Auto merge of #20 - ebfull:pairing_with, r=ebfull

Add pairing_with API.

I needed this for something I'm doing so I just wrote it.

Closes #8

src/bls12_381/ec.rs

@@ -7,7 +7,8 @@ macro_rules! curve_impl {
         $basefield:ident,
         $scalarfield:ident,
         $uncompressed:ident,
-        $compressed:ident
+        $compressed:ident,
+        $pairing:ident
     ) => {
         #[derive(Copy, Clone, PartialEq, Eq, Debug)]
         pub struct $affine {
@@ -113,6 +114,8 @@ macro_rules! curve_impl {
             type Projective = $projective;
             type Uncompressed = $uncompressed;
             type Compressed = $compressed;
+            type Pair = $pairing;
+            type PairingResult = Fq12;
 
             fn zero() -> Self {
                 $affine {
@@ -155,6 +158,10 @@ macro_rules! curve_impl {
                 $prepared::from_affine(*self)
             }
 
+            fn pairing_with(&self, other: &Self::Pair) -> Self::PairingResult {
+                self.perform_pairing(other)
+            }
+
             fn into_projective(&self) -> $projective {
                 (*self).into()
             }
@@ -574,10 +581,11 @@ macro_rules! curve_impl {
 
 pub mod g1 {
     use rand::{Rand, Rng};
-    use super::super::{Fq, Fr, FrRepr, FqRepr};
-    use ::{CurveProjective, CurveAffine, PrimeField, SqrtField, PrimeFieldRepr, Field, BitIterator, EncodedPoint, GroupDecodingError};
+    use super::g2::G2Affine;
+    use super::super::{Fq, Fr, FrRepr, FqRepr, Fq12};
+    use ::{CurveProjective, CurveAffine, PrimeField, SqrtField, PrimeFieldRepr, Field, BitIterator, EncodedPoint, GroupDecodingError, Engine};
 
-    curve_impl!("G1", G1, G1Affine, G1Prepared, Fq, Fr, G1Uncompressed, G1Compressed);
+    curve_impl!("G1", G1, G1Affine, G1Prepared, Fq, Fr, G1Uncompressed, G1Compressed, G2Affine);
 
     #[derive(Copy)]
     pub struct G1Uncompressed([u8; 96]);
@@ -828,6 +836,10 @@ pub mod g1 {
         fn get_coeff_b() -> Fq {
             super::super::fq::B_COEFF
         }
+
+        fn perform_pairing(&self, other: &G2Affine) -> Fq12 {
+            super::super::Bls12::pairing(*self, *other)
+        }
     }
 
     impl G1 {
@@ -1122,10 +1134,11 @@ pub mod g1 {
 
 pub mod g2 {
     use rand::{Rand, Rng};
-    use super::super::{Fq2, Fr, Fq, FrRepr, FqRepr};
-    use ::{CurveProjective, CurveAffine, PrimeField, SqrtField, PrimeFieldRepr, Field, BitIterator, EncodedPoint, GroupDecodingError};
+    use super::super::{Fq2, Fr, Fq, FrRepr, FqRepr, Fq12};
+    use super::g1::G1Affine;
+    use ::{CurveProjective, CurveAffine, PrimeField, SqrtField, PrimeFieldRepr, Field, BitIterator, EncodedPoint, GroupDecodingError, Engine};
 
-    curve_impl!("G2", G2, G2Affine, G2Prepared, Fq2, Fr, G2Uncompressed, G2Compressed);
+    curve_impl!("G2", G2, G2Affine, G2Prepared, Fq2, Fr, G2Uncompressed, G2Compressed, G1Affine);
 
     #[derive(Copy)]
     pub struct G2Uncompressed([u8; 192]);
@@ -1403,6 +1416,10 @@ pub mod g2 {
                 c1: super::super::fq::B_COEFF
             }
         }
+
+        fn perform_pairing(&self, other: &G1Affine) -> Fq12 {
+            super::super::Bls12::pairing(*other, *self)
+        }
     }
 
     impl G2 {

src/lib.rs

@@ -42,13 +42,13 @@ pub trait Engine {
     type G1: CurveProjective<Base=Self::Fq, Scalar=Self::Fr, Affine=Self::G1Affine> + From<Self::G1Affine>;
 
     /// The affine representation of an element in G1.
-    type G1Affine: CurveAffine<Base=Self::Fq, Scalar=Self::Fr, Projective=Self::G1> + From<Self::G1>;
+    type G1Affine: CurveAffine<Base=Self::Fq, Scalar=Self::Fr, Projective=Self::G1, Pair=Self::G2Affine, PairingResult=Self::Fqk> + From<Self::G1>;
 
     /// The projective representation of an element in G2.
     type G2: CurveProjective<Base=Self::Fqe, Scalar=Self::Fr, Affine=Self::G2Affine> + From<Self::G2Affine>;
 
     /// The affine representation of an element in G2.
-    type G2Affine: CurveAffine<Base=Self::Fqe, Scalar=Self::Fr, Projective=Self::G2> + From<Self::G2>;
+    type G2Affine: CurveAffine<Base=Self::Fqe, Scalar=Self::Fr, Projective=Self::G2, Pair=Self::G1Affine, PairingResult=Self::Fqk> + From<Self::G2>;
 
     /// The base field that hosts G1.
     type Fq: PrimeField + SqrtField;
@@ -172,6 +172,8 @@ pub trait CurveAffine: Copy +
     type Prepared: Clone + Send + Sync + 'static;
     type Uncompressed: EncodedPoint<Affine=Self>;
     type Compressed: EncodedPoint<Affine=Self>;
+    type Pair: CurveAffine<Pair=Self>;
+    type PairingResult: Field;
 
     /// Returns the additive identity.
     fn zero() -> Self;
@@ -192,6 +194,9 @@ pub trait CurveAffine: Copy +
     /// Prepares this element for pairing purposes.
     fn prepare(&self) -> Self::Prepared;
 
+    /// Perform a pairing
+    fn pairing_with(&self, other: &Self::Pair) -> Self::PairingResult;
+
     /// Converts this element into its affine representation.
     fn into_projective(&self) -> Self::Projective;
 

src/tests/engine.rs

@@ -6,6 +6,14 @@ pub fn engine_tests<E: Engine>()
 {
     let mut rng = XorShiftRng::from_seed([0x5dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
     
+    for _ in 0..10 {
+        let a = E::G1::rand(&mut rng).into_affine();
+        let b = E::G2::rand(&mut rng).into_affine();
+
+        assert!(a.pairing_with(&b) == b.pairing_with(&a));
+        assert!(a.pairing_with(&b) == E::pairing(a, b));
+    }
+
     for _ in 0..1000 {
         let z1 = E::G1Affine::zero().prepare();
         let z2 = E::G2Affine::zero().prepare();