text: /*
  
  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
  
  
  
  
  /*****************************************************************************/
  /* Private variables:                                                        */
  /*****************************************************************************/
  // state - array holding the intermediate results during decryption.
  typedef int state_t[4][4];
  
  
  
  // 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 int 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 int 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 the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
  static const int 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-AES-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 AES-128 (as 11 round keys are needed), 
   *  up to rcon[8] for AES-192, up to rcon[7] for AES-256. rcon[0] is not used in AES algorithm."
   */
  
  
  /*****************************************************************************/
  /* Private functions:                                                        */
  /*****************************************************************************/
  /*
  static uint8_t getSBoxValue(uint8_t num)
  {
    return sbox[num];
  }
  */
  #define getSBoxValue(num) (sbox[(num)])
  /*
  static uint8_t getSBoxInvert(uint8_t num)
  {
    return rsbox[num];
  }
  */
  #define getSBoxInvert(num) (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(int* RoundKey, const int* Key)
  {
    unsigned i, j, k;
    int 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.
    for (i = Nk; i < Nb * (Nr + 1); ++i)
    {
      {
        k = (i - 1) * 4;
        tempa[0]=RoundKey[k + 0];
        tempa[1]=RoundKey[k + 1];
        tempa[2]=RoundKey[k + 2];
        tempa[3]=RoundKey[k + 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(AES256) && (AES256 == 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
      j = i * 4; k=(i - Nk) * 4;
      RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
      RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
      RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
      RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
    }
  }
  
  void AES_init_ctx(struct AES_ctx* ctx, const int* key)
  {
    KeyExpansion(ctx->RoundKey, key);
  }
  #if defined(CTR) && (CTR == 1)
  void AES_init_ctx_iv(struct AES_ctx* ctx, const int* key, const int* iv)
  {
    KeyExpansion(ctx->RoundKey, key);
    memcpy (ctx->Iv, iv, AES_BLOCKLEN);
  }
  void AES_ctx_set_iv(struct AES_ctx* ctx, const int* iv)
  {
    memcpy (ctx->Iv, iv, AES_BLOCKLEN);
  }
  #endif
  
  // This function adds the round key to state.
  // The round key is added to the state by an XOR function.
  static void AddRoundKey(int round,state_t* state,int* RoundKey)
  {
    int 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(state_t* state)
  {
    int 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(state_t* state)
  {
    int 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 int xtime(int x)
  {
    return ((x<<1) ^ (((x>>7) & 1) * 0x1b));
  }
  
  // MixColumns function mixes the columns of the state matrix
  static void MixColumns(state_t* state)
  {
    int i;
    int 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 int Multiply(int x, int 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(state_t* state)
  {
    int i;
    int 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(state_t* state)
  {
    int i, j;
    for (i = 0; i < 4; ++i)
    {
      for (j = 0; j < 4; ++j)
      {
        (*state)[j][i] = getSBoxInvert((*state)[j][i]);
      }
    }
  }
  
  static void InvShiftRows(state_t* state)
  {
    int 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(state_t* state, int* RoundKey)
  {
    int round = 0;
  
    // Add the First round key to the state before starting the rounds.
    AddRoundKey(0, state, RoundKey); 
    
    // 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(state);
      ShiftRows(state);
      MixColumns(state);
      AddRoundKey(round, state, RoundKey);
    }
    
    // The last round is given below.
    // The MixColumns function is not here in the last round.
    SubBytes(state);
    ShiftRows(state);
    AddRoundKey(Nr, state, RoundKey);
  }
  
  static void InvCipher(state_t* state,int* RoundKey)
  {
    int round = 0;
  
    // Add the First round key to the state before starting the rounds.
    AddRoundKey(Nr, state, RoundKey); 
  
    // 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(state);
      InvSubBytes(state);
      AddRoundKey(round, state, RoundKey);
      InvMixColumns(state);
    }
    
    // The last round is given below.
    // The MixColumns function is not here in the last round.
    InvShiftRows(state);
    InvSubBytes(state);
    AddRoundKey(0, state, RoundKey);
  }
  
  
  /*****************************************************************************/
  /* Public functions:                                                         */
  /*****************************************************************************/
  #if defined(CTR) && (CTR == 1)
  
  /* Symmetrical operation: same function for encrypting as for decrypting. Note any IV/nonce should never be reused with the same key */
  void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, int* buf,int length)
  {  
    int buffer[AES_BLOCKLEN];
    int i;
    int bi;
    for (i = 0, bi = AES_BLOCKLEN; i < length; ++i, ++bi)
    {
      if (bi == AES_BLOCKLEN) /* we need to regen xor compliment in buffer */
      {
        
        memcpy(buffer, ctx->Iv, AES_BLOCKLEN);
        Cipher((state_t*)buffer,ctx->RoundKey);
        printf("post-cipher\n");
        /* Increment Iv and handle overflow */
        for (bi = (AES_BLOCKLEN - 1); bi >= 0; --bi)
        {
  	      /* inc will owerflow */
          if (ctx->Iv[bi] == 255)
  	      {
            ctx->Iv[bi] = 0;
            continue;
          } 
          ctx->Iv[bi] += 1;
          break;   
        }
        bi = 0;
      }
      // This is the actual encryption
      buf[i] = (buf[i] ^ buffer[bi]);
    }
  }
  
  #endif // #if defined(CTR) && (CTR == 1)
  
  