diff --git a/app/crypto/aes.c b/app/crypto/aes.c
index b9e5a81..4bd068d 100644
--- a/app/crypto/aes.c
+++ b/app/crypto/aes.c
@@ -1,10 +1,7 @@
 #include <string.h>
 #include "aes.h"
 #include "hal.h"
-
-const static uint8_t cmac_iv[AES_IV_SIZE] __attribute__((aligned(4))) = {
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
-};
+#include "mem.h"
 
 #ifdef SOFT_AES
 #define AES_128_KEYROUND 10
@@ -125,7 +122,7 @@ uint8_t aes_decrypt_cbc(const uint8_t* key, const uint8_t* iv, const uint8_t* da
 }
 
 uint8_t aes_cmac(const uint8_t* key, const uint8_t* data, uint32_t len, uint8_t* out) {
-  hal_aes256_init(AES_ENCRYPT, AES_CBC, key, cmac_iv);
+  hal_aes256_init(AES_ENCRYPT, AES_CBC, key, ZERO32);
 
   for(uint32_t i = 0; i < len; i += AES_BLOCK_SIZE) {
     hal_aes256_block_process(&data[i], out);
diff --git a/app/mem.c b/app/mem.c
index a62ae41..b60e6df 100644
--- a/app/mem.c
+++ b/app/mem.c
@@ -5,3 +5,8 @@ APP_ALIGNED(uint8_t g_mem_heap[MEM_HEAP_SIZE], 4);
 APP_ALIGNED(uint8_t g_flash_swap[HAL_FLASH_BLOCK_SIZE], 4);
 
 APP_SECTION(uint32_t g_bootcmd, ".bootcmd,\"aw\",%nobits@");
+
+const uint8_t ZERO32[32] __attribute__((aligned(4))) = {
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+};
diff --git a/app/mem.h b/app/mem.h
index 81e0cd0..52180dd 100644
--- a/app/mem.h
+++ b/app/mem.h
@@ -8,6 +8,8 @@
 
 #define BOOTCMD_SWITCH_FW 0x83578007
 
+extern const uint8_t ZERO32[32];
+
 extern uint8_t g_mem_heap[MEM_HEAP_SIZE];
 extern uint8_t g_flash_swap[HAL_FLASH_BLOCK_SIZE];
 extern uint8_t g_camera_fb[CAMERA_FB_COUNT][CAMERA_FB_SIZE];