4.3.2 AES Engine

Use the AES engine to encrypt/decrypt a stream of bytes. Using the HAL APIs, the user can perform Cipher Block Chaining (CBC) or Electronic Codebook (ECB) encryption and decryption with the HAL_AES_EncryptReq() function. The following code is an explanation of the inputs with an example:

void HAL_AES_EncryptReq(HAL_AES_EncryptReq_t *reqParams_s)

The user can perform the following actions in the enum with the above API:

/** Defines HAL AES commands such as setkey, cbc encrypt, cbc decrypt etc */
typedef enum
{
  SM_SET_KEY_COMMAND = 0,
  SM_ECB_ENCRYPT_COMMAND,
  SM_CBC_ENCRYPT_COMMAND,
  SM_ECB_DECRYPT_COMMAND,
  SM_CBC_DECRYPT_COMMAND,
} HAL_AesCmd_t;

1. To set the key in the AES engine before performing encryption/decryption:

   /* Declare a memory for Encrypt request*/
   HAL_AES_EncryptReq_t  appSetKeyReq;
   
   /* define a callback after key is set*/
   void setAesKeyConf(void)
   {
       .. 
   }
   appSetKeyReq.aesCmd = SM_SET_KEY_COMMAND;
   appSetKeyReq.text = &key; // 16 bytes of key
   appSetKeyReq.blockcount = 1; // 128-bit block
   appSetKeyReq.encryptConf = setAesKeyConf;
   
   HAL_AES_EncryptReq(&appSetKeyReq);

2. To perform ECB encryption after setting the key:

   /* Declare a memory for Encrypt request*/
   HAL_AES_EncryptReq_t  appEncryptReq;
   
   /* define a callback after key is set*/
   void aesEncryptConf(void)
   {
     // Action to be taken after the encryption is completed for a block
     ..
     .. 
   }
   appEncryptReq.aesCmd = SM_ECB_ENCRYPT_COMMAND;
   appEncryptReq.text = &text; // 16 bytes of text to encrypt
   appEncryptReq.blockcount = 1; // 128-bit block
   appEncryptReq.encryptConf = aesEncryptConf;
   
   HAL_AES_EncryptReq(&appEncryptReq);