main.c

/******************************************************************************
* File Name:   main.c
*
* Description: This is the source code for the HAL: MCU Cryptography: True
* Random Number Generation Example for ModusToolbox.
*
* Related Document: See README.md
*
*
*******************************************************************************
* Copyright 2022, Cypress Semiconductor Corporation (an Infineon company) or
* an affiliate of Cypress Semiconductor Corporation.  All rights reserved.
*
* This software, including source code, documentation and related
* materials ("Software") is owned by Cypress Semiconductor Corporation
* or one of its affiliates ("Cypress") and is protected by and subject to
* worldwide patent protection (United States and foreign),
* United States copyright laws and international treaty provisions.
* Therefore, you may use this Software only as provided in the license
* agreement accompanying the software package from which you
* obtained this Software ("EULA").
* If no EULA applies, Cypress hereby grants you a personal, non-exclusive,
* non-transferable license to copy, modify, and compile the Software
* source code solely for use in connection with Cypress's
* integrated circuit products.  Any reproduction, modification, translation,
* compilation, or representation of this Software except as specified
* above is prohibited without the express written permission of Cypress.
*
* Disclaimer: THIS SOFTWARE IS PROVIDED AS-IS, WITH NO WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, NONINFRINGEMENT, IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress
* reserves the right to make changes to the Software without notice. Cypress
* does not assume any liability arising out of the application or use of the
* Software or any product or circuit described in the Software. Cypress does
* not authorize its products for use in any products where a malfunction or
* failure of the Cypress product may reasonably be expected to result in
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*******************************************************************************/

#include "cyhal.h"
#include "cybsp.h"  
#include "cy_retarget_io.h"
           
/*******************************************************************************
* Macros
********************************************************************************/
/* Macro for the maximum value of the random number generated in bits */
#define ASCII_7BIT_MASK                 (0x7F)

#define PASSWORD_LENGTH                 (8u)
#define ASCII_VISIBLE_CHARACTER_START   (33u)
#define ASCII_RETURN_CARRIAGE           (0x0D)

#define SCREEN_HEADER "\r\n__________________________________________________"\
           "____________________________\r\n*\tHAL: MCU Cryptography: "\
           "True Random Number Generation\r\n*\r\n*\tThis code example "\
           "demonstrates generating a One-Time Password (OTP)\r\n*\tusing the"\
           " True Random Number generation feature of MCU\r\n*\t"\
           "cryptography block\r\n*\r\n*\tUART Terminal Settings\tBaud Rate:"\
           "115200 bps 8N1 \r\n*"\
           "\r\n__________________________________________________"\
           "____________________________\r\n\n"

#define SCREEN_HEADER1 "\r\n================================================="\
           "=============================\r\n"

/* \x1b[2J\x1b[;H - ANSI ESC sequence for clear screen */
#define CLEAR_SCREEN         "\x1b[2J\x1b[;H"

/*******************************************************************************
* Function Prototypes
********************************************************************************/
void generate_password();
uint8_t check_range(uint8_t value);

/*******************************************************************************
* Global Variables
********************************************************************************/

/* Uart object used for reading character from terminal */
extern cyhal_uart_t cy_retarget_io_uart_obj;

/* Variable for storing character read from terminal */
uint8_t uart_read_value;

/*******************************************************************************
* Function Name: main 
********************************************************************************
* Summary:
* This is the main function for CM4 CPU. It configures the Crypto block to 
* generate random number and convert it to a alpha-numeric password. A new 
* password is generated every time  the user presses the Enter key.
*
* Parameters:
*  void
*
* Return:
*  int
*
*******************************************************************************/
int main(void)
{
    cy_rslt_t result;

    /* Initialize the device and board peripherals */
    result = cybsp_init();
    
    /* Board init failed. Stop program execution */
    if (result != CY_RSLT_SUCCESS)
    {
        CY_ASSERT(0);
    }

    /* Enable global interrupts */
    __enable_irq();
    
    /* Initialize retarget-io to use the debug UART port */
    result = cy_retarget_io_init(CYBSP_DEBUG_UART_TX, CYBSP_DEBUG_UART_RX, \
                                 CY_RETARGET_IO_BAUDRATE);
    
    /* retarget-io init failed. Stop program execution */
    if (result != CY_RSLT_SUCCESS)
    {
        CY_ASSERT(0);
    }

    /* \x1b[2J\x1b[;H - ANSI ESC sequence for clear screen */
    printf(CLEAR_SCREEN);

    printf(SCREEN_HEADER);

    printf("Press the Enter key to generate password\r\n");

    for(;;)
    {
        /* Check if 'Enter' key was pressed */
        if (cyhal_uart_getc(&cy_retarget_io_uart_obj, &uart_read_value, 1) == CY_RSLT_SUCCESS)
        {
            if (uart_read_value == ASCII_RETURN_CARRIAGE)
            {
                /* Generate a password of 8 characters in length */
                generate_password();
            }
        }
    }
}

/*******************************************************************************
* Function Name: generate_password
********************************************************************************
* Summary: This function generates a 8 character long password
*
* Parameters:
*  None
*
* Return
*  void
*
*******************************************************************************/
void generate_password()
{
    int8_t index;
    uint32_t random_val;
    uint8_t temp_value = 0;

    /* Array to hold the generated password. Array size is inclusive of
       string NULL terminating character */
    uint8_t password[PASSWORD_LENGTH + 1]= {0};
    cy_rslt_t result;

    cyhal_trng_t trng_obj;

    /* Initialize the TRNG generator block*/
    result = cyhal_trng_init(&trng_obj);

    if (result == CY_RSLT_SUCCESS)
    {

        for (index = 0; index < PASSWORD_LENGTH;)
        {
            /* Generate a random 32 bit number*/
            random_val = cyhal_trng_generate(&trng_obj);

            uint8_t bit_position  = 0;

            for(int8_t j=0;j<4;j++)
            {
                /* extract byte from the bit position offset 0, 8, 16, and 24. */
                temp_value=((random_val>>bit_position )& ASCII_7BIT_MASK);
                temp_value=check_range(temp_value);
                password[index++] = temp_value;
                bit_position  = bit_position  + 8;
            }
         }

        /* Terminate the password with end of string character */
        password[index] = '\0';

        /* Display the generated password on the UART Terminal */
        printf("One-Time Password: %s\r\n\n",password);
        printf("Press the Enter key to generate new password\r\n");
        printf(SCREEN_HEADER1);

        /* Free the TRNG generator block */
        cyhal_trng_free(&trng_obj);
    }
}

/*******************************************************************************
* Function Name: check_range
********************************************************************************
* Summary: This function check if the generated random number is in the 
*          range of alpha-numeric, special characters ASCII codes.  
*          If not, convert to that range
*
* Parameters:
*  uint8_t
*
* Return
*  uint8_t 
*
*******************************************************************************/
uint8_t check_range(uint8_t value)
{
    if (value < ASCII_VISIBLE_CHARACTER_START)
    {
         value += ASCII_VISIBLE_CHARACTER_START;
    }
     return value;
}

/* [] END OF FILE */