From 7fb2ebf3f12f043d7bd12f43500dc2bd133df573 Mon Sep 17 00:00:00 2001
From: Nishant Das <nish1993@hotmail.com>
Date: Fri, 21 Jun 2019 08:43:03 +0530
Subject: [PATCH] Add Functions for Compressed and Uncompressed HashG2 With
 Domain (#2833)

* add tests

* gaz

* lint
---
 shared/bls/BUILD.bazel |  6 +++++-
 shared/bls/bls.go      | 13 +++++++++++++
 shared/bls/bls_test.go | 18 ++++++++++++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/shared/bls/BUILD.bazel b/shared/bls/BUILD.bazel
index 686f227230..4006f09086 100644
--- a/shared/bls/BUILD.bazel
+++ b/shared/bls/BUILD.bazel
@@ -7,6 +7,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//shared/bytesutil:go_default_library",
+        "@com_github_phoreproject_bls//:go_default_library",
         "@com_github_phoreproject_bls//g1pubs:go_default_library",
     ],
 )
@@ -15,5 +16,8 @@ go_test(
     name = "go_default_test",
     srcs = ["bls_test.go"],
     embed = [":go_default_library"],
-    deps = ["//shared/bytesutil:go_default_library"],
+    deps = [
+        "//shared/bytesutil:go_default_library",
+        "@com_github_phoreproject_bls//:go_default_library",
+    ],
 )
diff --git a/shared/bls/bls.go b/shared/bls/bls.go
index 859f80c1e5..da6541b512 100644
--- a/shared/bls/bls.go
+++ b/shared/bls/bls.go
@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/phoreproject/bls"
 	g1 "github.com/phoreproject/bls/g1pubs"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"
 )
@@ -125,6 +126,18 @@ func AggregateSignatures(sigs []*Signature) *Signature {
 	return &Signature{val: g1.AggregateSignatures(ss)}
 }
 
+// HashG2WithDomainCompressed returns the compressed hash.
+func HashG2WithDomainCompressed(msg [32]byte, domain uint64) [96]byte {
+	projective := bls.HashG2WithDomain(msg, domain)
+	return bls.CompressG2(projective.ToAffine())
+}
+
+// HashG2WithDomainUncompressed returns the uncompressed hash.
+func HashG2WithDomainUncompressed(msg [32]byte, domain uint64) [192]byte {
+	projective := bls.HashG2WithDomain(msg, domain)
+	return projective.ToAffine().SerializeBytes()
+}
+
 // Domain returns the bls domain given by the domain type and the operation 4 byte fork version.
 //
 // Spec pseudocode definition:
diff --git a/shared/bls/bls_test.go b/shared/bls/bls_test.go
index ce5fb1e4c0..08185f3022 100644
--- a/shared/bls/bls_test.go
+++ b/shared/bls/bls_test.go
@@ -5,6 +5,7 @@ import (
 	"crypto/rand"
 	"testing"
 
+	bls2 "github.com/phoreproject/bls"
 	"github.com/prysmaticlabs/prysm/shared/bls"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"
 )
@@ -51,3 +52,20 @@ func TestVerifyAggregate(t *testing.T) {
 		t.Error("Signature did not verify")
 	}
 }
+
+func TestHashG2WithDomain(t *testing.T) {
+	var msg [32]byte
+	copy(msg[:], []byte{'H', 'E', 'L', 'L', 'O'})
+	domain := uint64(10)
+	compHash := bls.HashG2WithDomainCompressed(msg, domain)
+	unCompHash := bls.HashG2WithDomainUncompressed(msg, domain)
+	g2Affine, err := bls2.DecompressG2(compHash)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if unCompHash != g2Affine.SerializeBytes() {
+		t.Errorf("Uncompressed and Compressed Hash do not point to the same affine point. Expected %#x but got %#x",
+			unCompHash, g2Affine.SerializeBytes())
+	}
+}