stm32l4xx_crypto_cipher.c

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/**
 * @file stm32l4xx_crypto_cipher.c
 * @brief STM32L4 cipher hardware accelerator
 *
 * @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 "stm32l4xx.h"
#include "stm32l4xx_hal.h"
#include "core/crypto.h"
#include "hardware/stm32l4xx/stm32l4xx_crypto.h"
#include "hardware/stm32l4xx/stm32l4xx_crypto_cipher.h"
#include "cipher/cipher_algorithms.h"
#include "cipher_modes/cipher_modes.h"
#include "aead/aead_algorithms.h"
#include "debug.h"
 
//Check crypto library configuration
#if (STM32L4XX_CRYPTO_CIPHER_SUPPORT == ENABLED && AES_SUPPORT == ENABLED)
 
 
/**
 * @brief CRYP module initialization
 * @return Error code
 **/
 
error_t crypInit(void)
{
   //Enable AES peripheral clock
   __HAL_RCC_AES_CLK_ENABLE();
 
   //Successful processing
   return NO_ERROR;
}
 
 
/**
 * @brief Load AES key
 * @param[in] context AES algorithm context
 * @param[in] key Pointer to the key
 **/
 
void aesLoadKey(AesContext *context, const uint32_t *key)
{
   uint32_t temp;
 
   //Read control register
   temp = AES->CR & ~AES_CR_KEYSIZE;
 
   //Check the length of the key
   if(context->nr == 10)
   {
      //10 rounds are required for 128-bit key
      AES->CR = temp | AES_CR_KEYSIZE_128B;
 
      //Set the 128-bit encryption key
      AES->KEYR3 = key[0];
      AES->KEYR2 = key[1];
      AES->KEYR1 = key[2];
      AES->KEYR0 = key[3];
   }
   else
   {
      //14 rounds are required for 256-bit key
      AES->CR = temp | AES_CR_KEYSIZE_256B;
 
      //Set the 256-bit encryption key
      AES->KEYR7 = key[0];
      AES->KEYR6 = key[1];
      AES->KEYR5 = key[2];
      AES->KEYR4 = key[3];
      AES->KEYR3 = key[4];
      AES->KEYR2 = key[5];
      AES->KEYR1 = key[6];
      AES->KEYR0 = key[7];
   }
}
 
 
/**
 * @brief Perform AES encryption or decryption
 * @param[in] context AES algorithm context
 * @param[in,out] iv Initialization vector
 * @param[in] input Data to be encrypted/decrypted
 * @param[out] output Data resulting from the encryption/decryption process
 * @param[in] length Total number of data bytes to be processed
 * @param[in] mode Operation mode
 **/
 
void aesProcessData(AesContext *context, uint8_t *iv, const uint8_t *input,
   uint8_t *output, size_t length, uint32_t mode)
{
   uint32_t temp;
 
   //Acquire exclusive access to the CRYP module
   osAcquireMutex(&stm32l4xxCryptoMutex);
 
   //Disable the AES peripheral and clear the CCF flag
   AES->CR = AES_CR_CCFC;
 
   //Select the chaining mode
   temp = AES->CR & ~(AES_CR_CHMOD | AES_CR_MODE);
   AES->CR = temp | mode;
 
   //Configure the data type
   temp = AES->CR & ~AES_CR_DATATYPE;
   AES->CR = temp | AES_CR_DATATYPE_8B;
 
   //Set encryption key
   if((mode & AES_CR_MODE) == AES_CR_MODE_ENCRYPTION)
   {
      aesLoadKey(context, context->ek);
   }
   else
   {
      aesLoadKey(context, context->dk);
   }
 
   //Valid initialization vector?
   if(iv != NULL)
   {
      //Set initialization vector
      AES->IVR3 = LOAD32BE(iv);
      AES->IVR2 = LOAD32BE(iv + 4);
      AES->IVR1 = LOAD32BE(iv + 8);
      AES->IVR0 = LOAD32BE(iv + 12);
   }
 
   //Enable the AES by setting the EN bit in the AES_CR register
   AES->CR |= AES_CR_EN;
 
   //Process data
   while(length >= AES_BLOCK_SIZE)
   {
      //Write four input data words into the AES_DINR register
      AES->DINR = __UNALIGNED_UINT32_READ(input);
      AES->DINR = __UNALIGNED_UINT32_READ(input + 4);
      AES->DINR = __UNALIGNED_UINT32_READ(input + 8);
      AES->DINR = __UNALIGNED_UINT32_READ(input + 12);
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Read four data words from the AES_DOUTR register
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output + 4, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output + 8, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output + 12, temp);
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
 
      //Next block
      input += AES_BLOCK_SIZE;
      output += AES_BLOCK_SIZE;
      length -= AES_BLOCK_SIZE;
   }
 
   //Process final block of data
   if(length > 0)
   {
      uint32_t buffer[4];
 
      //Copy partial block
      osMemset(buffer, 0, AES_BLOCK_SIZE);
      osMemcpy(buffer, input, length);
 
      //Write four input data words into the AES_DINR register
      AES->DINR = buffer[0];
      AES->DINR = buffer[1];
      AES->DINR = buffer[2];
      AES->DINR = buffer[3];
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Read four data words from the AES_DOUTR register
      buffer[0] = AES->DOUTR;
      buffer[1] = AES->DOUTR;
      buffer[2] = AES->DOUTR;
      buffer[3] = AES->DOUTR;
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
 
      //Discard the data that is not part of the payload
      osMemcpy(output, buffer, length);
   }
 
   //Valid initialization vector?
   if(iv != NULL)
   {
      //Update the value of the initialization vector
      temp = AES->IVR3;
      STORE32BE(temp, iv);
      temp = AES->IVR2;
      STORE32BE(temp, iv + 4);
      temp = AES->IVR1;
      STORE32BE(temp, iv + 8);
      temp = AES->IVR0;
      STORE32BE(temp, iv + 12);
   }
 
   //Disable the AES peripheral by clearing the EN bit of the AES_CR register
   AES->CR = 0;
 
   //Release exclusive access to the CRYP module
   osReleaseMutex(&stm32l4xxCryptoMutex);
}
 
 
/**
 * @brief Key expansion
 * @param[in] context Pointer to the AES context to initialize
 * @param[in] key Pointer to the key
 * @param[in] keyLen Length of the key
 * @return Error code
 **/
 
error_t aesInit(AesContext *context, const uint8_t *key, size_t keyLen)
{
   size_t i;
   uint32_t temp;
 
   //Check parameters
   if(context == NULL || key == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Check the length of the key
   if(keyLen == 16)
   {
      //10 rounds are required for 128-bit key
      context->nr = 10;
   }
   else if(keyLen == 32)
   {
      //14 rounds are required for 256-bit key
      context->nr = 14;
   }
   else
   {
      //192-bit keys are not supported
      return ERROR_INVALID_KEY_LENGTH;
   }
 
   //Determine the number of 32-bit words in the key
   keyLen /= 4;
 
   //Copy the original key
   for(i = 0; i < keyLen; i++)
   {
      context->ek[i] = LOAD32BE(key + (i * 4));
   }
 
   //Disable the AES peripheral and clear the CCF flag
   AES->CR = AES_CR_CCFC;
 
   //Select mode 2 by setting to '01' the MODE bitfield of the AES_CR
   temp = AES->CR & ~AES_CR_CHMOD;
   AES->CR = temp | AES_CR_MODE_KEY_DERIVATION;
 
   //Set encryption key
   aesLoadKey(context, context->ek);
 
   //Enable the AES peripheral, by setting the EN bit of the AES_CR register
   AES->CR |= AES_CR_EN;
 
   //Wait until the CCF flag is set in the AES_SR register
   while((AES->SR & AES_SR_CCF) == 0)
   {
   }
 
   //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
   AES->CR |= AES_CR_CCFC;
 
   //Check the length of the key
   if(context->nr == 10)
   {
      //Read the AES_KEYRx registers to obtain the 128-bit decryption key
      context->dk[0] = AES->KEYR3;
      context->dk[1] = AES->KEYR2;
      context->dk[2] = AES->KEYR1;
      context->dk[3] = AES->KEYR0;
   }
   else if(context->nr == 14)
   {
      //Read the AES_KEYRx registers to obtain the 256-bit decryption key
      context->dk[0] = AES->KEYR7;
      context->dk[1] = AES->KEYR6;
      context->dk[2] = AES->KEYR5;
      context->dk[3] = AES->KEYR4;
      context->dk[4] = AES->KEYR3;
      context->dk[5] = AES->KEYR2;
      context->dk[6] = AES->KEYR1;
      context->dk[7] = AES->KEYR0;
   }
   else
   {
      //Report an error
      return ERROR_INVALID_KEY_LENGTH;
   }
 
   //The AES is disabled by hardware when the derivation key is available
   return NO_ERROR;
}
 
 
/**
 * @brief Encrypt a 16-byte block using AES algorithm
 * @param[in] context Pointer to the AES context
 * @param[in] input Plaintext block to encrypt
 * @param[out] output Ciphertext block resulting from encryption
 **/
 
void aesEncryptBlock(AesContext *context, const uint8_t *input, uint8_t *output)
{
   //Perform AES encryption
   aesProcessData(context, NULL, input, output, AES_BLOCK_SIZE,
      AES_CR_CHMOD_ECB | AES_CR_MODE_ENCRYPTION);
}
 
 
/**
 * @brief Decrypt a 16-byte block using AES algorithm
 * @param[in] context Pointer to the AES context
 * @param[in] input Ciphertext block to decrypt
 * @param[out] output Plaintext block resulting from decryption
 **/
 
void aesDecryptBlock(AesContext *context, const uint8_t *input, uint8_t *output)
{
   //Perform AES decryption
   aesProcessData(context, NULL, input, output, AES_BLOCK_SIZE,
      AES_CR_CHMOD_ECB | AES_CR_MODE_DECRYPTION);
}
 
 
#if (ECB_SUPPORT == ENABLED)
 
/**
 * @brief ECB encryption
 * @param[in] cipher Cipher algorithm
 * @param[in] context Cipher algorithm context
 * @param[in] p Plaintext to be encrypted
 * @param[out] c Ciphertext resulting from the encryption
 * @param[in] length Total number of data bytes to be encrypted
 * @return Error code
 **/
 
error_t ecbEncrypt(const CipherAlgo *cipher, void *context,
   const uint8_t *p, uint8_t *c, size_t length)
{
   error_t error;
 
   //Initialize status code
   error = NO_ERROR;
 
   //AES cipher algorithm?
   if(cipher == AES_CIPHER_ALGO)
   {
      //Check the length of the payload
      if(length == 0)
      {
         //No data to process
      }
      else if((length % AES_BLOCK_SIZE) == 0)
      {
         //Encrypt payload data
         aesProcessData(context, NULL, p, c, length, AES_CR_CHMOD_ECB |
            AES_CR_MODE_ENCRYPTION);
      }
      else
      {
         //The length of the payload must be a multiple of the block size
         error = ERROR_INVALID_LENGTH;
      }
   }
   else
   {
      //ECB mode operates in a block-by-block fashion
      while(length >= cipher->blockSize)
      {
         //Encrypt current block
         cipher->encryptBlock(context, p, c);
 
         //Next block
         p += cipher->blockSize;
         c += cipher->blockSize;
         length -= cipher->blockSize;
      }
 
      //The length of the payload must be a multiple of the block size
      if(length != 0)
      {
         error = ERROR_INVALID_LENGTH;
      }
   }
 
   //Return status code
   return error;
}
 
 
/**
 * @brief ECB decryption
 * @param[in] cipher Cipher algorithm
 * @param[in] context Cipher algorithm context
 * @param[in] c Ciphertext to be decrypted
 * @param[out] p Plaintext resulting from the decryption
 * @param[in] length Total number of data bytes to be decrypted
 * @return Error code
 **/
 
error_t ecbDecrypt(const CipherAlgo *cipher, void *context,
   const uint8_t *c, uint8_t *p, size_t length)
{
   error_t error;
 
   //Initialize status code
   error = NO_ERROR;
 
   //AES cipher algorithm?
   if(cipher == AES_CIPHER_ALGO)
   {
      //Check the length of the payload
      if(length == 0)
      {
         //No data to process
      }
      else if((length % AES_BLOCK_SIZE) == 0)
      {
         //Decrypt payload data
         aesProcessData(context, NULL, c, p, length, AES_CR_CHMOD_ECB |
            AES_CR_MODE_DECRYPTION);
      }
      else
      {
         //The length of the payload must be a multiple of the block size
         error = ERROR_INVALID_LENGTH;
      }
   }
   else
   {
      //ECB mode operates in a block-by-block fashion
      while(length >= cipher->blockSize)
      {
         //Decrypt current block
         cipher->decryptBlock(context, c, p);
 
         //Next block
         c += cipher->blockSize;
         p += cipher->blockSize;
         length -= cipher->blockSize;
      }
 
      //The length of the payload must be a multiple of the block size
      if(length != 0)
      {
         error = ERROR_INVALID_LENGTH;
      }
   }
 
   //Return status code
   return error;
}
 
#endif
#if (CBC_SUPPORT == ENABLED)
 
/**
 * @brief CBC encryption
 * @param[in] cipher Cipher algorithm
 * @param[in] context Cipher algorithm context
 * @param[in,out] iv Initialization vector
 * @param[in] p Plaintext to be encrypted
 * @param[out] c Ciphertext resulting from the encryption
 * @param[in] length Total number of data bytes to be encrypted
 * @return Error code
 **/
 
error_t cbcEncrypt(const CipherAlgo *cipher, void *context,
   uint8_t *iv, const uint8_t *p, uint8_t *c, size_t length)
{
   error_t error;
 
   //Initialize status code
   error = NO_ERROR;
 
   //AES cipher algorithm?
   if(cipher == AES_CIPHER_ALGO)
   {
      //Check the length of the payload
      if(length == 0)
      {
         //No data to process
      }
      else if((length % AES_BLOCK_SIZE) == 0)
      {
         //Encrypt payload data
         aesProcessData(context, iv, p, c, length, AES_CR_CHMOD_CBC |
            AES_CR_MODE_ENCRYPTION);
      }
      else
      {
         //The length of the payload must be a multiple of the block size
         error = ERROR_INVALID_LENGTH;
      }
   }
   else
   {
      size_t i;
 
      //CBC mode operates in a block-by-block fashion
      while(length >= cipher->blockSize)
      {
         //XOR input block with IV contents
         for(i = 0; i < cipher->blockSize; i++)
         {
            c[i] = p[i] ^ iv[i];
         }
 
         //Encrypt the current block based upon the output of the previous
         //encryption
         cipher->encryptBlock(context, c, c);
 
         //Update IV with output block contents
         osMemcpy(iv, c, cipher->blockSize);
 
         //Next block
         p += cipher->blockSize;
         c += cipher->blockSize;
         length -= cipher->blockSize;
      }
 
      //The length of the payload must be a multiple of the block size
      if(length != 0)
      {
         error = ERROR_INVALID_LENGTH;
      }
   }
 
   //Return status code
   return error;
}
 
 
/**
 * @brief CBC decryption
 * @param[in] cipher Cipher algorithm
 * @param[in] context Cipher algorithm context
 * @param[in,out] iv Initialization vector
 * @param[in] c Ciphertext to be decrypted
 * @param[out] p Plaintext resulting from the decryption
 * @param[in] length Total number of data bytes to be decrypted
 * @return Error code
 **/
 
error_t cbcDecrypt(const CipherAlgo *cipher, void *context,
   uint8_t *iv, const uint8_t *c, uint8_t *p, size_t length)
{
   error_t error;
 
   //Initialize status code
   error = NO_ERROR;
 
   //AES cipher algorithm?
   if(cipher == AES_CIPHER_ALGO)
   {
      //Check the length of the payload
      if(length == 0)
      {
         //No data to process
      }
      else if((length % AES_BLOCK_SIZE) == 0)
      {
         //Decrypt payload data
         aesProcessData(context, iv, c, p, length, AES_CR_CHMOD_CBC |
            AES_CR_MODE_DECRYPTION);
      }
      else
      {
         //The length of the payload must be a multiple of the block size
         error = ERROR_INVALID_LENGTH;
      }
   }
   else
   {
      size_t i;
      uint8_t t[16];
 
      //CBC mode operates in a block-by-block fashion
      while(length >= cipher->blockSize)
      {
         //Save input block
         osMemcpy(t, c, cipher->blockSize);
 
         //Decrypt the current block
         cipher->decryptBlock(context, c, p);
 
         //XOR output block with IV contents
         for(i = 0; i < cipher->blockSize; i++)
         {
            p[i] ^= iv[i];
         }
 
         //Update IV with input block contents
         osMemcpy(iv, t, cipher->blockSize);
 
         //Next block
         c += cipher->blockSize;
         p += cipher->blockSize;
         length -= cipher->blockSize;
      }
 
      //The length of the payload must be a multiple of the block size
      if(length != 0)
      {
         error = ERROR_INVALID_LENGTH;
      }
   }
 
   //Return status code
   return error;
}
 
#endif
#if (CTR_SUPPORT == ENABLED)
 
/**
 * @brief CTR encryption
 * @param[in] cipher Cipher algorithm
 * @param[in] context Cipher algorithm context
 * @param[in] m Size in bits of the specific part of the block to be incremented
 * @param[in,out] t Initial counter block
 * @param[in] p Plaintext to be encrypted
 * @param[out] c Ciphertext resulting from the encryption
 * @param[in] length Total number of data bytes to be encrypted
 * @return Error code
 **/
 
error_t ctrEncrypt(const CipherAlgo *cipher, void *context, uint_t m,
   uint8_t *t, const uint8_t *p, uint8_t *c, size_t length)
{
   error_t error;
 
   //Initialize status code
   error = NO_ERROR;
 
   //AES cipher algorithm?
   if(cipher == AES_CIPHER_ALGO)
   {
      //Check the value of the parameter
      if(m == (AES_BLOCK_SIZE * 8))
      {
         //Check the length of the payload
         if(length > 0)
         {
            //Encrypt payload data
            aesProcessData(context, t, p, c, length, AES_CR_CHMOD_CTR |
               AES_CR_MODE_ENCRYPTION);
         }
         else
         {
            //No data to process
         }
      }
      else
      {
         //The value of the parameter is not valid
         error = ERROR_INVALID_PARAMETER;
      }
   }
   else
   {
      //Check the value of the parameter
      if((m % 8) == 0 && m <= (cipher->blockSize * 8))
      {
         size_t i;
         size_t n;
         uint16_t temp;
         uint8_t o[16];
 
         //Determine the size, in bytes, of the specific part of the block
         //to be incremented
         m = m / 8;
 
         //Process plaintext
         while(length > 0)
         {
            //CTR mode operates in a block-by-block fashion
            n = MIN(length, cipher->blockSize);
 
            //Compute O(j) = CIPH(T(j))
            cipher->encryptBlock(context, t, o);
 
            //Compute C(j) = P(j) XOR T(j)
            for(i = 0; i < n; i++)
            {
               c[i] = p[i] ^ o[i];
            }
 
            //Standard incrementing function
            for(temp = 1, i = 1; i <= m; i++)
            {
               //Increment the current byte and propagate the carry
               temp += t[cipher->blockSize - i];
               t[cipher->blockSize - i] = temp & 0xFF;
               temp >>= 8;
            }
 
            //Next block
            p += n;
            c += n;
            length -= n;
         }
      }
      else
      {
         //The value of the parameter is not valid
         error = ERROR_INVALID_PARAMETER;
      }
   }
 
   //Return status code
   return error;
}
 
#endif
#if (GCM_SUPPORT == ENABLED)
 
/**
 * @brief Perform AES-GCM encryption or decryption
 * @param[in] context AES algorithm context
 * @param[in] iv Initialization vector
 * @param[in] a Additional authenticated data
 * @param[in] aLen Length of the additional data
 * @param[in] input Data to be encrypted/decrypted
 * @param[out] output Data resulting from the encryption/decryption process
 * @param[in] length Total number of data bytes to be processed
 * @param[out] t Authentication tag
 * @param[in] mode Operation mode
 **/
 
void gcmProcessData(AesContext *context, const uint8_t *iv,
   const uint8_t *a, size_t aLen, const uint8_t *input, uint8_t *output,
   size_t length, uint8_t *t, uint32_t mode)
{
   size_t n;
   uint64_t m;
   uint32_t temp;
   uint32_t buffer[4];
 
   //Acquire exclusive access to the AES module
   osAcquireMutex(&stm32l4xxCryptoMutex);
 
   //Disable the AES peripheral and clear the CCF flag
   AES->CR = AES_CR_CCFC;
 
   //Select GCM chaining mode, by setting to '011' the CHMOD bitfield of the
   //AES_CR register
   temp = AES->CR & ~AES_CR_CHMOD;
   AES->CR = temp | AES_CR_CHMOD_GCM_GMAC;
 
   //Set to '00' (no data swapping) the DATATYPE bitfield
   temp = AES->CR & ~AES_CR_DATATYPE;
   AES->CR = temp | AES_CR_DATATYPE_32B;
 
   //Indicate the Init phase, by setting to '00' the GCMPH bitfield of the
   //AES_CR register
   temp = AES->CR & ~AES_CR_GCMPH;
   AES->CR = temp | AES_CR_GCMPH_INIT;
 
   //Set the MODE bitfield of the AES_CR register to '00' or '10'
   temp = AES->CR & ~AES_CR_MODE;
   AES->CR = temp | mode;
 
   //Set encryption key
   aesLoadKey(context, context->ek);
 
   //Set initialization vector
   AES->IVR3 = LOAD32BE(iv);
   AES->IVR2 = LOAD32BE(iv + 4);
   AES->IVR1 = LOAD32BE(iv + 8);
   AES->IVR0 = 2;
 
   //Start the calculation of the hash key, by setting to 1 the EN bit of the
   //AES_CR register
   AES->CR |= AES_CR_EN;
 
   //Wait until the end of computation, indicated by the CCF flag of the AES_SR
   //transiting to 1
   while((AES->SR & AES_SR_CCF) == 0)
   {
   }
 
   //Clear the CCF flag of the AES_SR register, by setting to 1 the CCFC bit
   //of the AES_CR register
   AES->CR |= AES_CR_CCFC;
 
   //Configure the data type
   temp = AES->CR & ~AES_CR_DATATYPE;
   AES->CR = temp | AES_CR_DATATYPE_8B;
 
   //Indicate the Header phase, by setting to '01' the GCMPH bitfield of the
   //AES_CR register
   temp = AES->CR & ~AES_CR_GCMPH;
   AES->CR = temp | AES_CR_GCMPH_HEADER;
 
   //Enable the AES peripheral by setting the EN bit of the AES_CR register
   AES->CR |= AES_CR_EN;
 
   //Process additional authenticated data
   for(n = aLen; n >= AES_BLOCK_SIZE; n -= AES_BLOCK_SIZE)
   {
      //Write four input data words into the AES_DINR register
      AES->DINR = __UNALIGNED_UINT32_READ(a);
      AES->DINR = __UNALIGNED_UINT32_READ(a + 4);
      AES->DINR = __UNALIGNED_UINT32_READ(a + 8);
      AES->DINR = __UNALIGNED_UINT32_READ(a + 12);
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
 
      //Next block
      a += AES_BLOCK_SIZE;
   }
 
   //Process final block of additional authenticated data
   if(n > 0)
   {
      //If the AAD size in the last block is inferior to 128 bits, pad the
      //remainder of the block with zeros
      osMemset(buffer, 0, AES_BLOCK_SIZE);
      osMemcpy(buffer, a, n);
 
      //Write four input data words into the AES_DINR register
      AES->DINR = buffer[0];
      AES->DINR = buffer[1];
      AES->DINR = buffer[2];
      AES->DINR = buffer[3];
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
   }
 
   //Indicate the Payload phase, by setting to '10' the GCMPH bitfield of the
   //AES_CR register
   temp = AES->CR & ~AES_CR_GCMPH;
   AES->CR = temp | AES_CR_GCMPH_PAYLOAD;
 
   //Process data
   for(n = length; n >= AES_BLOCK_SIZE; n -= AES_BLOCK_SIZE)
   {
      //Write four input data words into the AES_DINR register
      AES->DINR = __UNALIGNED_UINT32_READ(input);
      AES->DINR = __UNALIGNED_UINT32_READ(input + 4);
      AES->DINR = __UNALIGNED_UINT32_READ(input + 8);
      AES->DINR = __UNALIGNED_UINT32_READ(input + 12);
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Read four data words from the AES_DOUTR register
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output + 4, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output + 8, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output + 12, temp);
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
 
      //Next block
      input += AES_BLOCK_SIZE;
      output += AES_BLOCK_SIZE;
   }
 
   //Process final block of data
   if(n > 0)
   {
      //If it is the last block and the plaintext (encryption) or ciphertext
      //(decryption) size in the block is inferior to 128 bits, pad the
      //remainder of the block with zeros
      osMemset(buffer, 0, AES_BLOCK_SIZE);
      osMemcpy(buffer, input, n);
 
#if !defined(AES_CR_NPBLB)
      //Workaround for GCM encryption mode
      if((mode & AES_CR_MODE) == AES_CR_MODE_ENCRYPTION)
      {
         //Switch the AES mode to CTR mode by writing the bitfield CHMOD to
         //'010' in the AES_CR register
         temp = AES->CR & ~AES_CR_CHMOD;
         AES->CR = temp | AES_CR_CHMOD_CTR;
      }
#else
      //Specify the number of padding bytes in the last block
      temp = AES->CR & ~AES_CR_NPBLB;
      AES->CR = temp | ((AES_BLOCK_SIZE - n) << AES_CR_NPBLB_Pos);
#endif
 
      //Write four input data words into the AES_DINR register
      AES->DINR = buffer[0];
      AES->DINR = buffer[1];
      AES->DINR = buffer[2];
      AES->DINR = buffer[3];
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Read four data words from the AES_DOUTR register
      buffer[0] = AES->DOUTR;
      buffer[1] = AES->DOUTR;
      buffer[2] = AES->DOUTR;
      buffer[3] = AES->DOUTR;
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
 
      //Discard the bits that are not part of the payload when the last block
      //size is less than 16 bytes
      osMemcpy(output, buffer, n);
 
#if !defined(AES_CR_NPBLB)
      //Workaround for GCM encryption mode
      if((mode & AES_CR_MODE) == AES_CR_MODE_ENCRYPTION)
      {
         //In the intermediate data, set to zero the bits corresponding to
         //the padded bits of the last block of payload
         osMemset((uint8_t *) buffer + n, 0, AES_BLOCK_SIZE - n);
 
         //Change the AES mode to GCM mode by writing the bitfield CHMOD to
         //'011' in the AES_CR register
         temp = AES->CR & ~AES_CR_CHMOD;
         AES->CR = temp | AES_CR_CHMOD_GCM_GMAC;
 
         //Select Final phase by writing the bitfield GCMPH to '11' in the
         //AES_CR register
         temp = AES->CR & ~AES_CR_GCMPH;
         AES->CR = temp | AES_CR_GCMPH_FINAL;
 
         //Write four input data words into the AES_DINR register
         AES->DINR = buffer[0];
         AES->DINR = buffer[1];
         AES->DINR = buffer[2];
         AES->DINR = buffer[3];
 
         //Wait until the CCF flag is set in the AES_SR register
         while((AES->SR & AES_SR_CCF) == 0)
         {
         }
 
         //Upon completion, read the AES_DOUTR register. The data itself has no
         //importance and can be ignored. This step is required to set up the
         //internal state machine in a way for it to handle correctly the TAG
         //generation during the GCM final phase
         buffer[0] = AES->DOUTR;
         buffer[1] = AES->DOUTR;
         buffer[2] = AES->DOUTR;
         buffer[3] = AES->DOUTR;
 
         //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
         AES->CR |= AES_CR_CCFC;
      }
#endif
   }
 
   //Indicate the Final phase, by setting to '11' the GCMPH bitfield of the
   //AES_CR register
   temp = AES->CR & ~AES_CR_GCMPH;
   AES->CR = temp | AES_CR_GCMPH_FINAL;
 
   //Select encrypt mode by setting to '00' the MODE bitfield of the AES_CR
   //register
   temp = AES->CR & ~AES_CR_MODE;
   AES->CR = temp | AES_CR_MODE_ENCRYPTION;
 
#if !defined(AES_CR_NPBLB)
   //Compose the data of the block, by concatenating the AAD bit length and
   //the payload bit length. Write the block into the AES_DINR register
   m = aLen * 8;
   AES->DINR = htobe32(m >> 32);
   AES->DINR = htobe32(m);
   m = length * 8;
   AES->DINR = htobe32(m >> 32);
   AES->DINR = htobe32(m);
#else
   //Compose the data of the block, by concatenating the AAD bit length and
   //the payload bit length. Write the block into the AES_DINR register without
   //swapping
   m = aLen * 8;
   AES->DINR = htole32(m >> 32);
   AES->DINR = htole32(m);
   m = length * 8;
   AES->DINR = htole32(m >> 32);
   AES->DINR = htole32(m);
#endif
 
   //Wait until the end of computation, indicated by the CCF flag of the AES_SR
   //transiting to 1
   while((AES->SR & AES_SR_CCF) == 0)
   {
   }
 
   //Get the GCM authentication tag, by reading the AES_DOUTR register four
   //times
   temp = AES->DOUTR;
   __UNALIGNED_UINT32_WRITE(t, temp);
   temp = AES->DOUTR;
   __UNALIGNED_UINT32_WRITE(t + 4, temp);
   temp = AES->DOUTR;
   __UNALIGNED_UINT32_WRITE(t + 8, temp);
   temp = AES->DOUTR;
   __UNALIGNED_UINT32_WRITE(t + 12, temp);
 
   //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
   AES->CR |= AES_CR_CCFC;
 
   //Disable the AES peripheral by clearing the EN bit of the AES_CR register
   AES->CR = 0;
 
   //Release exclusive access to the AES module
   osReleaseMutex(&stm32l4xxCryptoMutex);
}
 
 
/**
 * @brief Initialize GCM context
 * @param[in] context Pointer to the GCM context
 * @param[in] cipherAlgo Cipher algorithm
 * @param[in] cipherContext Pointer to the cipher algorithm context
 * @return Error code
 **/
 
error_t gcmInit(GcmContext *context, const CipherAlgo *cipherAlgo,
   void *cipherContext)
{
   //Check parameters
   if(context == NULL || cipherContext == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //The CRYP module only supports AES cipher algorithm
   if(cipherAlgo != AES_CIPHER_ALGO)
      return ERROR_INVALID_PARAMETER;
 
   //Save cipher algorithm context
   context->cipherAlgo = cipherAlgo;
   context->cipherContext = cipherContext;
 
   //Successful initialization
   return NO_ERROR;
}
 
 
/**
 * @brief Authenticated encryption using GCM
 * @param[in] context Pointer to the GCM context
 * @param[in] iv Initialization vector
 * @param[in] ivLen Length of the initialization vector
 * @param[in] a Additional authenticated data
 * @param[in] aLen Length of the additional data
 * @param[in] p Plaintext to be encrypted
 * @param[out] c Ciphertext resulting from the encryption
 * @param[in] length Total number of data bytes to be encrypted
 * @param[out] t Authentication tag
 * @param[in] tLen Length of the authentication tag
 * @return Error code
 **/
 
error_t gcmEncrypt(GcmContext *context, const uint8_t *iv,
   size_t ivLen, const uint8_t *a, size_t aLen, const uint8_t *p,
   uint8_t *c, size_t length, uint8_t *t, size_t tLen)
{
   uint8_t authTag[16];
 
   //Make sure the GCM context is valid
   if(context == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Check whether the length of the IV is 96 bits
   if(ivLen != 12)
      return ERROR_INVALID_LENGTH;
 
   //Check the length of the authentication tag
   if(tLen < 4 || tLen > 16)
      return ERROR_INVALID_LENGTH;
 
   //Perform AES-GCM encryption
   gcmProcessData(context->cipherContext, iv, a, aLen, p, c, length,
      authTag, AES_CR_MODE_ENCRYPTION);
 
   //Copy the resulting authentication tag
   osMemcpy(t, authTag, tLen);
 
   //Successful processing
   return NO_ERROR;
}
 
 
/**
 * @brief Authenticated decryption using GCM
 * @param[in] context Pointer to the GCM context
 * @param[in] iv Initialization vector
 * @param[in] ivLen Length of the initialization vector
 * @param[in] a Additional authenticated data
 * @param[in] aLen Length of the additional data
 * @param[in] c Ciphertext to be decrypted
 * @param[out] p Plaintext resulting from the decryption
 * @param[in] length Total number of data bytes to be decrypted
 * @param[in] t Authentication tag
 * @param[in] tLen Length of the authentication tag
 * @return Error code
 **/
 
error_t gcmDecrypt(GcmContext *context, const uint8_t *iv,
   size_t ivLen, const uint8_t *a, size_t aLen, const uint8_t *c,
   uint8_t *p, size_t length, const uint8_t *t, size_t tLen)
{
   size_t i;
   uint8_t mask;
   uint8_t authTag[16];
 
   //Make sure the GCM context is valid
   if(context == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Check whether the length of the IV is 96 bits
   if(ivLen != 12)
      return ERROR_INVALID_LENGTH;
 
   //Check the length of the authentication tag
   if(tLen < 4 || tLen > 16)
      return ERROR_INVALID_LENGTH;
 
   //Perform AES-GCM decryption
   gcmProcessData(context->cipherContext, iv, a, aLen, c, p, length,
      authTag, AES_CR_MODE_DECRYPTION);
 
   //The calculated tag is bitwise compared to the received tag
   for(mask = 0, i = 0; i < tLen; i++)
   {
      mask |= authTag[i] ^ t[i];
   }
 
   //The message is authenticated if and only if the tags match
   return (mask == 0) ? NO_ERROR : ERROR_FAILURE;
}
 
#endif
#if (CCM_SUPPORT == ENABLED && defined(AES_CR_NPBLB))
 
/**
 * @brief Perform AES-CCM encryption or decryption
 * @param[in] context AES algorithm context
 * @param[in] b0 Pointer to the B0 block
 * @param[in] a Additional authenticated data
 * @param[in] aLen Length of the additional data
 * @param[in] input Data to be encrypted/decrypted
 * @param[out] output Data resulting from the encryption/decryption process
 * @param[in] length Total number of data bytes to be processed
 * @param[out] t Authentication tag
 * @param[in] mode Operation mode
 **/
 
void ccmProcessData(AesContext *context, const uint8_t *b0, const uint8_t *a,
   size_t aLen, const uint8_t *input, uint8_t *output, size_t length,
   uint8_t *t, uint32_t mode)
{
   size_t n;
   uint32_t temp;
   uint8_t buffer[16];
 
   //Acquire exclusive access to the AES module
   osAcquireMutex(&stm32l4xxCryptoMutex);
 
   //Disable the AES peripheral and clear the CCF flag
   AES->CR = AES_CR_CCFC;
 
   //Select CCM chaining mode, by setting to '100' the CHMOD bitfield of the
   //AES_CR register
   temp = AES->CR & ~AES_CR_CHMOD;
   AES->CR = temp | AES_CR_CHMOD_CCM;
 
   //Configure the data type
   temp = AES->CR & ~AES_CR_DATATYPE;
   AES->CR = temp | AES_CR_DATATYPE_8B;
 
   //Indicate the Init phase, by setting to '00' the GCMPH bitfield of the
   //AES_CR register
   temp = AES->CR & ~AES_CR_GCMPH;
   AES->CR = temp | AES_CR_GCMPH_INIT;
 
   //Set the MODE bitfield of the AES_CR register to '00' or '10'. Although
   //the bitfield is only used in payload phase, it is recommended to set it
   //in the Init phase and keep it unchanged in all subsequent phases
   temp = AES->CR & ~AES_CR_MODE;
   AES->CR = temp | mode;
 
   //Set encryption key
   aesLoadKey(context, context->ek);
 
   //Initialize AES_IVRx registers with B0 data
   AES->IVR3 = LOAD32BE(b0);
   AES->IVR2 = LOAD32BE(b0 + 4);
   AES->IVR1 = LOAD32BE(b0 + 8);
   AES->IVR0 = LOAD32BE(b0 + 12);
 
   //Start the calculation of the counter, by setting to 1 the EN bit of the
   //AES_CR register
   AES->CR |= AES_CR_EN;
 
   //Wait until the end of computation, indicated by the CCF flag of the AES_SR
   //transiting to 1
   while((AES->SR & AES_SR_CCF) == 0)
   {
   }
 
   //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
   AES->CR |= AES_CR_CCFC;
 
   //Indicate the Header phase, by setting to '01' the GCMPH bitfield of
   //the AES_CR register
   temp = AES->CR & ~AES_CR_GCMPH;
   AES->CR = temp | AES_CR_GCMPH_HEADER;
 
   //Enable the AES peripheral by setting the EN bit of the AES_CR register
   AES->CR |= AES_CR_EN;
 
   //The header phase can be skipped if there is no associated data
   if(aLen > 0)
   {
      //The first block of the associated data (B1) must be formatted by
      //software, with the associated data length
      osMemset(buffer, 0, 16);
 
      //Check the length of the associated data string
      if(aLen < 0xFF00)
      {
         //The length is encoded as 2 octets
         STORE16BE(aLen, buffer);
 
         //Number of bytes to copy
         n = MIN(aLen, 16 - 2);
         //Concatenate the associated data A
         osMemcpy(buffer + 2, a, n);
      }
      else
      {
         //The length is encoded as 6 octets
         buffer[0] = 0xFF;
         buffer[1] = 0xFE;
 
         //MSB is stored first
         STORE32BE(aLen, buffer + 2);
 
         //Number of bytes to copy
         n = MIN(aLen, 16 - 6);
         //Concatenate the associated data A
         osMemcpy(buffer + 6, a, n);
      }
 
      //Write four input data words into the AES_DINR register
      AES->DINR = LOAD32LE(buffer);
      AES->DINR = LOAD32LE(buffer + 4);
      AES->DINR = LOAD32LE(buffer + 8);
      AES->DINR = LOAD32LE(buffer + 12);
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
 
      //Number of remaining data bytes
      aLen -= n;
      a += n;
   }
 
   //Process additional authenticated data
   while(aLen >= AES_BLOCK_SIZE)
   {
      //Write four input data words into the AES_DINR register
      AES->DINR = __UNALIGNED_UINT32_READ(a);
      AES->DINR = __UNALIGNED_UINT32_READ(a + 4);
      AES->DINR = __UNALIGNED_UINT32_READ(a + 8);
      AES->DINR = __UNALIGNED_UINT32_READ(a + 12);
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
 
      //Next block
      a += AES_BLOCK_SIZE;
      aLen -= AES_BLOCK_SIZE;
   }
 
   //Process final block of additional authenticated data
   if(aLen > 0)
   {
      //If the AAD size in the last block is inferior to 128 bits, pad the
      //remainder of the block with zeros
      osMemset(buffer, 0, AES_BLOCK_SIZE);
      osMemcpy(buffer, a, aLen);
 
      //Write four input data words into the AES_DINR register
      AES->DINR = __UNALIGNED_UINT32_READ(buffer);
      AES->DINR = __UNALIGNED_UINT32_READ(buffer + 4);
      AES->DINR = __UNALIGNED_UINT32_READ(buffer + 8);
      AES->DINR = __UNALIGNED_UINT32_READ(buffer + 12);
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
   }
 
   //Indicate the Payload phase, by setting to '10' the GCMPH bitfield of the
   //AES_CR register
   temp = AES->CR & ~AES_CR_GCMPH;
   AES->CR = temp | AES_CR_GCMPH_PAYLOAD;
 
   //Process data
   while(length >= AES_BLOCK_SIZE)
   {
      //Write four input data words into the AES_DINR register
      AES->DINR = __UNALIGNED_UINT32_READ(input);
      AES->DINR = __UNALIGNED_UINT32_READ(input + 4);
      AES->DINR = __UNALIGNED_UINT32_READ(input + 8);
      AES->DINR = __UNALIGNED_UINT32_READ(input + 12);
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Read four data words from the AES_DOUTR register
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output + 4, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output + 8, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(output + 12, temp);
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
 
      //Next block
      input += AES_BLOCK_SIZE;
      output += AES_BLOCK_SIZE;
      length -= AES_BLOCK_SIZE;
   }
 
   //Process final block of data
   if(length > 0)
   {
      //If it is the last block and the plaintext (encryption) or ciphertext
      //(decryption) size in the block is inferior to 128 bits, pad the
      //remainder of the block with zeros
      osMemset(buffer, 0, AES_BLOCK_SIZE);
      osMemcpy(buffer, input, length);
 
      //Decryption operation?
      if((mode & AES_CR_MODE) == AES_CR_MODE_DECRYPTION)
      {
         //Specify the number of padding bytes in the last block
         temp = AES->CR & ~AES_CR_NPBLB;
         AES->CR = temp | ((AES_BLOCK_SIZE - length) << AES_CR_NPBLB_Pos);
      }
 
      //Write four input data words into the AES_DINR register
      AES->DINR = __UNALIGNED_UINT32_READ(buffer);
      AES->DINR = __UNALIGNED_UINT32_READ(buffer + 4);
      AES->DINR = __UNALIGNED_UINT32_READ(buffer + 8);
      AES->DINR = __UNALIGNED_UINT32_READ(buffer + 12);
 
      //Wait until the CCF flag is set in the AES_SR register
      while((AES->SR & AES_SR_CCF) == 0)
      {
      }
 
      //Read four data words from the AES_DOUTR register
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(buffer, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(buffer + 4, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(buffer + 8, temp);
      temp = AES->DOUTR;
      __UNALIGNED_UINT32_WRITE(buffer + 12, temp);
 
      //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
      AES->CR |= AES_CR_CCFC;
 
      //Discard the bits that are not part of the payload when the last block
      //size is less than 16 bytes
      osMemcpy(output, buffer, length);
   }
 
   //Indicate the Final phase, by setting to '11' the GCMPH bitfield of the
   //AES_CR register
   temp = AES->CR & ~AES_CR_GCMPH;
   AES->CR = temp | AES_CR_GCMPH_FINAL;
 
   //Wait until the end of computation, indicated by the CCF flag of the AES_SR
   //transiting to 1
   while((AES->SR & AES_SR_CCF) == 0)
   {
   }
 
   //Get the CCM authentication tag, by reading the AES_DOUTR register four
   //times
   temp = AES->DOUTR;
   __UNALIGNED_UINT32_WRITE(t, temp);
   temp = AES->DOUTR;
   __UNALIGNED_UINT32_WRITE(t + 4, temp);
   temp = AES->DOUTR;
   __UNALIGNED_UINT32_WRITE(t + 8, temp);
   temp = AES->DOUTR;
   __UNALIGNED_UINT32_WRITE(t + 12, temp);
 
   //Clear the CCF flag, by setting the CCFC bit of the AES_CR register
   AES->CR |= AES_CR_CCFC;
 
   //Disable the AES peripheral by clearing the EN bit of the AES_CR register
   AES->CR = 0;
 
   //Release exclusive access to the AES module
   osReleaseMutex(&stm32l4xxCryptoMutex);
}
 
 
/**
 * @brief Authenticated encryption using CCM
 * @param[in] cipher Cipher algorithm
 * @param[in] context Cipher algorithm context
 * @param[in] n Nonce
 * @param[in] nLen Length of the nonce
 * @param[in] a Additional authenticated data
 * @param[in] aLen Length of the additional data
 * @param[in] p Plaintext to be encrypted
 * @param[out] c Ciphertext resulting from the encryption
 * @param[in] length Total number of data bytes to be encrypted
 * @param[out] t MAC resulting from the encryption process
 * @param[in] tLen Length of the MAC
 * @return Error code
 **/
 
error_t ccmEncrypt(const CipherAlgo *cipher, void *context, const uint8_t *n,
   size_t nLen, const uint8_t *a, size_t aLen, const uint8_t *p, uint8_t *c,
   size_t length, uint8_t *t, size_t tLen)
{
   error_t error;
   uint8_t b0[16];
   uint8_t authTag[16];
 
   //The CRYP module only supports AES cipher algorithm
   if(cipher != AES_CIPHER_ALGO)
      return ERROR_INVALID_PARAMETER;
 
   //Make sure the cipher context is valid
   if(context == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Format first block B(0)
   error = ccmFormatBlock0(length, n, nLen, aLen, tLen, b0);
   //Invalid parameters?
   if(error)
      return error;
 
   //Perform AES-CCM encryption
   ccmProcessData(context, b0, a, aLen, p, c, length, authTag,
      AES_CR_MODE_ENCRYPTION);
 
   //Copy the resulting authentication tag
   osMemcpy(t, authTag, tLen);
 
   //Successful processing
   return NO_ERROR;
}
 
 
/**
 * @brief Authenticated decryption using CCM
 * @param[in] cipher Cipher algorithm
 * @param[in] context Cipher algorithm context
 * @param[in] n Nonce
 * @param[in] nLen Length of the nonce
 * @param[in] a Additional authenticated data
 * @param[in] aLen Length of the additional data
 * @param[in] c Ciphertext to be decrypted
 * @param[out] p Plaintext resulting from the decryption
 * @param[in] length Total number of data bytes to be decrypted
 * @param[in] t MAC to be verified
 * @param[in] tLen Length of the MAC
 * @return Error code
 **/
 
error_t ccmDecrypt(const CipherAlgo *cipher, void *context, const uint8_t *n,
   size_t nLen, const uint8_t *a, size_t aLen, const uint8_t *c, uint8_t *p,
   size_t length, const uint8_t *t, size_t tLen)
{
   error_t error;
   size_t i;
   uint8_t mask;
   uint8_t b0[16];
   uint8_t authTag[16];
 
   //The CRYP module only supports AES cipher algorithm
   if(cipher != AES_CIPHER_ALGO)
      return ERROR_INVALID_PARAMETER;
 
   //Make sure the cipher context is valid
   if(context == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Format first block B(0)
   error = ccmFormatBlock0(length, n, nLen, aLen, tLen, b0);
   //Invalid parameters?
   if(error)
      return error;
 
   //Perform AES-CCM decryption
   ccmProcessData(context, b0, a, aLen, c, p, length, authTag,
      AES_CR_MODE_DECRYPTION);
 
   //The calculated tag is bitwise compared to the received tag
   for(mask = 0, i = 0; i < tLen; i++)
   {
      mask |= authTag[i] ^ t[i];
   }
 
   //The message is authenticated if and only if the tags match
   return (mask == 0) ? NO_ERROR : ERROR_FAILURE;
}
 
#endif
#endif