diff --git a/armsrc/optimized_cipher.c b/armsrc/optimized_cipher.c
index 31a47a33f..98c2034e2 100644
--- a/armsrc/optimized_cipher.c
+++ b/armsrc/optimized_cipher.c
@@ -267,14 +267,18 @@ void opt_doReaderMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4]) {
     memcpy(mac, dest, 4);
 }
 
+void opt_doReaderMAC_2(State _init,  uint8_t *nr, uint8_t mac[4], const uint8_t *div_key_p) {
+    opt_suc(div_key_p, &_init, nr, 4, false);
+    opt_output(div_key_p, &_init, mac);
+}
+
+
 void doMAC_N(uint8_t *in_p, uint8_t in_size, uint8_t *div_key_p, uint8_t mac[4]) {
     uint8_t dest [] = {0, 0, 0, 0, 0, 0, 0, 0};
     opt_MAC_N(div_key_p, in_p, in_size, dest);
     memcpy(mac, dest, 4);
 }
 
-
-
 void opt_doTagMAC(uint8_t *cc_p, const uint8_t *div_key_p, uint8_t mac[4]) {
     State _init  =  {
         ((div_key_p[0] ^ 0x4c) + 0xEC) & 0xFF,// l
diff --git a/armsrc/optimized_cipher.h b/armsrc/optimized_cipher.h
index 6aa97352d..587f6b7a6 100644
--- a/armsrc/optimized_cipher.h
+++ b/armsrc/optimized_cipher.h
@@ -21,6 +21,9 @@ typedef struct {
 /** The reader MAC is MAC(key, CC * NR )
  **/
 void opt_doReaderMAC(uint8_t *cc_nr_p, uint8_t *div_key_p, uint8_t mac[4]);
+
+void opt_doReaderMAC_2(State _init,  uint8_t *nr, uint8_t mac[4], const uint8_t *div_key_p);
+
 /**
  * The tag MAC is MAC(key, CC * NR * 32x0))
  */