Implement F::characteristic

Author: sebastiencs

ec/src/models/short_weierstrass_jacobian.rs

@@ -142,7 +142,9 @@ impl<P: Parameters> GroupAffine<P> {
     /// Checks if `self` is in the subgroup having order that equaling that of
     /// `P::ScalarField`.
     pub fn is_in_correct_subgroup_assuming_on_curve(&self) -> bool {
-        self.mul_bits(BitIteratorBE::new(P::ScalarField::characteristic()))
+        use core::convert::TryInto;
+        let characteristic = P::ScalarField::characteristic();
+        self.mul_bits(BitIteratorBE::new(&ark_ff::biginteger::to_64x4(characteristic.try_into().unwrap())))
             .is_zero()
     }
 }

ec/src/models/twisted_edwards_extended.rs

@@ -110,7 +110,9 @@ impl<P: Parameters> GroupAffine<P> {
     /// Checks that the current point is in the prime order subgroup given
     /// the point on the curve.
     pub fn is_in_correct_subgroup_assuming_on_curve(&self) -> bool {
-        self.mul_bits(BitIteratorBE::new(P::ScalarField::characteristic()))
+        use core::convert::TryInto;
+        let characteristic = P::ScalarField::characteristic();
+        self.mul_bits(BitIteratorBE::new(&ark_ff::biginteger::to_64x4(characteristic.try_into().unwrap())))
             .is_zero()
     }
 }

ff/src/fields/mod.rs

@@ -123,7 +123,7 @@ pub trait Field:
 
     /// Returns the characteristic of the field,
     /// in little-endian representation.
-    fn characteristic() -> &'static [u64] {
+    fn characteristic() -> &'static [u32] {
         Self::BasePrimeField::characteristic()
     }
 

ff/src/fields/models/fp12_2over3over2.rs

@@ -3,7 +3,7 @@ use crate::{
     fields::{fp6_3over2::*, Field, Fp2, Fp2Parameters},
     One,
 };
-use core::marker::PhantomData;
+use core::{convert::TryInto, marker::PhantomData};
 use core::ops::{AddAssign, SubAssign};
 
 type Fp2Params<P> = <<P as Fp12Parameters>::Fp6Params as Fp6Parameters>::Fp2Params;
@@ -135,7 +135,8 @@ impl<P: Fp12Parameters> Fp12<P> {
         // Faster Squaring in the Cyclotomic Subgroup of Sixth Degree Extensions
         // - Robert Granger and Michael Scott
         //
-        if characteristic_square_mod_6_is_one(Self::characteristic()) {
+        let characteristic = Self::characteristic();
+        if characteristic_square_mod_6_is_one(&super::to_64x4(characteristic.try_into().unwrap())) {
             let fp2_nr = <P::Fp6Params as Fp6Parameters>::mul_fp2_by_nonresidue;
 
             let r0 = &self.c0.c0;

ff/src/fields/models/webnode_new.rs

@@ -1121,10 +1121,6 @@ impl<C: Fp256Parameters> FromBytes for NewFp256<C> {
         })
     }
 }
-    // + core::iter::Sum<Self>
-    // + for<'a> core::iter::Sum<&'a Self>
-    // + core::iter::Product<Self>
-    // + for<'a> core::iter::Product<&'a Self>
 
 impl<C: Fp256Parameters> Field for NewFp256<C> {
     type BasePrimeField = Self;
@@ -1150,9 +1146,8 @@ impl<C: Fp256Parameters> Field for NewFp256<C> {
         self
     }
     #[inline]
-    fn characteristic() -> &'static [u64] {
-        todo!()
-        // P::MODULUS.as_ref()
+    fn characteristic() -> &'static [u32] {
+        &C::MODULUS.0
     }
     #[inline]
     fn from_random_bytes_with_flags<F: Flags>(bytes: &[u8]) -> Option<(Self, F)> {