rct: avoid the need for the last II element

This element is used in the generation of the MLSAG, but isn't
needed in verification.
Also misc changes in the cryptonote code to match, by mooo.

2 files changed, 9 insertions, 18 deletions

diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index f6f56b086..91a9d5d6f 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -2475,12 +2475,12 @@ bool Blockchain::check_tx_inputs(const transaction& tx, tx_verification_context
       const rct::ctkeyM &mixRing = tx.rct_signatures.mixRing.empty() ? reconstructed_mixRing : tx.rct_signatures.mixRing;
       // always do II, because it's split in the simple version, and always do outPk
 
-      // all MGs should have the same II size (1)
+      // all MGs should have empty II
       for (size_t n = 0; n < tx.rct_signatures.MGs.size(); ++n)
       {
-        if (tx.rct_signatures.MGs[n].II.size() != 1)
+        if (tx.rct_signatures.MGs[n].II.size() != 0)
         {
-          LOG_PRINT_L1("Failed to check ringct signatures: mismatched MGs II sizes");
+          LOG_PRINT_L1("Failed to check ringct signatures: non empty MGs II");
           return false;
         }
       }
@@ -2489,7 +2489,6 @@ bool Blockchain::check_tx_inputs(const transaction& tx, tx_verification_context
       for (size_t n = 0; n < tx.vin.size(); ++n)
       {
         reconstructed_II[n].push_back(rct::ki2rct(boost::get<txin_to_key>(tx.vin[n]).k_image));
-        reconstructed_II[n].push_back(tx.rct_signatures.MGs[n].II[0]);
       }
 
       if (tx.rct_signatures.outPk.size() != tx.vout.size())
@@ -2579,7 +2578,7 @@ bool Blockchain::check_tx_inputs(const transaction& tx, tx_verification_context
       // if the tx already has a non empty mixRing and/or II, use them,
       // else reconstruct them. Always do outPk.
       const rct::ctkeyM &mixRing = tx.rct_signatures.mixRing.empty() ? reconstructed_mixRing : tx.rct_signatures.mixRing;
-      const rct::keyV &II = tx.rct_signatures.MG.II.size() == 1 ? reconstructed_II : tx.rct_signatures.MG.II;
+      const rct::keyV &II = tx.rct_signatures.MG.II.empty() ? reconstructed_II : tx.rct_signatures.MG.II;
       const rct::ctkeyV outPk = reconstructed_outPk;
 
       // RCT needs the same mixin for all inputs
@@ -2604,14 +2603,13 @@ bool Blockchain::check_tx_inputs(const transaction& tx, tx_verification_context
         }
       }
 
-      if (tx.rct_signatures.MG.II.size() == 1)
+      if (tx.rct_signatures.MG.II.empty())
       {
         reconstructed_II.resize(tx.vin.size());
         for (size_t n = 0; n < tx.vin.size(); ++n)
         {
           reconstructed_II[n] = rct::ki2rct(boost::get<txin_to_key>(tx.vin[n]).k_image);
         }
-        reconstructed_II.push_back(tx.rct_signatures.MG.II.back());
       }
 
       if (tx.rct_signatures.outPk.size() != tx.vout.size())
@@ -2657,7 +2655,7 @@ bool Blockchain::check_tx_inputs(const transaction& tx, tx_verification_context
         }
       }
 
-      if (II.size() != 1 + tx.vin.size())
+      if (II.size() != tx.vin.size())
       {
         LOG_PRINT_L1("Failed to check ringct signatures: mismatched II/vin sizes");
         return false;
diff --git a/src/cryptonote_core/cryptonote_boost_serialization.h b/src/cryptonote_core/cryptonote_boost_serialization.h
index 41f864803..8a82aa7a7 100644
--- a/src/cryptonote_core/cryptonote_boost_serialization.h
+++ b/src/cryptonote_core/cryptonote_boost_serialization.h
@@ -209,19 +209,12 @@ namespace boost
     a & x.s;
   }
 
-  inline void serialize(boost::archive::binary_iarchive &a, rct::mgSig &x, const boost::serialization::version_type ver)
-  {
-    a & x.ss;
-    a & x.cc;
-    x.II.resize(1);
-    a & x.II[0];
-  }
-
-  inline void serialize(boost::archive::binary_oarchive &a, rct::mgSig &x, const boost::serialization::version_type ver)
+  template <class Archive>
+  inline void serialize(Archive &a, rct::mgSig &x, const boost::serialization::version_type ver)
   {
     a & x.ss;
     a & x.cc;
-    a & x.II.back();
+    // a & x.II; // not serialized, we can recover it from the tx vin
   }
 
   template <class Archive>