I have created a password checker in c programming but it is not working can anyone please check it and say what is wrong in this.‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎‎

#include<stdio.h>
#include<stdbool.h>

int main() {
    int otp[4];   //array for storing the true password entered by user at first
    int pto[4];   //array for storing password for login
    int count = 4,i;
    bool pass = true;

    printf("enter a new password:  ");

    for (int i = 0; i < count; i  ) {
        scanf("%d", & otp[i]);  //for storing the true password
    }

    printf("\n\n --- Login page --- ");
    printf("\nenter your password : ");

    for (i = 0; i < count; i  ) {
        scanf(" %d", & pto[i]);   //asking for password for login
    }

    for (i = 0; i < count; i  ) {   //check for password
        if (otp[i] == pto[i]) {
            pass = true;
        } else {
            pass = false;
        }
    }

    while (pass == false) {     //if password is wrong
        printf("\n---- password din't match ----\nenter your password again : ");

        for (i = 0; i < count; i  ) {
            scanf(" %d", & pto[i]);
        }

        for (i = 0; i < count; i  ) {
            if (otp[i] == pto[i]) {
                pass = true;
            } else {
                pass = false;
            }
        }
    }


    printf("\n Your password is correct!");

    return 0;
}

And should I use int or char to store passwords,if i use int also that part works if char also it works but sometimes it wont work,

CodePudding user response：

This loop ultimately only cares if the last value in each array match or not.

for (i = 0; i < count; i  ) {
    if (otp[i] == pto[i]) {
        pass = true;
    } else {
        pass = false;
    }
}

For example, comparing { 1, 2, 3, 4 } and { 4, 4, 4, 4 } would result in pass being true after the loop, despite the obvious differences.

Instead, set the flag to false, and break from your loop as soon as a mismatch occurs.

bool matching = true;

for (size_t i = 0; i < length; i  ) {
    if (array_one[i] != array_two[i]) {
        matching = false;
        break;
    }
}

If a mismatch never occurs, the flag will remain true afterwards.

---

Usually passwords are text that is hashed (with a salt) before being stored. Password verification is done by comparing hashes. For example, take a look at the man 3 crypt library function.

The use of a fixed-length series of plain integers for a 'password' is atypical, but for a toy program it is fine.

---

Here is an example program to study.

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>

#define KEY_LENGTH 4

void get_key(int *key, size_t length) {
    for (size_t i = 0; i < length; i  ) {
        if (1 != scanf("%d", &key[i])) {
            fprintf(stderr, "Could not read integer input.\n");
            exit(EXIT_FAILURE);
        }
    }
}

bool match_key(int *one, int *two, size_t length) {
    for (size_t i = 0; i < length; i  )
        if (one[i] != two[i])
            return false;

    return true;
}

int main(void) {
    int key[KEY_LENGTH];
    int user_key[KEY_LENGTH];

    printf("Set the key (%d integers): ", KEY_LENGTH);
    get_key(key, KEY_LENGTH);

    puts("--- LOGIN ---");

    while (1) {
        printf("Enter the key (%d integers): ", KEY_LENGTH);
        get_key(user_key, KEY_LENGTH);

        if (match_key(key, user_key, KEY_LENGTH))
            break;

        puts("Key mismatch. Retrying...");
    }

    puts("Welcome to the system.");

}

CodePudding user response：

Since you didn’t specify your problem (besides “it’s not working”), I’ll do my best to list all the possible issues.

Reading integers

scanf("%d", & otp[i]);

Will read a single decimal integer into a position in otp. If the password is 1024, the first time through the loop (iteration) will read 1024 into otp[0]. In the second iteration, scanf() will wait until another number is available on standard input. Once it’s available, it will read it into otp[1], and so on. This scanf() loop really reads in 4 different integers, separated by newlines. It would be much easier to do only one scanf() for one integer, like this:

int main() {
    int otp;
    int pto;
    bool pass = true;
    
    printf("enter a new password:  ");
    
    scanf("%d", &otp);

You could also scan a 4-character string by using char arrays:

int main() {
    char otp[5]; //4 digits and 1 NUL-terminator
    char pto[5];
    bool pass = true;
    
    printf("enter a new password:  ");
    
    scanf("%4s", otp);

Password-checking logic error

As @Oka explained, your checker has a logic error. If using an integer, you could simply check

if (opt == pto) {
    //correct
} else {
    //incorrect
}

If using a char array (string), you could use

if (!strcmp(otp, pto)) {
    //correct
} else {
    //incorrect
}

You would have to #include <string.h> for strcmp().

Standard output buffer

The “enter a new password: ” prompt is not printed until the stdout buffer is flushed. This usually only happens when a newline is printed. You have to

fflush(stdout);

right after printing the prompt if you want it to appear.