From 3734552cf3cb352390e260f65435b6a4f9573277 Mon Sep 17 00:00:00 2001
From: cdetrio <cdetrio@gmail.com>
Date: Thu, 7 Sep 2017 10:50:56 +0200
Subject: [PATCH 1/3] convert from Montgomery representation

---
 src/fields/fp.rs | 6 ++++++
 src/lib.rs       | 7 +++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/fields/fp.rs b/src/fields/fp.rs
index bbbfeada..6539d5e6 100644
--- a/src/fields/fp.rs
+++ b/src/fields/fp.rs
@@ -80,6 +80,12 @@ macro_rules! field_impl {
                 U256($modulus)
             }
 
+            #[inline]
+            #[allow(dead_code)]
+            pub fn inv(&self) -> u64 {
+                $inv
+            }
+
             pub fn raw(&self) -> &U256 {
                 &self.0
             }
diff --git a/src/lib.rs b/src/lib.rs
index 984c1334..00e5e206 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -92,8 +92,11 @@ impl Fq {
             .map(|x| Fq(x))
     }
     pub fn to_big_endian(&self, slice: &mut [u8]) -> Result<(), FieldError> {
-        self.0.raw().to_big_endian(slice).map_err(|_| FieldError::InvalidSliceLength)
-    }    
+        let mut a: arith::U256 = self.0.into();
+        // convert from Montgomery representation
+        a.mul(&fields::Fq::one().raw(), &fields::Fq::modulus(), self.0.inv());
+        a.to_big_endian(slice).map_err(|_| FieldError::InvalidSliceLength)
+    }
 }
 
 impl Add<Fq> for Fq {

From 7002225d7648c1f5072f10e8f70b8e2efd5b0c2a Mon Sep 17 00:00:00 2001
From: cdetrio <cdetrio@gmail.com>
Date: Thu, 7 Sep 2017 10:58:43 +0200
Subject: [PATCH 2/3] fix for ecmul scalar factors

---
 src/fields/fp.rs | 10 ++++++++++
 src/lib.rs       |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/fields/fp.rs b/src/fields/fp.rs
index 6539d5e6..625be0c0 100644
--- a/src/fields/fp.rs
+++ b/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()
             }
diff --git a/src/lib.rs b/src/lib.rs
index 00e5e206..2ff09d36 100644
--- a/src/lib.rs
+++ b/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> {

From 624c60be56b6ee88272020b24d1291ba5cc67aab Mon Sep 17 00:00:00 2001
From: cdetrio <cdetrio@gmail.com>
Date: Fri, 8 Sep 2017 07:40:09 +0200
Subject: [PATCH 3/3] public arith module

---
 src/lib.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 2ff09d36..84ca22d3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,7 +2,7 @@ extern crate rand;
 extern crate rustc_serialize;
 extern crate byteorder;
 
-mod arith;
+pub mod arith;
 mod fields;
 mod groups;