diff --git a/examples/joux.rs b/examples/joux.rs
index ba1a6e0..88cb53b 100644
--- a/examples/joux.rs
+++ b/examples/joux.rs
@@ -1,6 +1,6 @@
 extern crate bn;
 extern crate rand;
-use bn::{Fr, G1, G2, pairing};
+use bn::{Group, Fr, G1, G2, pairing};
 
 fn main() {
     let rng = &mut rand::thread_rng();
diff --git a/src/fields/fp.rs b/src/fields/fp.rs
index 3c47b9f..b881f52 100644
--- a/src/fields/fp.rs
+++ b/src/fields/fp.rs
@@ -17,6 +17,7 @@ pub trait FpParams {
     fn one() -> U256;
 }
 
+#[repr(C)]
 pub struct Fp<P: FpParams>(U256, PhantomData<P>);
 impl<P: FpParams> Copy for Fp<P> { }
 impl<P: FpParams> Clone for Fp<P> {
diff --git a/src/fields/fq12.rs b/src/fields/fq12.rs
index cb11e2e..d8d0dbc 100644
--- a/src/fields/fq12.rs
+++ b/src/fields/fq12.rs
@@ -24,6 +24,7 @@ fn frobenius_coeffs_c1(power: usize) -> Fq2 {
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[repr(C)]
 pub struct Fq12 {
     c0: Fq6,
     c1: Fq6
diff --git a/src/fields/fq2.rs b/src/fields/fq2.rs
index 958a53c..551842e 100644
--- a/src/fields/fq2.rs
+++ b/src/fields/fq2.rs
@@ -20,6 +20,7 @@ pub fn fq2_nonresidue() -> Fq2 {
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[repr(C)]
 pub struct Fq2 {
     c0: Fq,
     c1: Fq
diff --git a/src/fields/fq6.rs b/src/fields/fq6.rs
index 810e3da..39b91ed 100644
--- a/src/fields/fq6.rs
+++ b/src/fields/fq6.rs
@@ -40,6 +40,7 @@ fn frobenius_coeffs_c2(n: usize) -> Fq2 {
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[repr(C)]
 pub struct Fq6 {
     pub c0: Fq2,
     pub c1: Fq2,
diff --git a/src/groups/mod.rs b/src/groups/mod.rs
index bdf5889..6fef217 100644
--- a/src/groups/mod.rs
+++ b/src/groups/mod.rs
@@ -32,6 +32,7 @@ pub trait GroupParams: Sized {
     fn coeff_b() -> Self::Base;
 }
 
+#[repr(C)]
 pub struct G<P: GroupParams> {
     x: P::Base,
     y: P::Base,
diff --git a/src/lib.rs b/src/lib.rs
index 255f122..c28f555 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -13,6 +13,7 @@ use std::ops::{Add, Sub, Mul, Neg};
 use rand::Rng;
 
 #[derive(Copy, Clone, PartialEq, Eq, RustcDecodable, RustcEncodable)]
+#[repr(C)]
 pub struct Fr(fields::Fr);
 
 impl Fr {
@@ -22,6 +23,7 @@ impl Fr {
     pub fn pow(&self, exp: Fr) -> Self { Fr(self.0.pow(exp.0)) }
     pub fn from_str(s: &str) -> Option<Self> { fields::Fr::from_str(s).map(|e| Fr(e)) }
     pub fn inverse(&self) -> Option<Self> { self.0.inverse().map(|e| Fr(e)) }
+    pub fn is_zero(&self) -> bool { self.0.is_zero() }
 }
 
 impl Add<Fr> for Fr {
@@ -48,13 +50,22 @@ impl Mul for Fr {
     fn mul(self, other: Fr) -> Fr { Fr(self.0 * other.0) }
 }
 
+pub trait Group: Copy + Clone + PartialEq + Eq + Sized + Add<Self> + Sub<Self> + Neg + Mul<Fr> {
+    fn zero() -> Self;
+    fn one() -> Self;
+    fn random<R: Rng>(rng: &mut R) -> Self;
+    fn is_zero(&self) -> bool;
+}
+
 #[derive(Copy, Clone, PartialEq, Eq, RustcDecodable, RustcEncodable)]
+#[repr(C)]
 pub struct G1(groups::G1);
 
-impl G1 {
-    pub fn zero() -> Self { G1(groups::G1::zero()) }
-    pub fn one() -> Self { G1(groups::G1::one()) }
-    pub fn random<R: Rng>(rng: &mut R) -> Self { G1(groups::G1::random(rng)) }
+impl Group for G1 {
+    fn zero() -> Self { G1(groups::G1::zero()) }
+    fn one() -> Self { G1(groups::G1::one()) }
+    fn random<R: Rng>(rng: &mut R) -> Self { G1(groups::G1::random(rng)) }
+    fn is_zero(&self) -> bool { self.0.is_zero() }
 }
 
 impl Add<G1> for G1 {
@@ -82,12 +93,14 @@ impl Mul<Fr> for G1 {
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, RustcDecodable, RustcEncodable)]
+#[repr(C)]
 pub struct G2(groups::G2);
 
-impl G2 {
-    pub fn zero() -> Self { G2(groups::G2::zero()) }
-    pub fn one() -> Self { G2(groups::G2::one()) }
-    pub fn random<R: Rng>(rng: &mut R) -> Self { G2(groups::G2::random(rng)) }
+impl Group for G2 {
+    fn zero() -> Self { G2(groups::G2::zero()) }
+    fn one() -> Self { G2(groups::G2::one()) }
+    fn random<R: Rng>(rng: &mut R) -> Self { G2(groups::G2::random(rng)) }
+    fn is_zero(&self) -> bool { self.0.is_zero() }
 }
 
 impl Add<G2> for G2 {
@@ -115,6 +128,7 @@ impl Mul<Fr> for G2 {
 }
 
 #[derive(Copy, Clone, PartialEq, Eq)]
+#[repr(C)]
 pub struct Gt(fields::Fq12);
 
 impl Gt {