Update to arkworks libraries (#3)

Co-authored-by: Nicholas Ward <npward@berkeley.edu>

src/fields/fp3.rs

@@ -0,0 +1,17 @@
+use crate::fields::{cubic_extension::*, fp::FpVar};
+use ark_ff::fields::{CubicExtParameters, Fp3Parameters, Fp3ParamsWrapper};
+
+/// A cubic extension field constructed over a prime field.
+/// This is the R1CS equivalent of `ark_ff::Fp3<P>`.
+pub type Fp3Var<P> = CubicExtVar<FpVar<<P as Fp3Parameters>::Fp>, Fp3ParamsWrapper<P>>;
+
+impl<P: Fp3Parameters> CubicExtVarParams<FpVar<P::Fp>> for Fp3ParamsWrapper<P> {
+    fn mul_base_field_vars_by_frob_coeff(
+        c1: &mut FpVar<P::Fp>,
+        c2: &mut FpVar<P::Fp>,
+        power: usize,
+    ) {
+        *c1 *= Self::FROBENIUS_COEFF_C1[power % Self::DEGREE_OVER_BASE_PRIME_FIELD];
+        *c2 *= Self::FROBENIUS_COEFF_C2[power % Self::DEGREE_OVER_BASE_PRIME_FIELD];
+    }
+}