From 5db5e42ec325d45f40a5f91fd8e454a9714ad0ba Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@z.cash>
Date: Wed, 24 Aug 2016 15:49:38 +1200
Subject: [PATCH] Add optional bool to disable computation of proof in
 JSDescription constructor

---
 src/primitives/transaction.cpp | 10 +++++++---
 src/primitives/transaction.h   |  3 ++-
 src/zcash/JoinSplit.cpp        |  9 +++++++--
 src/zcash/JoinSplit.hpp        |  3 ++-
 4 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/src/primitives/transaction.cpp b/src/primitives/transaction.cpp
index 854a0be66..5c1f94758 100644
--- a/src/primitives/transaction.cpp
+++ b/src/primitives/transaction.cpp
@@ -15,11 +15,14 @@ JSDescription::JSDescription(ZCJoinSplit& params,
             const boost::array<libzcash::JSInput, ZC_NUM_JS_INPUTS>& inputs,
             const boost::array<libzcash::JSOutput, ZC_NUM_JS_OUTPUTS>& outputs,
             CAmount vpub_old,
-            CAmount vpub_new) : vpub_old(vpub_old), vpub_new(vpub_new), anchor(anchor)
+            CAmount vpub_new,
+            bool computeProof) : vpub_old(vpub_old), vpub_new(vpub_new), anchor(anchor)
 {
     boost::array<libzcash::Note, ZC_NUM_JS_OUTPUTS> notes;
 
-    params.loadProvingKey();
+    if (computeProof) {
+        params.loadProvingKey();
+    }
     proof = params.prove(
         inputs,
         outputs,
@@ -33,7 +36,8 @@ JSDescription::JSDescription(ZCJoinSplit& params,
         commitments,
         vpub_old,
         vpub_new,
-        anchor
+        anchor,
+        computeProof
     );
 }
 
diff --git a/src/primitives/transaction.h b/src/primitives/transaction.h
index c88b26d17..44375fc63 100644
--- a/src/primitives/transaction.h
+++ b/src/primitives/transaction.h
@@ -74,7 +74,8 @@ public:
             const boost::array<libzcash::JSInput, ZC_NUM_JS_INPUTS>& inputs,
             const boost::array<libzcash::JSOutput, ZC_NUM_JS_OUTPUTS>& outputs,
             CAmount vpub_old,
-            CAmount vpub_new
+            CAmount vpub_new,
+            bool computeProof = true // Set to false in some tests
     );
 
     // Verifies that the JoinSplit proof is correct.
diff --git a/src/zcash/JoinSplit.cpp b/src/zcash/JoinSplit.cpp
index b103581b3..71c1ae0ad 100644
--- a/src/zcash/JoinSplit.cpp
+++ b/src/zcash/JoinSplit.cpp
@@ -173,9 +173,10 @@ public:
         boost::array<uint256, NumOutputs>& out_commitments,
         uint64_t vpub_old,
         uint64_t vpub_new,
-        const uint256& rt
+        const uint256& rt,
+        bool computeProof
     ) {
-        if (!pk) {
+        if (computeProof && !pk) {
             throw std::runtime_error("JoinSplit proving key not loaded");
         }
 
@@ -231,6 +232,10 @@ public:
             out_macs[i] = PRF_pk(inputs[i].key, i, h_sig);
         }
 
+        if (!computeProof) {
+            return ZCProof();
+        }
+
         protoboard<FieldT> pb;
         {
             joinsplit_gadget<FieldT, NumInputs, NumOutputs> g(pb);
diff --git a/src/zcash/JoinSplit.hpp b/src/zcash/JoinSplit.hpp
index e9e89c62d..1b655728d 100644
--- a/src/zcash/JoinSplit.hpp
+++ b/src/zcash/JoinSplit.hpp
@@ -73,7 +73,8 @@ public:
         boost::array<uint256, NumOutputs>& out_commitments,
         uint64_t vpub_old,
         uint64_t vpub_new,
-        const uint256& rt
+        const uint256& rt,
+        bool computeProof = true
     ) = 0;
 
     virtual bool verify(