core: include a dummy encrypted payment id when no payment is used

For better transaction uniformity, even though this wastes space.

src/cryptonote_core/cryptonote_tx_utils.cpp

@@ -223,13 +223,15 @@ namespace cryptonote
     std::vector<tx_extra_field> tx_extra_fields;
     if (parse_tx_extra(tx.extra, tx_extra_fields))
     {
+      bool add_dummy_payment_id = true;
       tx_extra_nonce extra_nonce;
       if (find_tx_extra_field_by_type(tx_extra_fields, extra_nonce))
       {
-        crypto::hash8 payment_id = null_hash8;
-        if (get_encrypted_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id))
+        crypto::hash payment_id = null_hash;
+        crypto::hash8 payment_id8 = null_hash8;
+        if (get_encrypted_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id8))
         {
-          LOG_PRINT_L2("Encrypting payment id " << payment_id);
+          LOG_PRINT_L2("Encrypting payment id " << payment_id8);
           crypto::public_key view_key_pub = get_destination_view_key_pub(destinations, change_addr);
           if (view_key_pub == null_pkey)
           {
@@ -237,21 +239,53 @@ namespace cryptonote
             return false;
           }
 
-          if (!hwdev.encrypt_payment_id(payment_id, view_key_pub, tx_key))
+          if (!hwdev.encrypt_payment_id(payment_id8, view_key_pub, tx_key))
           {
             LOG_ERROR("Failed to encrypt payment id");
             return false;
           }
 
           std::string extra_nonce;
-          set_encrypted_payment_id_to_tx_extra_nonce(extra_nonce, payment_id);
+          set_encrypted_payment_id_to_tx_extra_nonce(extra_nonce, payment_id8);
           remove_field_from_tx_extra(tx.extra, typeid(tx_extra_nonce));
           if (!add_extra_nonce_to_tx_extra(tx.extra, extra_nonce))
           {
             LOG_ERROR("Failed to add encrypted payment id to tx extra");
             return false;
           }
-          LOG_PRINT_L1("Encrypted payment ID: " << payment_id);
+          LOG_PRINT_L1("Encrypted payment ID: " << payment_id8);
+          add_dummy_payment_id = false;
+        }
+        else if (get_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id))
+        {
+          add_dummy_payment_id = false;
+        }
+      }
+
+      // we don't add one if we've got more than the usual 1 destination plus change
+      if (destinations.size() > 2)
+        add_dummy_payment_id = false;
+
+      if (add_dummy_payment_id)
+      {
+        // if we have neither long nor short payment id, add a dummy short one,
+        // this should end up being the vast majority of txes as time goes on
+        std::string extra_nonce;
+        crypto::hash8 payment_id8 = null_hash8;
+        crypto::public_key view_key_pub = get_destination_view_key_pub(destinations, change_addr);
+        if (view_key_pub == null_pkey)
+        {
+          LOG_ERROR("Failed to get key to encrypt dummy payment id with");
+        }
+        else
+        {
+          hwdev.encrypt_payment_id(payment_id8, view_key_pub, tx_key);
+          set_encrypted_payment_id_to_tx_extra_nonce(extra_nonce, payment_id8);
+          if (!add_extra_nonce_to_tx_extra(tx.extra, extra_nonce))
+          {
+            LOG_ERROR("Failed to add dummy encrypted payment id to tx extra");
+            // continue anyway
+          }
         }
       }
     }

src/simplewallet/simplewallet.cpp

@@ -4187,12 +4187,8 @@ void simple_wallet::on_money_received(uint64_t height, const crypto::hash &txid,
     tx_extra_nonce extra_nonce;
     if (find_tx_extra_field_by_type(tx_extra_fields, extra_nonce))
     {
-      crypto::hash8 payment_id8 = crypto::null_hash8;
       crypto::hash payment_id = crypto::null_hash;
-      if (get_encrypted_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id8))
-        message_writer() <<
-          tr("NOTE: this transaction uses an encrypted payment ID: consider using subaddresses instead");
-      else if (get_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id))
+      if (get_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id))
         message_writer(console_color_red, false) <<
           (m_long_payment_id_support ? tr("WARNING: this transaction uses an unencrypted payment ID: consider using subaddresses instead.") : tr("WARNING: this transaction uses an unencrypted payment ID: these are obsolete. Support will be withdrawn in the future. Use subaddresses instead."));
    }
@@ -5879,14 +5875,28 @@ bool simple_wallet::accept_loaded_tx(const std::function<size_t()> get_num_txes,
         {
           if (!payment_id_string.empty())
             payment_id_string += ", ";
-          payment_id_string = std::string("encrypted payment ID ") + epee::string_tools::pod_to_hex(payment_id8);
-          has_encrypted_payment_id = true;
+
+          // if none of the addresses are integrated addresses, it's a dummy one
+          bool is_dummy = true;
+          for (const auto &e: cd.dests)
+            if (e.is_integrated)
+              is_dummy = false;
+
+          if (is_dummy)
+          {
+            payment_id_string += std::string("dummy encrypted payment ID");
+          }
+          else
+          {
+            payment_id_string += std::string("encrypted payment ID ") + epee::string_tools::pod_to_hex(payment_id8);
+            has_encrypted_payment_id = true;
+          }
         }
         else if (get_payment_id_from_tx_extra_nonce(extra_nonce.nonce, payment_id))
         {
           if (!payment_id_string.empty())
             payment_id_string += ", ";
-          payment_id_string = std::string("unencrypted payment ID ") + epee::string_tools::pod_to_hex(payment_id);
+          payment_id_string += std::string("unencrypted payment ID ") + epee::string_tools::pod_to_hex(payment_id);
           payment_id_string += " (OBSOLETE)";
         }
       }