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 /*
 
 This is an implementation of the EXAES algorithm, specifically ECB and CBC mode.
 Block size can be chosen in exaes.h - available choices are EXAES128, EXAES192, EXAES256.
 
 The implementation is verified against the test vectors in:
   National Institute of Standards and Technology Special Publication 800-38A 2001 ED
 
 ECB-EXAES128
 ----------
 
   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 EXAES192/256 the key size is proportionally larger.
 
 */
 
 
 /*****************************************************************************/
 /* Includes:                                                                 */
 /*****************************************************************************/
 #include <stdint.h>
 #include <string.h> // CBC mode, for memset
 #include "exaes.h"
 
 /*****************************************************************************/
 /* Defines:                                                                  */
 /*****************************************************************************/
 // The number of columns comprising a state in EXAES. This is a constant in EXAES. Value=4
 #define Nb 4
 #define BLOCKLEN 16 //Block length in bytes EXAES is 128b block only
 
 #if defined(EXAES256) && (EXAES256 == 1)
     #define Nk 8
     #define KEYLEN 32
     #define Nr 14
     #define keyExpSize 240
 #elif defined(EXAES192) && (EXAES192 == 1)
     #define Nk 6
     #define KEYLEN 24
     #define Nr 12
     #define keyExpSize 208
 #else
     #define Nk 4        // The number of 32 bit words in a key.
     #define KEYLEN 16   // Key length in bytes
     #define Nr 10       // The number of rounds in EXAES Cipher.
     #define keyExpSize 176
 #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-EXAES128-C/pull/3
 #ifndef MULTIPLY_AS_A_FUNCTION
   #define MULTIPLY_AS_A_FUNCTION 0
 #endif
 
 
 /*****************************************************************************/
 /* Private variables:                                                        */
 /*****************************************************************************/
 // state - array holding the intermediate results during decryption.
 typedef uint8_t state_t[4][4];
 static __thread state_t* state;
 
 // The array that stores the round keys.
 static __thread uint8_t RoundKey[keyExpSize];
 
 // The Key input to the EXAES Program
 static __thread const uint8_t* Key;
 
 #if defined(CBC) && CBC
   // Initial Vector used only for CBC mode
   static __thread uint8_t* Iv;
 #endif
 
 // The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
 // The numbers below can be computed dynamically trading ROM for RAM - 
 // This can be useful in (embedded) bootloader applications, where ROM is often limited.
 static const uint8_t sbox[256] = {
   //0     1    2      3     4    5     6     7      8    9     A      B    C     D     E     F
   0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
   0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
   0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
   0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
   0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
   0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
   0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
   0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
   0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
   0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
   0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
   0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
   0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
   0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
   0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
   0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 };
 
 static const uint8_t rsbox[256] = {
   0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
   0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
   0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
   0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
   0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
   0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
   0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
   0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
   0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
   0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
   0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
   0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
   0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
   0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
   0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
   0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d };
 
 // The round constant word array, Rcon[i], contains the values given by 
 // x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
 static const uint8_t Rcon[11] = {
   0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 };
 
 /*
  * Jordan Goulder points out in PR #12 (https://github.com/kokke/tiny-EXAES128-C/pull/12),
  * that you can remove most of the elements in the Rcon array, because they are unused.
  *
  * From Wikipedia's article on the Rijndael key schedule @ https://en.wikipedia.org/wiki/Rijndael_key_schedule#Rcon
  * 
  * "Only the first some of these constants are actually used – up to rcon[10] for EXAES-128 (as 11 round keys are needed), 
  *  up to rcon[8] for EXAES-192, up to rcon[7] for EXAES-256. rcon[0] is not used in EXAES algorithm."
  *
  * ... which is why the full array below has been 'disabled' below.
  */
 #if 0
 static const uint8_t Rcon[256] = {
   0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
   0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39,
   0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a,
   0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
   0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef,
   0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc,
   0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b,
   0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
   0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94,
   0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20,
   0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35,
   0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f,
   0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
   0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63,
   0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd,
   0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d };
 #endif
 
 /*****************************************************************************/
 /* Private functions:                                                        */
 /*****************************************************************************/
 static uint8_t getSBoxValue(uint8_t num)
 {
   return sbox[num];
 }
 
 static uint8_t getSBoxInvert(uint8_t num)
 {
   return rsbox[num];
 }
 
 // This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states. 
 static void KeyExpansion(void)
 {
   uint32_t i, k;
   uint8_t tempa[4]; // Used for the column/row operations
   
   // The first round key is the key itself.
   for (i = 0; i < Nk; ++i)
   {
     RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
     RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
     RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
     RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
   }
 
   // All other round keys are found from the previous round keys.
   //i == Nk
   for (; i < Nb * (Nr + 1); ++i)
   {
     {
       tempa[0]=RoundKey[(i-1) * 4 + 0];
       tempa[1]=RoundKey[(i-1) * 4 + 1];
       tempa[2]=RoundKey[(i-1) * 4 + 2];
       tempa[3]=RoundKey[(i-1) * 4 + 3];
     }
 
     if (i % Nk == 0)
     {
       // This function shifts the 4 bytes in a word to the left once.
       // [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
 
       // Function RotWord()
       {
         k = tempa[0];
         tempa[0] = tempa[1];
         tempa[1] = tempa[2];
         tempa[2] = tempa[3];
         tempa[3] = k;
       }
 
       // SubWord() is a function that takes a four-byte input word and 
       // applies the S-box to each of the four bytes to produce an output word.
 
       // Function Subword()
       {
         tempa[0] = getSBoxValue(tempa[0]);
         tempa[1] = getSBoxValue(tempa[1]);
         tempa[2] = getSBoxValue(tempa[2]);
         tempa[3] = getSBoxValue(tempa[3]);
       }
 
       tempa[0] =  tempa[0] ^ Rcon[i/Nk];
     }
 #if defined(EXAES256) && (EXAES256 == 1)
     if (i % Nk == 4)
     {
       // Function Subword()
       {
         tempa[0] = getSBoxValue(tempa[0]);
         tempa[1] = getSBoxValue(tempa[1]);
         tempa[2] = getSBoxValue(tempa[2]);
         tempa[3] = getSBoxValue(tempa[3]);
       }
     }
 #endif
     RoundKey[i * 4 + 0] = RoundKey[(i - Nk) * 4 + 0] ^ tempa[0];
     RoundKey[i * 4 + 1] = RoundKey[(i - Nk) * 4 + 1] ^ tempa[1];
     RoundKey[i * 4 + 2] = RoundKey[(i - Nk) * 4 + 2] ^ tempa[2];
     RoundKey[i * 4 + 3] = RoundKey[(i - Nk) * 4 + 3] ^ tempa[3];
   }
 }
 
 // This function adds the round key to state.
 // The round key is added to the state by an XOR function.
 static void AddRoundKey(uint8_t round)
 {
   uint8_t i,j;
   for (i=0;i<4;++i)
   {
     for (j = 0; j < 4; ++j)
     {
       (*state)[i][j] ^= RoundKey[round * Nb * 4 + i * Nb + j];
     }
   }
 }
 
 // The SubBytes Function Substitutes the values in the
 // state matrix with values in an S-box.
 static void SubBytes(void)
 {
   uint8_t i, j;
   for (i = 0; i < 4; ++i)
   {
     for (j = 0; j < 4; ++j)
     {
       (*state)[j][i] = getSBoxValue((*state)[j][i]);
     }
   }
 }
 
 // The ShiftRows() function shifts the rows in the state to the left.
 // Each row is shifted with different offset.
 // Offset = Row number. So the first row is not shifted.
 static void ShiftRows(void)
 {
   uint8_t temp;
 
   // Rotate first row 1 columns to left  
   temp           = (*state)[0][1];
   (*state)[0][1] = (*state)[1][1];
   (*state)[1][1] = (*state)[2][1];
   (*state)[2][1] = (*state)[3][1];
   (*state)[3][1] = temp;
 
   // Rotate second row 2 columns to left  
   temp           = (*state)[0][2];
   (*state)[0][2] = (*state)[2][2];
   (*state)[2][2] = temp;
 
   temp           = (*state)[1][2];
   (*state)[1][2] = (*state)[3][2];
   (*state)[3][2] = temp;
 
   // Rotate third row 3 columns to left
   temp           = (*state)[0][3];
   (*state)[0][3] = (*state)[3][3];
   (*state)[3][3] = (*state)[2][3];
   (*state)[2][3] = (*state)[1][3];
   (*state)[1][3] = temp;
 }
 
 static uint8_t xtime(uint8_t x)
 {
   return ((x<<1) ^ (((x>>7) & 1) * 0x1b));
 }
 
 // MixColumns function mixes the columns of the state matrix
 static void MixColumns(void)
 {
   uint8_t i;
   uint8_t Tmp,Tm,t;
   for (i = 0; i < 4; ++i)
   {  
     t   = (*state)[i][0];
     Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3] ;
     Tm  = (*state)[i][0] ^ (*state)[i][1] ; Tm = xtime(Tm);  (*state)[i][0] ^= Tm ^ Tmp ;
     Tm  = (*state)[i][1] ^ (*state)[i][2] ; Tm = xtime(Tm);  (*state)[i][1] ^= Tm ^ Tmp ;
     Tm  = (*state)[i][2] ^ (*state)[i][3] ; Tm = xtime(Tm);  (*state)[i][2] ^= Tm ^ Tmp ;
     Tm  = (*state)[i][3] ^ t ;              Tm = xtime(Tm);  (*state)[i][3] ^= Tm ^ Tmp ;
   }
 }
 
 // Multiply is used to multiply numbers in the field GF(2^8)
 #if MULTIPLY_AS_A_FUNCTION
 static uint8_t Multiply(uint8_t x, uint8_t y)
 {
   return (((y & 1) * x) ^
        ((y>>1 & 1) * xtime(x)) ^
        ((y>>2 & 1) * xtime(xtime(x))) ^
        ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^
        ((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))));
   }
 #else
 #define Multiply(x, y)                                \
       (  ((y & 1) * x) ^                              \
       ((y>>1 & 1) * xtime(x)) ^                       \
       ((y>>2 & 1) * xtime(xtime(x))) ^                \
       ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^         \
       ((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))))   \
 
 #endif
 
 // MixColumns function mixes the columns of the state matrix.
 // The method used to multiply may be difficult to understand for the inexperienced.
 // Please use the references to gain more information.
 static void InvMixColumns(void)
 {
   int i;
   uint8_t a, b, c, d;
   for (i = 0; i < 4; ++i)
   { 
     a = (*state)[i][0];
     b = (*state)[i][1];
     c = (*state)[i][2];
     d = (*state)[i][3];
 
     (*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
     (*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
     (*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
     (*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
   }
 }
 
 
 // The SubBytes Function Substitutes the values in the
 // state matrix with values in an S-box.
 static void InvSubBytes(void)
 {
   uint8_t i,j;
   for (i = 0; i < 4; ++i)
   {
     for (j = 0; j < 4; ++j)
     {
       (*state)[j][i] = getSBoxInvert((*state)[j][i]);
     }
   }
 }
 
 static void InvShiftRows(void)
 {
   uint8_t temp;
 
   // Rotate first row 1 columns to right  
   temp = (*state)[3][1];
   (*state)[3][1] = (*state)[2][1];
   (*state)[2][1] = (*state)[1][1];
   (*state)[1][1] = (*state)[0][1];
   (*state)[0][1] = temp;
 
   // Rotate second row 2 columns to right 
   temp = (*state)[0][2];
   (*state)[0][2] = (*state)[2][2];
   (*state)[2][2] = temp;
 
   temp = (*state)[1][2];
   (*state)[1][2] = (*state)[3][2];
   (*state)[3][2] = temp;
 
   // Rotate third row 3 columns to right
   temp = (*state)[0][3];
   (*state)[0][3] = (*state)[1][3];
   (*state)[1][3] = (*state)[2][3];
   (*state)[2][3] = (*state)[3][3];
   (*state)[3][3] = temp;
 }
 
 
 // Cipher is the main function that encrypts the PlainText.
 static void Cipher(void)
 {
   uint8_t round = 0;
 
   // Add the First round key to the state before starting the rounds.
   AddRoundKey(0); 
   
   // There will be Nr rounds.
   // The first Nr-1 rounds are identical.
   // These Nr-1 rounds are executed in the loop below.
   for (round = 1; round < Nr; ++round)
   {
     SubBytes();
     ShiftRows();
     MixColumns();
     AddRoundKey(round);
   }
   
   // The last round is given below.
   // The MixColumns function is not here in the last round.
   SubBytes();
   ShiftRows();
   AddRoundKey(Nr);
 }
 
 static void InvCipher(void)
 {
   uint8_t round=0;
 
   // Add the First round key to the state before starting the rounds.
   AddRoundKey(Nr); 
 
   // There will be Nr rounds.
   // The first Nr-1 rounds are identical.
   // These Nr-1 rounds are executed in the loop below.
   for (round = (Nr - 1); round > 0; --round)
   {
     InvShiftRows();
     InvSubBytes();
     AddRoundKey(round);
     InvMixColumns();
   }
   
   // The last round is given below.
   // The MixColumns function is not here in the last round.
   InvShiftRows();
   InvSubBytes();
   AddRoundKey(0);
 }
 
 
 /*****************************************************************************/
 /* Public functions:                                                         */
 /*****************************************************************************/
 #if defined(ECB) && (ECB == 1)
 
 
 void EXAES_ECB_encrypt(const uint8_t* input, const uint8_t* key, uint8_t* output, const uint32_t length)
 {
   // Copy input to output, and work in-memory on output
   memcpy(output, input, length);
   state = (state_t*)output;
 
   Key = key;
   KeyExpansion();
 
   // The next function call encrypts the PlainText with the Key using EXAES algorithm.
   Cipher();
 }
 
 void EXAES_ECB_decrypt(const uint8_t* input, const uint8_t* key, uint8_t *output, const uint32_t length)
 {
   // Copy input to output, and work in-memory on output
   memcpy(output, input, length);
   state = (state_t*)output;
 
   // The KeyExpansion routine must be called before encryption.
   Key = key;
   KeyExpansion();
 
   InvCipher();
 }
 
 
 #endif // #if defined(ECB) && (ECB == 1)
 
 
 
 
 
 #if defined(CBC) && (CBC == 1)
 
 
 static void XorWithIv(uint8_t* buf)
 {
   uint8_t i;
   for (i = 0; i < BLOCKLEN; ++i) //WAS for(i = 0; i < KEYLEN; ++i) but the block in EXAES is always 128bit so 16 bytes!
   {
     buf[i] ^= Iv[i];
   }
 }
 
 //Warning ! This will try to read full block !!!
 //Thus input must be with exact size !!!!
 void EXAES_CBC_encrypt_buffer(uint8_t* output, uint8_t* input, uint32_t length, const uint8_t* key, const uint8_t* iv)
 {
   uintptr_t i;
   uint8_t extra = length % BLOCKLEN; /* Remaining bytes in the last non-full block */
 
   // Skip the key expansion if key is passed as 0
   if (0 != key)
   {
     Key = key;
     KeyExpansion();
   }
 
   if (iv != 0)
   {
     Iv = (uint8_t*)iv;
   }
 
 
   //Fix for the mem read overflow
   for (i = 0; i < length-extra; i += BLOCKLEN)
   {
     memcpy(output, input, BLOCKLEN);
     XorWithIv(output);
     state = (state_t*)output;
     Cipher();
     Iv = output;
     input += BLOCKLEN;
     output += BLOCKLEN;
     //printf("Step %d - %d", i/16, i);
   }
 
   if (extra)
   {
     memcpy(output, input, extra);
     memset((output + extra), 0, (BLOCKLEN - extra));
     XorWithIv(output);
     state = (state_t*)output;
     Cipher();
   }
 }
 
 void EXAES_CBC_decrypt_buffer(uint8_t* output, uint8_t* input, uint32_t length, const uint8_t* key, const uint8_t* iv)
 {
   uintptr_t i;
   uint8_t extra = length % BLOCKLEN; /* Remaining bytes in the last non-full block */
 
   // Skip the key expansion if key is passed as 0
   if (0 != key)
   {
     Key = key;
     KeyExpansion();
   }
 
   // If iv is passed as 0, we continue to encrypt without re-setting the Iv
   if (iv != 0)
   {
     Iv = (uint8_t*)iv;
   }
 
   for (i = 0; i < length; i += BLOCKLEN)
   {
     memcpy(output, input, BLOCKLEN);
     state = (state_t*)output;
     InvCipher();
     XorWithIv(output);
     Iv = input;
     input += BLOCKLEN;
     output += BLOCKLEN;
   }
 
   if (extra)
   {
     memcpy(output, input, extra);
     state = (state_t*)output;
     InvCipher();
   }
 }
 
 #endif // #if defined(CBC) && (CBC == 1)

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