diff --git a/encrypt.cpp b/encrypt.cpp
index 5ad9f6e..54b8d93 100755
--- a/encrypt.cpp
+++ b/encrypt.cpp
@@ -209,8 +209,11 @@ int de_padding(const char *data ,int &data_len,int padding_num)
 int cipher_aes128cbc_encrypt(const char *data,char *output,int &len,char * key)
 {
 	static int first_time=1;
-	if(first_time==0) key=0;
-	else first_time=0;
+	if(aes_key_optimize)
+	{
+		if(first_time==0) key=0;
+		else first_time=0;
+	}
 
 	char buf[buf_len];
 	memcpy(buf,data,len);//TODO inefficient code
@@ -258,9 +261,11 @@ int cipher_none_encrypt(const char *data,char *output,int &len,char * key)
 int cipher_aes128cbc_decrypt(const char *data,char *output,int &len,char * key)
 {
 	static int first_time=1;
-	if(first_time==0) key=0;
-	else first_time=0;
-
+	if(aes_key_optimize)
+	{
+		if(first_time==0) key=0;
+		else first_time=0;
+	}
 	if(len%16 !=0) {mylog(log_debug,"len%%16!=0\n");return -1;}
 	//if(len<0) {mylog(log_debug,"len <0\n");return -1;}
 	AES_CBC_decrypt_buffer((unsigned char *)output,(unsigned char *)data,len,(unsigned char *)key,(unsigned char *)zero_iv);
diff --git a/encrypt.h b/encrypt.h
index b247b53..2e3b9fb 100755
--- a/encrypt.h
+++ b/encrypt.h
@@ -10,6 +10,10 @@
 
 //using namespace std;
 
+
+const int aes_key_optimize=1; //if enabled,once you used a key for aes,you cant change it anymore
+
+
 int my_encrypt(const char *data,char *output,int &len,char * key);
 int my_decrypt(const char *data,char *output,int &len,char * key);
 
@@ -35,7 +39,7 @@ extern unordered_map<int, const char *> cipher_mode_tostring;
 
 
 
-int cipher_decrypt(const char *data,char *output,int &len,char * key);
-int cipher_encrypt(const char *data,char *output,int &len,char * key);
+int cipher_decrypt(const char *data,char *output,int &len,char * key);//internal interface ,exposed for test only
+int cipher_encrypt(const char *data,char *output,int &len,char * key);//internal interface ,exposed for test only
 
 #endif
diff --git a/lib/aes_faster_c/aes.h b/lib/aes_faster_c/aes.h
index 0cb6cce..97026e2 100644
--- a/lib/aes_faster_c/aes.h
+++ b/lib/aes_faster_c/aes.h
@@ -37,7 +37,7 @@
 ////////modification begin
 #define POLARSSL_AES_ROM_TABLES
 #define POLARSSL_CIPHER_MODE_CBC
-#define POLARSSL_SELF_TEST
+//#define POLARSSL_SELF_TEST
 #define polarssl_printf printf
 ///////add end