}
#[derive(Clone, Copy, PartialEq, Eq, Debug)] #[derive(Clone, Copy, PartialEq, Eq, Debug)]
enum Algorithm { enum Algorithm {
Null, Null,

2
crypto/multiexp/src/pippenger.rs
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@@ -5,6 +5,8 @@ use group::Group;
use crate::prep_bits; use crate::prep_bits;
// Pippenger's algorithm for multiexponentation, as published in the SIAM Journal on Computing
// DOI: 10.1137/0209022
pub(crate) fn pippenger<G: Group>(pairs: &[(G::Scalar, G)], window: u8) -> G pub(crate) fn pippenger<G: Group>(pairs: &[(G::Scalar, G)], window: u8) -> G
where where
G::Scalar: PrimeFieldBits, G::Scalar: PrimeFieldBits,

19
crypto/multiexp/src/straus.rs
View File

@@ -3,8 +3,25 @@ use zeroize::Zeroize;
use ff::PrimeFieldBits; use ff::PrimeFieldBits;
use group::Group; use group::Group;
use crate::{prep_bits, prep_tables}; use crate::prep_bits;
// Create tables for every included point of size 2^window
fn prep_tables<G: Group>(pairs: &[(G::Scalar, G)], window: u8) -> Vec<Vec<G>> {
let mut tables = Vec::with_capacity(pairs.len());
for pair in pairs {
let p = tables.len();
tables.push(vec![G::identity(); 2_usize.pow(window.into())]);
let mut accum = G::identity();
for i in 1 .. tables[p].len() {
accum += pair.1;
tables[p][i] = accum;
}
}
tables
}
// Straus's algorithm for multiexponentation, as published in The American Mathematical Monthly
// DOI: 10.2307/2310929
pub(crate) fn straus<G: Group>(pairs: &[(G::Scalar, G)], window: u8) -> G pub(crate) fn straus<G: Group>(pairs: &[(G::Scalar, G)], window: u8) -> G
where where
G::Scalar: PrimeFieldBits + Zeroize, G::Scalar: PrimeFieldBits + Zeroize,