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### Tiny AES128 in C
This is a small and portable implementation of the AES128 ECB encryption algorithm implemented in C.
The API is very simple and looks like this (I am using C99 `<stdint.h>`-style annotated types):
```C
void AES128_ECB_encrypt(uint8_t* input, uint8_t* key, uint8_t *output);
void AES128_ECB_decrypt(uint8_t* input, uint8_t* key, uint8_t *output);
```
The module uses just a bit more than 200 bytes of RAM and 2.5K ROM when compiled for ARM (~2K for Thumb but 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
$ size aes.o
text data bss dec hex filename
2515 0 204 2719 a9f aes.o
.. and when compiling for the THUMB instruction set, we end up around 2K in code size.
$ arm-none-eabi-gcc -mthumb -Os -c aes.c
$ size aes.o
text data bss dec hex filename
1883 0 204 2087 827 aes.o
I am using Mentor Graphics free 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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