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tiny-AES-c/aes.c  view on Meta::CPAN

    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);
}
#endif // #if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)

/*****************************************************************************/
/* Public functions:                                                         */
/*****************************************************************************/
#if defined(ECB) && (ECB == 1)


void AES_ECB_encrypt(struct AES_ctx *ctx, uint8_t* buf)
{
  // The next function call encrypts the PlainText with the Key using AES algorithm.
  Cipher((state_t*)buf, ctx->RoundKey);
}

void AES_ECB_decrypt(struct AES_ctx* ctx, uint8_t* buf)
{
  // The next function call decrypts the PlainText with the Key using AES algorithm.
  InvCipher((state_t*)buf, ctx->RoundKey);
}


#endif // #if defined(ECB) && (ECB == 1)





#if defined(CBC) && (CBC == 1)


static void XorWithIv(uint8_t* buf, uint8_t* Iv)
{
  uint8_t i;
  for (i = 0; i < AES_BLOCKLEN; ++i) // The block in AES is always 128bit no matter the key size
  {
    buf[i] ^= Iv[i];
  }
}

void AES_CBC_encrypt_buffer(struct AES_ctx *ctx,uint8_t* buf, uint32_t length)
{
  uintptr_t i;
  uint8_t *Iv = ctx->Iv;
  for (i = 0; i < length; i += AES_BLOCKLEN)
  {
    XorWithIv(buf, Iv);
    Cipher((state_t*)buf, ctx->RoundKey);
    Iv = buf;
    buf += AES_BLOCKLEN;
    //printf("Step %d - %d", i/16, i);
  }
  /* store Iv in ctx for next call */
  memcpy(ctx->Iv, Iv, AES_BLOCKLEN);
}

void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf,  uint32_t length)
{
  uintptr_t i;
  uint8_t storeNextIv[AES_BLOCKLEN];
  for (i = 0; i < length; i += AES_BLOCKLEN)
  {
    memcpy(storeNextIv, buf, AES_BLOCKLEN);
    InvCipher((state_t*)buf, ctx->RoundKey);
    XorWithIv(buf, ctx->Iv);
    memcpy(ctx->Iv, storeNextIv, AES_BLOCKLEN);
    buf += AES_BLOCKLEN;
  }

}

#endif // #if defined(CBC) && (CBC == 1)



#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, uint8_t* buf, uint32_t length)
{
  uint8_t buffer[AES_BLOCKLEN];
  
  unsigned 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);

      /* 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;
    }

    buf[i] = (buf[i] ^ buffer[bi]);
  }
}