From bb30628de1b1eb7f208e143488b61a1980224050 Mon Sep 17 00:00:00 2001
From: Alexander Block <ablock84@gmail.com>
Date: Thu, 1 Nov 2018 17:18:24 +0100
Subject: [PATCH] Implement DHKeyExchange (#43)

* Implement DHKeyExchange

* Call CheckRelicErrors in DHKeyExchange
---
 src/bls.cpp        | 10 ++++++++++
 src/bls.hpp        |  2 ++
 src/privatekey.hpp |  1 +
 src/publickey.hpp  |  1 +
 4 files changed, 14 insertions(+)

diff --git a/src/bls.cpp b/src/bls.cpp
index d2375baf015ff0..2ec05ae2e4e21b 100644
--- a/src/bls.cpp
+++ b/src/bls.cpp
@@ -111,6 +111,16 @@ void BLS::HashPubKeys(bn_t* output, size_t numOutputs,
     CheckRelicErrors();
 }
 
+PublicKey BLS::DHKeyExchange(const PrivateKey& privKey, const PublicKey& pubKey) {
+    AssertInitialized();
+    if (!privKey.keydata) {
+        throw std::string("keydata not initialized");
+    }
+    PublicKey ret = pubKey.Exp(*privKey.keydata);
+    CheckRelicErrors();
+    return ret;
+}
+
 void BLS::CheckRelicErrors() {
     if (!core_get()) {
         throw std::string("Library not initialized properly. Call BLS::Init()");
diff --git a/src/bls.hpp b/src/bls.hpp
index d100eeee90e385..a58cbf2f1dea65 100644
--- a/src/bls.hpp
+++ b/src/bls.hpp
@@ -63,6 +63,8 @@ class BLS {
             std::vector<uint8_t*> const &serPubKeys,
             std::vector<size_t> const &sortedIndices);
 
+    static PublicKey DHKeyExchange(const PrivateKey& privKey, const PublicKey& pubKey);
+
     static void CheckRelicErrors();
 };
 } // end namespace bls
diff --git a/src/privatekey.hpp b/src/privatekey.hpp
index 7ecb09f6a37def..91133eb2e884f0 100644
--- a/src/privatekey.hpp
+++ b/src/privatekey.hpp
@@ -25,6 +25,7 @@
 #include "signature.hpp"
 namespace bls {
 class PrivateKey {
+ friend class BLS;
  public:
     // Private keys are represented as 32 byte field elements. Note that
     // not all 32 byte integers are valid keys, the private key must be
diff --git a/src/publickey.hpp b/src/publickey.hpp
index 5b77605051f5e5..8909294775c853 100644
--- a/src/publickey.hpp
+++ b/src/publickey.hpp
@@ -31,6 +31,7 @@ class PublicKey {
  friend class InsecureSignature;
  friend class Signature;
  friend class ExtendedPublicKey;
+ friend class BLS;
  public:
     static const size_t PUBLIC_KEY_SIZE = 48;