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fix(zk): overflow in noise tests

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This commit is contained in:
Nicolas Sarlin
2025-06-04 16:23:27 +02:00
committed by Nicolas Sarlin
parent be1ade6dd2
commit c94a76a85a
2 changed files with 36 additions and 12 deletions
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21
tfhe-zk-pok/src/proofs/mod.rs
View File

@@ -421,6 +421,8 @@ pub mod pke_v2;
mod test {
#![allow(non_snake_case)]
use std::fmt::Display;
use std::num::Wrapping;
use std::ops::Sub;
use ark_ec::{short_weierstrass, CurveConfig};
use ark_ff::UniformRand;
@@ -477,6 +479,17 @@ mod test {
c
}
/// Wrapper that panics on overflow even in release mode
pub(super) struct Strict<Num>(pub Num);
impl Sub for Strict<u128> {
type Output = Strict<u128>;
fn sub(self, rhs: Self) -> Self::Output {
Strict(self.0.checked_sub(rhs.0).unwrap())
}
}
/// Parameters needed for a PKE zk proof test
#[derive(Copy, Clone)]
pub(super) struct PkeTestParameters {
@@ -581,7 +594,13 @@ mod test {
let mut a = (0..d).map(|_| rng.gen::<i64>()).collect::<Vec<_>>();
let b = a.iter().zip(&self.s).map(|(ai, si)| ai * si).sum::<i64>() + e;
let b = a
.iter()
.zip(&self.s)
.map(|(ai, si)| Wrapping(ai * si))
.sum::<Wrapping<i64>>()
.0
+ e;
a.push(b);
a

27
tfhe-zk-pok/src/proofs/pke_v2.rs
View File

@@ -2885,12 +2885,14 @@ mod tests {
};
let B_with_slack_squared = inf_norm_bound_to_euclidean_squared(B, d + k);
let B_with_slack = B_with_slack_squared.isqrt() as u64;
let B_with_slack = u64::try_from(B_with_slack_squared.isqrt()).unwrap();
let bound = match slack_mode {
let coeff_at_bound = match slack_mode {
// The slack is maximal, any term above B+slack should be refused
BoundTestSlackMode::Max => B_with_slack as i64,
BoundTestSlackMode::Max => i64::try_from(B_with_slack).unwrap(),
// The actual accepted bound depends on the content of the test vector
// To create a bound testcase, we have to modify the tested coeff such that the
// squared norm 2 of the noise vector is equal to B_with_slack_squared
BoundTestSlackMode::Avg => {
let e_sqr_norm = testcase
.e1
@@ -2899,24 +2901,27 @@ mod tests {
.map(|x| sqr(x.unsigned_abs()))
.sum::<u128>();
let orig_value = match coeff_type {
let orig_coeff = match coeff_type {
TestedCoeffType::E1 => testcase.e1[tested_idx],
TestedCoeffType::E2 => testcase.e2[tested_idx],
};
let bound_squared =
B_with_slack_squared - (e_sqr_norm - sqr(orig_value as u64));
bound_squared.isqrt() as i64
let sqr_norm_without_tested_coeff =
Strict(e_sqr_norm) - Strict(sqr(orig_coeff.unsigned_abs()));
let sqr_modified_coeff =
Strict(B_with_slack_squared) - sqr_norm_without_tested_coeff;
i64::try_from(sqr_modified_coeff.0.isqrt()).unwrap()
}
// There is no slack effect, any term above B should be refused
BoundTestSlackMode::Min => B as i64,
BoundTestSlackMode::Min => i64::try_from(B).unwrap(),
};
let tested_term = bound + offset_type.offset();
// Depending on what we want to test, add -1, 0 or 1 to the coeff at the bound
let tested_coeff = coeff_at_bound + offset_type.offset();
match coeff_type {
TestedCoeffType::E1 => testcase.e1[tested_idx] = tested_term,
TestedCoeffType::E2 => testcase.e2[tested_idx] = tested_term,
TestedCoeffType::E1 => testcase.e1[tested_idx] = tested_coeff,
TestedCoeffType::E2 => testcase.e2[tested_idx] = tested_coeff,
};
Self {