Question
HAL_CRYPEx_AES() maximum number of output bytes?
I am using an STM32L4S9ZIJX part and attempting to encrypt a 256KB buffer (actually 262,144 - 16 = 262,128 bytes) using AES256 CTR mode in polling mode.
I created a wrapper function to perform the encryption:
int encrypt_CTR_mode(uint8_t* key, uint8_t* IV, uint8_t* plaintext, uint32_t pt_length,
uint8_t* ciphertext)
{
// Deinit old parameters
if (HAL_CRYP_DeInit(&hcryp) != HAL_OK)
{
LOG(error, "ERROR: HAL_CRYP_DeInit() failed\n");
return -1;
}
// Setup new params
hcryp.Init.DataType = CRYP_DATATYPE_32B;
hcryp.Init.KeySize = CRYP_KEYSIZE_256B;
hcryp.Init.OperatingMode = CRYP_ALGOMODE_ENCRYPT;
hcryp.Init.ChainingMode = CRYP_CHAINMODE_AES_CTR;
hcryp.Init.KeyWriteFlag = CRYP_KEY_WRITE_ENABLE;
hcryp.Init.pKey = key;
hcryp.Init.pInitVect = IV;
// Init new parameters
if (HAL_CRYP_Init(&hcryp) != HAL_OK)
{
LOG(error, "ERROR: HAL_CRYP_Init() failed\n");
return -1;
}
// Encrypt plaintext
HAL_StatusTypeDef rc;
rc = HAL_CRYPEx_AES(&hcryp, plaintext, pt_length, ciphertext, 5000);
if (rc != HAL_OK)
{
LOG(error, "ERROR: HAL_CRYPEx_AES() -- %d\n", rc);
return -1;
}
return 0;
}
The function returns successfully but I only get 65,520 (0xFFF0) output bytes even though I'm passing in 262,128 to HAL_CRYPEx_AES(). Is there some limitation for the maximum output length of HAL_CRYPEx_AES()? I can't find any such limitation documented.