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refactor: affine representation of BLS group elements #55

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refactor: affine representation of BLS group elements #55

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2 changes: 1 addition & 1 deletion Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ version = "0.1.0"
edition = "2021"

[dependencies]
blst = "0.3.11"
blst = { git = "https://github.com/jacobkaufmann/blst.git", branch = "feat-rust-affines-from-affines" }
hex = { version = "0.4.3", optional = true }
rand = { version = "0.8.5", optional = true }
serde = { version = "1.0.189", features = ["derive"], optional = true }
Expand Down
101 changes: 47 additions & 54 deletions src/bls.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,13 +9,13 @@ use blst::{
blst_bendian_from_scalar, blst_final_exp, blst_fp12, blst_fp12_is_one, blst_fp12_mul, blst_fr,
blst_fr_add, blst_fr_cneg, blst_fr_eucl_inverse, blst_fr_from_scalar, blst_fr_from_uint64,
blst_fr_lshift, blst_fr_mul, blst_fr_rshift, blst_fr_sub, blst_lendian_from_scalar,
blst_miller_loop, blst_p1, blst_p1_add, blst_p1_affine, blst_p1_affine_in_g1, blst_p1_cneg,
blst_p1_compress, blst_p1_from_affine, blst_p1_mult, blst_p1_to_affine, blst_p1_uncompress,
blst_p2, blst_p2_add, blst_p2_affine, blst_p2_affine_in_g2, blst_p2_cneg, blst_p2_compress,
blst_p2_from_affine, blst_p2_mult, blst_p2_to_affine, blst_p2_uncompress, blst_scalar,
blst_scalar_fr_check, blst_scalar_from_bendian, blst_scalar_from_fr, blst_sha256,
blst_uint64_from_fr, p1_affines, p2_affines, BLS12_381_G1, BLS12_381_G2, BLS12_381_NEG_G1,
BLS12_381_NEG_G2, BLST_ERROR,
blst_miller_loop, blst_p1, blst_p1_add, blst_p1_affine, blst_p1_affine_compress,
blst_p1_affine_in_g1, blst_p1_cneg, blst_p1_from_affine, blst_p1_mult, blst_p1_to_affine,
blst_p1_uncompress, blst_p2, blst_p2_add, blst_p2_affine, blst_p2_affine_compress,
blst_p2_affine_in_g2, blst_p2_cneg, blst_p2_from_affine, blst_p2_mult, blst_p2_to_affine,
blst_p2_uncompress, blst_scalar, blst_scalar_fr_check, blst_scalar_from_bendian,
blst_scalar_from_fr, blst_sha256, blst_uint64_from_fr, p1_affines, p2_affines, BLS12_381_G1,
BLS12_381_G2, BLS12_381_NEG_G1, BLS12_381_NEG_G2, BLST_ERROR,
};

#[derive(Clone, Copy, Debug)]
Expand Down Expand Up @@ -380,26 +380,18 @@ macro_rules! impl_group {
#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
#[repr(transparent)]
pub struct $p {
element: $gelt,
element: $affine,
}

impl $p {
// TODO: make available as `const`
pub fn generator() -> Self {
let mut out = MaybeUninit::<$gelt>::uninit();
unsafe {
$from_affine(out.as_mut_ptr(), &$gen);
Self::from(out.assume_init())
}
unsafe { $gen.into() }
}

// TODO: make available as `const`
pub fn neg_generator() -> Self {
let mut out = MaybeUninit::<$gelt>::uninit();
unsafe {
$from_affine(out.as_mut_ptr(), &$neg_gen);
Self::from(out.assume_init())
}
unsafe { $neg_gen.into() }
}

#[allow(dead_code)]
Expand All @@ -421,9 +413,9 @@ macro_rules! impl_group {

let points = unsafe {
// NOTE: we can perform the cast given `repr(transparent)` for the struct.
slice::from_raw_parts(points.as_ref().as_ptr() as *const $gelt, n)
slice::from_raw_parts(points.as_ref().as_ptr() as *const $affine, n)
};
let points = $affines::from(points);
let points = $affines::new(points);

let scalar_iter = scalars.as_ref().iter().take(n);
let mut scalars = Vec::with_capacity(n * Fr::BYTES);
Expand All @@ -432,19 +424,28 @@ macro_rules! impl_group {
}

let lincomb = points.mult(&scalars, 255);
lincomb.into()
}
}

Self { element: lincomb }
impl From<$affine> for $p {
fn from(element: $affine) -> Self {
Self { element }
}
}

impl From<$gelt> for $p {
fn from(element: $gelt) -> Self {
Self { element }
let mut out = MaybeUninit::<$affine>::uninit();
unsafe {
$to_affine(out.as_mut_ptr(), &element);
out.assume_init().into()
}
}
}

impl AsRef<$gelt> for $p {
fn as_ref(&self) -> &$gelt {
impl AsRef<$affine> for $p {
fn as_ref(&self) -> &$affine {
&self.element
}
}
Expand All @@ -453,12 +454,14 @@ macro_rules! impl_group {
type Output = Self;

fn add(self, rhs: Self) -> Self::Output {
let mut tmpl = MaybeUninit::<$gelt>::uninit();
let mut tmpr = MaybeUninit::<$gelt>::uninit();
let mut out = MaybeUninit::<$gelt>::uninit();
unsafe {
$add(out.as_mut_ptr(), &self.element, &rhs.element);
Self {
element: out.assume_init(),
}
$from_affine(tmpl.as_mut_ptr(), &self.element);
$from_affine(tmpr.as_mut_ptr(), &rhs.element);
$add(out.as_mut_ptr(), tmpl.as_ptr(), tmpr.as_ptr());
out.assume_init().into()
}
}
}
Expand All @@ -467,8 +470,11 @@ macro_rules! impl_group {
type Output = Self;

fn neg(mut self) -> Self::Output {
let mut tmp = MaybeUninit::<$gelt>::uninit();
unsafe {
$neg(&mut self.element, true);
$from_affine(tmp.as_mut_ptr(), &self.element);
$neg(tmp.as_mut_ptr(), true);
$to_affine(&mut self.element, tmp.as_ptr());
}
self
}
Expand All @@ -482,8 +488,9 @@ macro_rules! impl_group {
let mut out = MaybeUninit::<$gelt>::uninit();
unsafe {
blst_scalar_from_fr(&mut scalar, &rhs.element);
$mul(out.as_mut_ptr(), &self.element, scalar.b.as_ptr(), 255);
$p::from(out.assume_init())
$from_affine(out.as_mut_ptr(), &self.element);
$mul(out.as_mut_ptr(), out.as_ptr(), scalar.b.as_ptr(), 255);
out.assume_init().into()
}
}
}
Expand All @@ -506,27 +513,23 @@ macro_rules! impl_group {
type Error = ECGroupError;

fn decompress(compressed: impl AsRef<[u8]>) -> Result<Self, Self::Error> {
let mut affine = MaybeUninit::<$affine>::uninit();
let mut out = MaybeUninit::<$gelt>::uninit();
let mut out = MaybeUninit::<$affine>::uninit();
unsafe {
// NOTE: uncompress performs a curve check but not a subgroup check. if that changes,
// then we should encounter `unreachable` for `BLST_POINT_NOT_IN_GROUP` in tests.
match $uncompress(affine.as_mut_ptr(), compressed.as_ref().as_ptr()) {
match $uncompress(out.as_mut_ptr(), compressed.as_ref().as_ptr()) {
BLST_ERROR::BLST_SUCCESS => {}
BLST_ERROR::BLST_BAD_ENCODING => return Err(ECGroupError::InvalidEncoding),
BLST_ERROR::BLST_POINT_NOT_ON_CURVE => {
return Err(ECGroupError::NotOnCurve)
}
other => unreachable!("{other:?}"),
}
if !$affine_in_group(affine.as_ptr()) {
if !$affine_in_group(out.as_ptr()) {
return Err(ECGroupError::NotInGroup);
}

$from_affine(out.as_mut_ptr(), affine.as_ptr());
Ok(Self {
element: out.assume_init(),
})
Ok(out.assume_init().into())
}
}
}
Expand All @@ -546,7 +549,7 @@ impl_group!(
blst_p1_cneg,
blst_p1_mult,
blst_p1_affine_in_g1,
blst_p1_compress,
blst_p1_affine_compress,
blst_p1_uncompress,
48
);
Expand All @@ -564,32 +567,22 @@ impl_group!(
blst_p2_cneg,
blst_p2_mult,
blst_p2_affine_in_g2,
blst_p2_compress,
blst_p2_affine_compress,
blst_p2_uncompress,
96
);

pub fn verify_pairings((a1, a2): (P1, P2), (b1, b2): (P1, P2)) -> bool {
let mut a1_neg_affine = MaybeUninit::<blst_p1_affine>::uninit();
let mut a2_affine = MaybeUninit::<blst_p2_affine>::uninit();

let mut b1_affine = MaybeUninit::<blst_p1_affine>::uninit();
let mut b2_affine = MaybeUninit::<blst_p2_affine>::uninit();
let neg_a1 = -a1;

let mut e1 = MaybeUninit::<blst_fp12>::uninit();
let mut e2 = MaybeUninit::<blst_fp12>::uninit();
let mut prod = MaybeUninit::<blst_fp12>::uninit();
let mut exp = MaybeUninit::<blst_fp12>::uninit();

unsafe {
blst_p1_to_affine(a1_neg_affine.as_mut_ptr(), &a1.neg().element);
blst_p2_to_affine(a2_affine.as_mut_ptr(), &a2.element);

blst_p1_to_affine(b1_affine.as_mut_ptr(), &b1.element);
blst_p2_to_affine(b2_affine.as_mut_ptr(), &b2.element);

blst_miller_loop(e1.as_mut_ptr(), a2_affine.as_ptr(), a1_neg_affine.as_ptr());
blst_miller_loop(e2.as_mut_ptr(), b2_affine.as_ptr(), b1_affine.as_ptr());
blst_miller_loop(e1.as_mut_ptr(), &a2.element, &neg_a1.element);
blst_miller_loop(e2.as_mut_ptr(), &b2.element, &b1.element);

blst_fp12_mul(prod.as_mut_ptr(), e1.as_ptr(), e2.as_ptr());
blst_final_exp(exp.as_mut_ptr(), prod.as_ptr());
Expand Down
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