xtea.c

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/**
 * @file xtea.c
 * @brief XTEA (eXtended TEA)
 *
 * @section License
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Copyright (C) 2010-2024 Oryx Embedded SARL. All rights reserved.
 *
 * This file is part of CycloneCRYPTO Open.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * @author Oryx Embedded SARL (www.oryx-embedded.com)
 * @version 2.4.0
 **/
 
//Switch to the appropriate trace level
#define TRACE_LEVEL CRYPTO_TRACE_LEVEL
 
//Dependencies
#include "core/crypto.h"
#include "cipher/xtea.h"
 
//XTEA magic constant
#define DELTA 0x9E3779B9
 
//Check crypto library configuration
#if (XTEA_SUPPORT == ENABLED)
 
 
//Common interface for encryption algorithms
const CipherAlgo xteaCipherAlgo =
{
   "XTEA",
   sizeof(XteaContext),
   CIPHER_ALGO_TYPE_BLOCK,
   XTEA_BLOCK_SIZE,
   (CipherAlgoInit) xteaInit,
   NULL,
   NULL,
   (CipherAlgoEncryptBlock) xteaEncryptBlock,
   (CipherAlgoDecryptBlock) xteaDecryptBlock,
   (CipherAlgoDeinit) xteaDeinit
};
 
 
/**
 * @brief Key expansion
 * @param[in] context Pointer to the XTEA context to initialize
 * @param[in] key Pointer to the key
 * @param[in] keyLen Length of the key
 * @return Error code
 **/
 
__weak_func error_t xteaInit(XteaContext *context, const uint8_t *key,
   size_t keyLen)
{
   //Check parameters
   if(context == NULL || key == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Invalid key length?
   if(keyLen != 16)
      return ERROR_INVALID_KEY_LENGTH;
 
   //Copy the 128-bit key
   context->k[0] = LOAD32BE(key + 0);
   context->k[1] = LOAD32BE(key + 4);
   context->k[2] = LOAD32BE(key + 8);
   context->k[3] = LOAD32BE(key + 12);
 
   //No error to report
   return NO_ERROR;
}
 
 
/**
 * @brief Encrypt a 16-byte block using XTEA algorithm
 * @param[in] context Pointer to the XTEA context
 * @param[in] input Plaintext block to encrypt
 * @param[out] output Ciphertext block resulting from encryption
 **/
 
__weak_func void xteaEncryptBlock(XteaContext *context, const uint8_t *input,
   uint8_t *output)
{
   uint_t i;
   uint32_t y;
   uint32_t z;
   uint32_t sum;
 
   //Initialize variable
   sum = 0;
 
   //The 8 bytes of plaintext are split into 2 words
   y = LOAD32BE(input + 0);
   z = LOAD32BE(input + 4);
 
   //Apply 32 rounds
   for(i = 0; i < XTEA_NB_ROUNDS; i++)
   {
      y += (((z << 4) ^ (z >> 5)) + z) ^ (sum + context->k[sum & 0x03]);
      sum += DELTA;
      z += (((y << 4) ^ (y >> 5)) + y) ^ (sum + context->k[(sum >> 11) & 0x03]);
   }
 
   //The 2 words of ciphertext are then written as 8 bytes
   STORE32BE(y, output + 0);
   STORE32BE(z, output + 4);
}
 
 
/**
 * @brief Decrypt a 16-byte block using XTEA algorithm
 * @param[in] context Pointer to the XTEA context
 * @param[in] input Ciphertext block to decrypt
 * @param[out] output Plaintext block resulting from decryption
 **/
 
__weak_func void xteaDecryptBlock(XteaContext *context, const uint8_t *input,
   uint8_t *output)
{
   uint_t i;
   uint32_t y;
   uint32_t z;
   uint32_t sum;
 
   //Initialize variable
   sum = (DELTA & 0x07FFFFFF) << 5;
 
   //The 8 bytes of ciphertext are split into 2 words
   y = LOAD32BE(input + 0);
   z = LOAD32BE(input + 4);
 
   //Apply 32 rounds
   for(i = 0; i < XTEA_NB_ROUNDS; i++)
   {
      z -= (((y << 4) ^ (y >> 5)) + y) ^ (sum + context->k[(sum >> 11) & 0x03]);
      sum -= DELTA;
      y -= (((z << 4) ^ (z >> 5)) + z) ^ (sum + context->k[sum & 0x03]);
   }
 
   //The 2 words of plaintext are then written as 8 bytes
   STORE32BE(y, output + 0);
   STORE32BE(z, output + 4);
}
 
 
/**
 * @brief Release XTEA context
 * @param[in] context Pointer to the XTEA context
 **/
 
__weak_func void xteaDeinit(XteaContext *context)
{
   //Clear XTEA context
   osMemset(context, 0, sizeof(XteaContext));
}
 
#endif