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Dec 25, 2014

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, 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.
  • 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.

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