Do memwipe for critical secret keys copied to rct::key

src/wallet/wallet2.cpp

@@ -3217,6 +3217,7 @@ void wallet2::generate(const std::string& wallet_, const epee::wipeable_string&
   for (const auto &msk: multisig_keys)
     sc_add(skey.bytes, skey.bytes, rct::sk2rct(msk).bytes);
   THROW_WALLET_EXCEPTION_IF(!(rct::rct2sk(skey) == spend_secret_key), error::invalid_multisig_seed);
+  memwipe(&skey, sizeof(rct::key));
 
   m_account.make_multisig(view_secret_key, spend_secret_key, spend_public_key, multisig_keys);
   m_account.finalize_multisig(spend_public_key);
@@ -3563,6 +3564,7 @@ std::string wallet2::make_multisig(const epee::wipeable_string &password,
   MINFO("Creating multisig address...");
   CHECK_AND_ASSERT_THROW_MES(m_account.make_multisig(view_skey, rct::rct2sk(spend_skey), rct::rct2pk(spend_pkey), multisig_keys),
       "Failed to create multisig wallet due to bad keys");
+  memwipe(&spend_skey, sizeof(rct::key));
 
   m_account_public_address = m_account.get_keys().m_account_address;
   m_watch_only = false;