efm32 an0060 encrypt aes128 support

In AN0060, there is a encrypt.exe which support AES256 only. But for ZG device supports AES128, we need to make a change and generate new exe file. The steps as follows:

• Download libtom source code
  Goto https://github.com/libtom/libtomcrypt, get latest version 1.17.
• Extract it and generate directory “libtomcrypt-1.17”
• Run msys under windows.
  Here we use the msys from Railsinstaller directory

$ C:\RailsInstaller\DevKit\msys.bat

• In msys window, enter libtomcrypt-1.17, edit makefile.
  Uncomment line 12 and 13, save and close it.

CC=gcc
LD=ld

• Generate libtomcrypt.a file

$ make

The generated lib file in “libtomcrypt-1.17” directory.

• Copy AN0060 encrypt.c into “libtomcrypt-1.17” directory.
  The file can be found in C:\SiliconLabs\SimplicityStudio\v2\developer\sdks\efm32\v2\an\an0060_efm32_aes_bootloader\src\encrypt\encrypt.c
• Modify encrypt.c to support AES128, save and close it.
  On line 51 change the AES_KEY_SIZE from 32 to 16

-#define AES_KEY_SIZE 32
+#define AES_KEY_SIZE 16

• Generate encrypt.exe

$ gcc -o encrypt encrypt.c -I./src/headers  -L./ -ltomcrypt

The generated encrypt.exe in “libtomcrypt-1.17” directory.

http://markding.github.io/2014/12/25/efm32-an0060-encrypt-aes128-support.html