crypto: Replace BaseFieldElem with FieldElement (#1417)

Author: chfast

lib/evmone_precompiles/ecc.hpp

@@ -26,8 +26,6 @@ template <typename T>
 concept FieldSpec = requires { T::ORDER; };
 
 /// A representation of an element in a prime field.
-///
-/// TODO: Combine with BaseFieldElem.
 template <FieldSpec Spec>
 class FieldElement
 {
@@ -112,6 +110,12 @@ class FieldElement
     {
         return wrap(Fp.mul(a.value_, Fp.inv(b.value_)));
     }
+
+    /// Named 1/x inversion method. Needed in the pairing templates.
+    constexpr auto inv() const noexcept { return wrap(Fp.inv(value_)); }
+
+    /// Named one element. Needed in the pairing templates.
+    static constexpr auto one() noexcept { return FieldElement{1}; }
 };
 
 /// The affine (two coordinates) point on an Elliptic Curve over a prime field.

lib/evmone_precompiles/pairing/bn254/fields.hpp

@@ -10,15 +10,7 @@
 namespace evmmax::bn254
 {
 using namespace intx;
-
-/// Specifies base field value type and modular arithmetic for bn254 curve.
-struct BaseFieldConfig
-{
-    using ValueT = uint256;
-    static constexpr auto MOD_ARITH = ModArith{Curve::FIELD_PRIME};
-    static constexpr auto ONE = MOD_ARITH.to_mont(1);
-};
-using Fq = ecc::BaseFieldElem<BaseFieldConfig>;
+using Fq = Curve::Fp;
 
 // Extension fields implemented based on https://hackmd.io/@jpw/bn254#Field-extension-towers
 
@@ -39,10 +31,10 @@ struct Fq6Config
     using BaseFieldT = Fq;
     using ValueT = Fq2;
     static constexpr uint8_t DEGREE = 3;
-    static constexpr auto ksi = Fq2({Fq::from_int(9_u256), Fq::from_int(1_u256)});
+    static constexpr auto ksi = Fq2({Fq(9_u256), Fq(1_u256)});
     static constexpr auto _3_ksi_inv = Fq2({
-        Fq::from_int(0x2b149d40ceb8aaae81be18991be06ac3b5b4c5e559dbefa33267e6dc24a138e5_u256),
-        Fq::from_int(0x9713b03af0fed4cd2cafadeed8fdf4a74fa084e52d1852e4a2bd0685c315d2_u256),
+        Fq(0x2b149d40ceb8aaae81be18991be06ac3b5b4c5e559dbefa33267e6dc24a138e5_u256),
+        Fq(0x9713b03af0fed4cd2cafadeed8fdf4a74fa084e52d1852e4a2bd0685c315d2_u256),
     });
 };
 using Fq6 = ecc::ExtFieldElem<Fq6Config>;
@@ -110,12 +102,6 @@ constexpr Fq12 multiply(const Fq12& a, const Fq12& b)
     return Fq12({c0, c1});
 }
 
-/// Inverses the base field element
-inline Fq inverse(const Fq& x)
-{
-    return Fq(BaseFieldConfig::MOD_ARITH.inv(x.value()));
-}
-
 /// Inverses the Fq^2 field element
 inline Fq2 inverse(const Fq2& f)
 {

lib/evmone_precompiles/pairing/bn254/pairing.cpp

@@ -145,9 +145,9 @@ std::optional<bool> pairing_check(std::span<const std::pair<Point, ExtPoint>> pa
         }
 
         // Converts points' coefficients in Montgomery form.
-        const auto P_aff = ecc::Point<Fq>{Fq::from_int(p.x), Fq::from_int(p.y)};
-        const auto Q_aff = ecc::Point<Fq2>{Fq2({Fq::from_int(q.x.first), Fq::from_int(q.x.second)}),
-            Fq2({Fq::from_int(q.y.first), Fq::from_int(q.y.second)})};
+        const auto P_aff = ecc::Point<Fq>{Fq(p.x), Fq(p.y)};
+        const auto Q_aff = ecc::Point<Fq2>{
+            Fq2({Fq(q.x.first), Fq(q.x.second)}), Fq2({Fq(q.y.first), Fq(q.y.second)})};
 
         const bool g1_is_inf = is_infinity(P_aff);
         const bool g2_is_inf = g2_is_infinity(Q_aff);

lib/evmone_precompiles/pairing/bn254/utils.hpp

@@ -9,7 +9,7 @@ namespace evmmax::bn254
 {
 consteval Fq2 make_fq2(const uint256& a, const uint256& b) noexcept
 {
-    return Fq2({Fq::from_int(a), Fq::from_int(b)});
+    return Fq2({Fq(a), Fq(b)});
 }
 
 /// Defines coefficients needed for fast Frobenius endomorphism computation.
@@ -77,7 +77,7 @@ constexpr bool is_field_element(const uint256& v)
 constexpr bool is_on_curve(const ecc::Point<Fq>& p) noexcept
 {
     // TODO(C++23): make static
-    constexpr auto B = Fq::from_int(3);
+    constexpr auto B = Fq(3);
 
     const auto x3 = p.x * p.x * p.x;
     const auto y2 = p.y * p.y;
@@ -96,7 +96,7 @@ constexpr bool is_on_twisted_curve(const evmmax::ecc::Point<Fq2>& p)
 /// Verifies that affine point over the base field is infinity.
 constexpr bool is_infinity(const evmmax::ecc::Point<Fq>& p)
 {
-    return p.x.is_zero() && p.y.is_zero();
+    return p.x == 0 && p.y == 0;
 }
 
 /// Verifies that affine point over the Fq^2 extended field is infinity.

lib/evmone_precompiles/pairing/field_template.hpp

@@ -7,65 +7,6 @@
 
 namespace evmmax::ecc
 {
-/// Implements computations over base field defined by prime number.
-/// Wraps around ModArith struct and implements additional functions needed for pairing.
-/// It is a template struct which can be reused for different pairing implementations.
-template <typename ConfigT>
-class BaseFieldElem
-{
-    using ValueT = typename ConfigT::ValueT;
-
-    static constexpr ModArith<ValueT> Fp = ConfigT::MOD_ARITH;
-
-    ValueT m_value;
-
-public:
-    constexpr BaseFieldElem() noexcept = default;
-
-    explicit constexpr BaseFieldElem(const ValueT& v) noexcept : m_value(v) {}
-
-    static constexpr BaseFieldElem from_int(const ValueT& v) noexcept
-    {
-        return BaseFieldElem(Fp.to_mont(v));
-    }
-
-    constexpr const ValueT& value() const noexcept { return m_value; }
-
-    BaseFieldElem inv() const noexcept { return inverse(*this); }
-
-    constexpr bool is_zero() const noexcept { return m_value == 0; }
-
-    static constexpr BaseFieldElem one() noexcept { return BaseFieldElem(ConfigT::ONE); }
-
-    static constexpr BaseFieldElem zero() noexcept { return BaseFieldElem(0); }
-
-    friend constexpr BaseFieldElem operator+(
-        const BaseFieldElem& e1, const BaseFieldElem& e2) noexcept
-    {
-        return BaseFieldElem(Fp.add(e1.m_value, e2.m_value));
-    }
-
-    friend constexpr BaseFieldElem operator-(
-        const BaseFieldElem& e1, const BaseFieldElem& e2) noexcept
-    {
-        return BaseFieldElem(Fp.sub(e1.m_value, e2.m_value));
-    }
-
-    friend constexpr BaseFieldElem operator*(
-        const BaseFieldElem& e1, const BaseFieldElem& e2) noexcept
-    {
-        return BaseFieldElem(Fp.mul(e1.m_value, e2.m_value));
-    }
-
-    friend constexpr BaseFieldElem operator-(const BaseFieldElem& e) noexcept
-    {
-        return BaseFieldElem(Fp.sub(ValueT{0}, e.m_value));
-    }
-
-    friend constexpr bool operator==(
-        const BaseFieldElem& e1, const BaseFieldElem& e2) noexcept = default;
-};
-
 /// Implements extension field over the base field or other extension fields.
 /// It is a template struct which can be reused for different pairing implementations.
 template <typename ConfigT>