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### Tiny AES128 in C
This is a small and portable implementation of the AES128 algorithm implemented in C.
The module uses just a bit more than 200 bytes of RAM and 1K ROM when compiled for ARM (YMMV).
It is the smallest implementation in C I've seen yet, but do contact me if you know of something smaller (or have improvements to the code here).
I've successfully used the code on 64bit x86, 32bit ARM and 8 bit AVR platforms.
GCC size output when compiled for ARM:
$ arm-none-eabi-gcc -Os -c aes.c -o aes.o
$ size aes.o
text data bss dec hex filename
1079 0 204 1283 503 aes.o
$ arm-none-eabi-gcc -O2 -c aes.c -o aes.o
$ size aes.o
text data bss dec hex filename
1024 0 204 1228 4cc aes.o
And if we're compiling for the Thumb ISA:
$ arm-none-eabi-gcc -O2 -c -mthumb aes.c -o aes.o
$ size aes.o
text data bss dec hex filename
856 0 204 1060 424 aes.o
$ arm-none-eabi-gcc -Os -c -mthumb aes.c -o aes.o
$ size aes.o
text data bss dec hex filename
867 0 204 1071 42f aes.o
Somehow, -O2 is a bit smaller than -Os with this compiler. I am using Mentor Graphics ARM toolchain:
$ arm-none-eabi-gcc --version
arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors) 4.8.3 20131129 (release) [ARM/embedded-4_8-branch revision 205641]
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
The implementation is verified against the data in:
[National Institute of Standards and Technology Special Publication 800-38A 2001 ED](http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf) Appendix F: Example Vectors for Modes of Operation of the AES.
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