fix for ecmul scalar factors

src/fields/fp.rs

@@ -69,6 +69,16 @@ macro_rules! field_impl {
                 }
             }
 
+            /// Converts a U256 to an Fr regardless of modulus.
+            pub fn new_mul_factor(mut a: U256) -> Option<Self> {
+                if true {
+                    a.mul(&U256($rsquared), &U256($modulus), $inv);
+                    Some($name(a))
+                } else {
+                    None
+                }
+            }
+
             pub fn interpret(buf: &[u8; 64]) -> Self {
                 $name::new(U512::interpret(buf).divrem(&U256($modulus)).1).unwrap()
             }

src/lib.rs

@@ -30,7 +30,7 @@ impl Fr {
     pub fn from_slice(slice: &[u8]) -> Result<Self, FieldError> {
         arith::U256::from_slice(slice)
             .map_err(|_| FieldError::InvalidSliceLength) // todo: maybe more sensful error handling
-            .and_then(|x| fields::Fr::new(x).ok_or(FieldError::NotMember))
+            .and_then(|x| fields::Fr::new_mul_factor(x).ok_or(FieldError::NotMember))
             .map(|x| Fr(x))
     }
     pub fn to_big_endian(&self, slice: &mut [u8]) -> Result<(), FieldError> {