Add Invert to MontyForm supertraits (#1226)

Signed-off-by: Andrew Whitehead <cywolf@gmail.com>

Author: andrewwhitehead

src/modular/boxed_monty_form/invert.rs

@@ -64,7 +64,7 @@ impl BoxedMontyParams {
 #[cfg(test)]
 mod tests {
     use crate::{
-        BoxedUint,
+        BoxedUint, Invert,
         modular::{BoxedMontyForm, BoxedMontyParams},
     };
     use hex_literal::hex;
@@ -92,8 +92,11 @@ mod tests {
         let x_mod = BoxedMontyForm::new(x, &params);
 
         let inv = x_mod.invert().unwrap();
-        let res = x_mod * inv;
+        let res = &x_mod * &inv;
 
         assert!(bool::from(res.retrieve().is_one()));
+
+        let inv_trait = Invert::invert(&x_mod).unwrap();
+        assert_eq!(inv_trait, inv);
     }
 }

src/modular/const_monty_form/invert.rs

@@ -95,7 +95,7 @@ impl<MOD: ConstMontyParams<LIMBS>, const LIMBS: usize> Invert for ConstMontyForm
 #[cfg(test)]
 mod tests {
     use super::ConstMontyParams;
-    use crate::{U256, const_monty_form, const_monty_params};
+    use crate::{Invert, U256, const_monty_form, const_monty_params};
 
     const_monty_params!(
         Modulus,
@@ -115,5 +115,8 @@ mod tests {
         let res = x_mod * inv;
 
         assert_eq!(res.retrieve(), U256::ONE);
+
+        let inv_trait = Invert::invert(&x_mod).unwrap();
+        assert_eq!(inv_trait, inv);
     }
 }

src/modular/fixed_monty_form/invert.rs

@@ -91,7 +91,7 @@ impl<const LIMBS: usize> FixedMontyParams<LIMBS> {
 #[cfg(test)]
 mod tests {
     use super::{FixedMontyForm, FixedMontyParams};
-    use crate::{Odd, U256};
+    use crate::{Invert, Odd, U256};
 
     fn params() -> FixedMontyParams<{ U256::LIMBS }> {
         FixedMontyParams::new_vartime(Odd::<U256>::from_be_hex(
@@ -110,5 +110,8 @@ mod tests {
         let res = x_monty * inv;
 
         assert_eq!(res.retrieve(), U256::ONE);
+
+        let inv_trait = Invert::invert(&x_monty).unwrap();
+        assert_eq!(inv_trait, inv);
     }
 }

src/traits.rs

@@ -1155,6 +1155,7 @@ pub trait MontyForm:
     + CtSelect
     + Debug
     + Eq
+    + Invert<Output = CtOption<Self>>
     + Sized
     + Send
     + Sync