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/*

This is an implementation of the AES algorithm, specifically ECB, CTR and CBC mode.
Block size can be chosen in aes.h - available choices are AES128, AES192, AES256.

The implementation is verified against the test vectors in:
  National Institute of Standards and Technology Special Publication 800-38A 2001 ED

ECB-AES128
----------

  plain-text:
    6bc1bee22e409f96e93d7e117393172a
    ae2d8a571e03ac9c9eb76fac45af8e51
    30c81c46a35ce411e5fbc1191a0a52ef
    f69f2445df4f9b17ad2b417be66c3710

  key:
    2b7e151628aed2a6abf7158809cf4f3c

  resulting cipher
    3ad77bb40d7a3660a89ecaf32466ef97 
    f5d3d58503b9699de785895a96fdbaaf 
    43b1cd7f598ece23881b00e3ed030688 
    7b0c785e27e8ad3f8223207104725dd4 


NOTE:   String length must be evenly divisible by 16byte (str_len % 16 == 0)
        You should pad the end of the string with zeros if this is not the case.
        For AES192/256 the key size is proportionally larger.

*/


/*****************************************************************************/
/* Includes:                                                                 */
/*****************************************************************************/
#include <stdint.h>
#include <string.h> // CBC mode, for memset
#include "aes.h"

/*****************************************************************************/
/* Defines:                                                                  */
/*****************************************************************************/
// The number of columns comprising a state in AES. This is a constant in AES. Value=4
#define Nb 4

#if defined(AES256) && (AES256 == 1)
    #define Nk 8
    #define Nr 14
#elif defined(AES192) && (AES192 == 1)
    #define Nk 6
    #define Nr 12
#else
    #define Nk 4        // The number of 32 bit words in a key.
    #define Nr 10       // The number of rounds in AES Cipher.
#endif

// jcallan@github points out that declaring Multiply as a function 
// reduces code size considerably with the Keil ARM compiler.
// See this link for more information: https://github.com/kokke/tiny-AES-C/pull/3
#ifndef MULTIPLY_AS_A_FUNCTION
  #define MULTIPLY_AS_A_FUNCTION 0
#endif