STM32CubeF4

@verbatim
******************** (C) COPYRIGHT 2017 STMicroelectronics *******************
* @file CRYP/CRYP_AESGCM/readme.txt
* @author MCD Application Team
* @brief Description of the CRYP AES Galois/counter mode (GCM)encryption
* decryption mode and TAG generation.
******************************************************************************
* @attention
*
* Copyright (c) 2017 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
@endverbatim

@par Example Description

How to use the CRYPTO peripheral to encrypt/decrypt data(Plaintext/Ciphertext) using
AES Galois/counter mode (GCM)and generate the authentication TAG .

At the beginning of the main program the HAL_Init() function is called to reset
all the peripherals, initialize the Flash interface and the systick.
The SystemClock_Config() function is used to configure the system clock for STM32F479xx Devices.

The AES-GCM mode requires:
1. Plaintext/Ciphertext: which will be authenticated and encrypted/decrypted. Its
size must be a multiple of 4 words. if it's not, which is the case in this
example, it must be padded either manually by user ( put input padded Size
equal to 16 in this example)or automatically by the driver( in this case put
real input Size here 15).
in our example, the size is set to 15, so the padding is done by the driver.

2. HeaderMessage: authenticated header (also knows as Additional Authentication Data AAD)
this part of the message is only authenticated, not encrypted.
HeaderSize is the size of header buffer in word. should be a multiple of 4 words.
if it's not, which is the case in this example, it must be padded exactly like Plaintext.
in our example, the headersize is set to 5, so the padding is done by the driver.

3. InitVector or the Initial Counter Block (ICB)composed of IV and counter.

4. Key: is the parameter which determines the cipher text. In this example the key
size is 128 bits = 4 words but it can be tailored to 192 bits and 256 bits.

CRYP peripheral must be initialized once from the beginning, then for each operation of
encryption/decryption, only configuration should be made if needed.

The AES-GCM encryption and TAG generation provides :
1. Encryptedtext: which is the encryption result of Plaintext, it is compared to Ciphertext.
2. TAG: the Message Authentication Code generated after the encryption and it's compared
to ExpectedTAG.

The AES-GCM decryption and TAG generation provides :
1. Decryptedtext: which is the Decryption result of Ciphertext, it is compared to Plaintext.
2. TAG: the Message Authentication Code generated after the encryption and it's compared
to ExpectedTAG.

STM32469I-EVAL LEDs are used to monitor the encryption/decryption and TAG generation status:
- LED1(GREEN) is ON when encryption/decryption and TAG generation is right.
- LED3(RED) is ON when encryption or decryption or TAG generation is wrong.

@note Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds)
based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from
a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower)
than the peripheral interrupt. Otherwise the caller ISR process will be blocked.
To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.

@note The application needs to ensure that the SysTick time base is always set to 1 millisecond
to have correct HAL operation.

@par Keywords

Security, CRYP, GCM , NIST Special Publication 800-38d, hardware CRYP

@par Directory contents

- CRYP/CRYP_AESGCM/Inc/stm32f4xx_hal_conf.h HAL configuration file
- CRYP/CRYP_AESGCM/Inc/stm32f4xx_it.h Interrupt handlers header file
- CRYP/CRYP_AESGCM/Inc/main.h Header for main.c module
- CRYP/CRYP_AESGCM/Src/stm32f4xx_it.c Interrupt handlers
- CRYP/CRYP_AESGCM/Src/main.c Main program
- CRYP/CRYP_AESGCM/Src/stm32f4xx_hal_msp.c HAL MSP module
- CRYP/CRYP_AESGCM/Src/system_stm32f4xx.c STM32F4xx system source file

@par Hardware and Software environment

- This example runs on STM32F479xx devices.

- This example has been tested with an STMicroelectronics STM32469I-EVAL RevB
board and can be easily tailored to any other supported device
and development board.

@par How to use it ?

In order to make the program work, you must do the following:
- Open your preferred toolchain
- Rebuild all files and load your image into target memory
- Run the example