`skyscraper/bn254-multiplier/src/utils`: tighter bounds

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Refactor
Clarity
Mostly clear
Activity status
Stale
Tech stack
rust
Domain
cryptography, testing-qa

Research direction

Start in skyscraper/bn254-multiplier/src/utils.rs around line 223 and read the div_p_6b_underapprox Kani proof, including the existing assertions and U64_P_MULTIPLES data. Run the proof to establish its current bounds, then determine and encode tighter bounds so the proof passes without the TODO. Done means the underapproximation has stronger verified bounds.

Written by the indexing model from the issue text.

Description

to do tracker

On 2026-03-17 in ba92f89 “Merge pull request #320 from worldfnd/xr/subred”:

tighter bounds

        assert!(x >= r);
        assert!(le256([0, 0, 0, x - r], U64_2P));
    }

    #[kani::proof]
    // TODO tighter bounds
    fn div_p_6b_underapprox() {
        let x: u64 = kani::any();
        let q = div_p_6b(x);

        let r = U64_P_MULTIPLES[q as usize][3];

From skyscraper/bn254-multiplier/src/utils.rs:223

Dominant language
Noir
Stars
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Forks
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Avg merge
1d 34m
Merged PRs (30d)
6

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