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crypto: Move the twisted curve's b coefficient onto E2 #1641

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Merged
chfast merged 1 commit into from
Aug 10, 2026
Merged

crypto: Move the twisted curve's b coefficient onto E2 #1641

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3 changes: 3 additions & 0 deletions lib/evmone_precompiles/bn254.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,9 @@ struct E2
{
using Fp = Fq2;
static constexpr auto A = 0;
/// b/ξ, i.e. Curve::B divided by the Fq⁶ non-residue ξ.
static constexpr Fp B{0x2b149d40ceb8aaae81be18991be06ac3b5b4c5e559dbefa33267e6dc24a138e5_u256,
0x9713b03af0fed4cd2cafadeed8fdf4a74fa084e52d1852e4a2bd0685c315d2_u256};
};

using ExtPoint = ecc::AffinePoint<E2>;
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4 changes: 0 additions & 4 deletions lib/evmone_precompiles/pairing/bn254/fields.hpp
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Expand Up @@ -22,10 +22,6 @@ struct Fq6Config
using ValueT = Fq2;
static constexpr uint8_t DEGREE = 3;
static constexpr auto ksi = Fq2({Fq(9_u256), Fq(1_u256)});
static constexpr auto _3_ksi_inv = Fq2({
Fq(0x2b149d40ceb8aaae81be18991be06ac3b5b4c5e559dbefa33267e6dc24a138e5_u256),
Fq(0x9713b03af0fed4cd2cafadeed8fdf4a74fa084e52d1852e4a2bd0685c315d2_u256),
});
};
using Fq6 = ecc::ExtFieldElem<Fq6Config>;

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2 changes: 1 addition & 1 deletion lib/evmone_precompiles/pairing/bn254/utils.hpp
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Expand Up @@ -49,7 +49,7 @@ constexpr bool is_on_twisted_curve(const ecc::AffinePoint<E2>& p)
const auto x3 = p.x * p.x * p.x;
const auto y2 = p.y * p.y;

return y2 == x3 + Fq6Config::_3_ksi_inv;
return y2 == x3 + E2::B;
}

// Frobenius endomorphism related functions are implemented based on
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