diff --git a/build/libraries/aes/ARM7/aes_util.c b/build/libraries/aes/ARM7/aes_util.c
new file mode 100644
index 00000000..47e82986
--- /dev/null
+++ b/build/libraries/aes/ARM7/aes_util.c
@@ -0,0 +1,46 @@
+/*---------------------------------------------------------------------------*
+  Project:  TwlIPL - libraries - aes
+  File:     aes_util.c
+
+  Copyright 2007 Nintendo.  All rights reserved.
+
+  These coded instructions, statements, and computer programs contain
+  proprietary information of Nintendo of America Inc. and/or Nintendo
+  Company Ltd., and are protected by Federal copyright law.  They may
+  not be disclosed to third parties or copied or duplicated in any form,
+  in whole or in part, without the prior written consent of Nintendo.
+
+  $Date::            $
+  $Rev$
+  $Author$
+ *---------------------------------------------------------------------------*/
+
+#include <firm/aes.h>
+
+/*---------------------------------------------------------------------------*
+  Name:         AESi_AddCounter
+
+  Description:  calculate updated counter
+
+  Arguments:    pCounter    pointer to the counter at offset 0
+                nums        offset in blocks (AES_BLOCK_SIZE)
+
+  Returns:      None
+ *---------------------------------------------------------------------------*/
+void AESi_AddCounter(AESCounter* pCounter, u32 nums)
+{
+    u32 data = 0;
+    int i;
+    for (i = 0; i < 16; i++)
+    {
+        data += pCounter->bytes[i] + (nums & 0xFF);
+        pCounter->bytes[i] = (u8)(data & 0xFF);
+        data >>= 8;
+        nums >>= 8;
+        if ( !data && !nums )
+        {
+            break;
+        }
+    }
+}
+