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[Zellic Audit] 3.13 make point at infinity valid for p3 #375

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[Zellic Audit] 3.13 make point at infinity valid for p3 #375

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44 changes: 34 additions & 10 deletions bitvm/src/chunk/taps_ext_miller.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ use crate::{
treepp::*,
};
use ark_ff::{AdditiveGroup, Field, PrimeField};
use bitcoin::opcodes::all::OP_ENDIF;
use core::ops::Neg;

use super::wrap_hasher::hash_utils::{hash_fp6, hash_g2acc_with_hashed_le};
Expand Down Expand Up @@ -124,30 +125,36 @@ pub(crate) fn chunk_precompute_p_from_hash(
let mut px: ark_bn254::Fq = ark_bn254::Fq::ONE;
let mut py: ark_bn254::Fq = ark_bn254::Fq::ONE;

let py_is_not_zero = hint_in_p.y != ark_bn254::Fq::ZERO;
if py_is_not_zero {
let is_inf = (hint_in_p.y == ark_bn254::Fq::ZERO) && (hint_in_p.x == ark_bn254::Fq::ZERO);

// avoid panic in hinted_is_on_curve
if hint_in_p.y != ark_bn254::Fq::ZERO {
px = hint_in_p.x;
py = hint_in_p.y;
}

let (on_curve_scr, on_curve_hint) = G1Affine::hinted_is_on_curve(px, py);
if py_is_not_zero {
if hint_in_p.y != ark_bn254::Fq::ZERO {
hints.extend_from_slice(&on_curve_hint);
}

let p = ark_bn254::G1Affine::new_unchecked(px, py);
let (eval_xy, eval_hints) = hinted_from_eval_points(p);

let valid_point = py_is_not_zero && p.is_on_curve();
let valid_point = is_inf || p.is_on_curve();
let mock_pd = ark_bn254::G1Affine::new_unchecked(ark_bn254::Fq::ONE, ark_bn254::Fq::ONE);

let pd = if valid_point {
if hint_in_p.y != ark_bn254::Fq::ZERO && p.is_on_curve() {
hints.extend_from_slice(&eval_hints);
}

let pd = if p.is_on_curve() {
let pdy = p.y.inverse().unwrap();
let pdx = -p.x * pdy;

ark_bn254::G1Affine::new_unchecked(pdx, pdy)
} else if is_inf {
ark_bn254::G1Affine::new_unchecked(ark_bn254::Fq::ZERO, ark_bn254::Fq::ZERO)
} else {
mock_pd
};
Expand All @@ -162,7 +169,19 @@ pub(crate) fn chunk_precompute_p_from_hash(
// [hints, px, py] [pdhash, phash]
{Fq::is_zero_keep_element(0)}
OP_IF // PY = 0
{drop_and_return_scr.clone()}
{Fq::toaltstack()}
{Fq::is_zero_keep_element(0)}
OP_IF // PX = 0
{Fq::fromaltstack()}
// The current implementation of MillerPointOpsStep1 would calculate the correct value if the result
// of PreMillerPrecomputePFromHash for point at infinity was the pair (0,0)
{G1Affine::push(pd)}
{1}
OP_ELSE // PX != 0
{Fq::fromaltstack()}
{drop_and_return_scr.clone()}
OP_ENDIF

OP_ELSE // PY != 0
// [hints, px, py]
{Fq2::copy(0)}
Expand Down Expand Up @@ -694,11 +713,16 @@ mod test {
let p2 = ark_bn254::G1Affine::new_unchecked(ark_bn254::Fq::ONE, ark_bn254::Fq::ZERO);
let p3 = ark_bn254::G1Affine::new_unchecked(ark_bn254::Fq::ZERO, ark_bn254::Fq::ZERO);
let p4 = ark_bn254::G1Affine::new_unchecked(p1.x, p1.x);
let dataset = vec![(p1, false), (p2, true), (p3, true), (p4, true)];
let dataset = vec![(p1, false), (p2, true), (p3, false), (p4, true)];

for (p, disprovable) in dataset {
for (idx, (p, disprovable)) in dataset.into_iter().enumerate() {
let (hint_out, input_is_valid, tap_prex, hint_script) = chunk_precompute_p_from_hash(p);
assert_eq!(input_is_valid, !disprovable);
assert_eq!(
input_is_valid,
!disprovable,
"failed for point p{:?}",
idx + 1
);
let hint_out = DataType::G1Data(hint_out);
let p = DataType::G1Data(p);

Expand Down Expand Up @@ -732,7 +756,7 @@ mod test {
println!("{i:} {:?}", res.final_stack.get(i));
}
}
assert_eq!(res.success, disprovable);
assert_eq!(res.success, disprovable, "failed for point p{:?}", idx + 1);
assert!(res.final_stack.len() == 1);
println!(
"chunk_precompute_p_from_hash disprovable({}) script {} stack {}",
Expand Down