How to make a password program in C++

Before understanding the password program, one must know about a password and why it is required.

Password: A password is a word that permits access to somewhere or something. A password is for the safety of your private information. Passwords usually contain digits, alphabets, and special characters. A strong password includes alphabets, numerals, at least one capital letter, and special characters.

Alphabets - {a to z, A to Z} 
Digits - {0 to 9}
Special characters such as @, $, #, & etc.

A password should not be your name, mobile number, or a sequence of numbers or characters such as {123456}. These are considered weak passwords, and they can be hacked easily. The below program is for a password generator.

Program

#include <iostream>
#include <cstdlib>   //contains rand(), srand() functions
#include <ctime>
using namespace std; 
static const char alphanumeric[]="0123456789" "!@#$%^&*" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz"; 
int stringLen=sizeof(alphanumeric)-1; 
char RandomGen()
{ 
return alphanumeric[rand()%stringLen]; 
} 
int main() 
{ 
int n,c=0,s=0;
srand(time(0));
cout<<"Enter length of the password:";
cin>>n;
cout<<n<<endl;
cout<<"Password generated is:";
N:
char C;
string D;
for(int z=0; z < n; z++) 
{ 
C=RandomGen();
D+=C;
if(isdigit(C))
{
c++;
}
if(C=='!' || C=='@' || C=='$' || C=='%' ||  C=='^' || C=='&'|| C=='*'|| C=='#')
{
s++;
}
}
if(n>2 && (s==0 || c==0))
{
goto N; 
}
cout<<D; 
return 0; 
}

//A password usually has at least eight characters.

Output 1

Enter length of the password:8
8
Password generated is:3wF3$jD4

In Output 1, the length of the password is eight characters long. Therefore, a random 8-character password has been created. The password generated is “3wF3$jD4”. The generated password contains digits, special characters, and alphabets. Consequently, it is considered a strong password.

Output 2

 Enter length of the password:9
9
Password generated is:RTTC*RrTC

In Output 2, the length of the password is taken as 9. Therefore, a random 9-character password is created. The password generated is “RTTC*RrTC". The generated password contains digits, special characters, and alphabets. Consequently, it is considered a strong password.

Output 3

Enter length of the password:15
15
Password generated is:$6h*pSDxJ4&J7A^

In Output 3, the length of the password is taken as 15. Therefore, a random 15-character password is created. The password generated is “$6h*pSDxJ4&J7A^”. The generated password contains digits, special characters, and alphabets. Therefore, it is considered a strong password. Here, the RandomGen() function returns

Explanation of the program

For generating a password, a randomizing function is used. The cstdlib library in C++ has this randomizing function. Alphanumeric characters include alphabets and numbers.

rand() is the inbuilt function in C++ language, this function is available in <cstdlib>. A randomized sequence is generated by using rand(). Every time the code is executed, a new password is generated. The srand() function is an inbuilt function in C++ is available <cstdlib>. The srand() function

static const char alphanumeric[]="0123456789" "!@#$%^&*" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz";

The alphanumeric[] contains the numbers, special characters, and alphabets (lower and upper). By using this program, one can use the generated password of any specified length.

C++ Program to check if the password is correct or incorrect

#include <iostream>
#include <string>
using namespace std;


int main(){
    string password = "pass1234";
    string input;
    cout << "enter the password: ";
    cin >> input;
    if (input==password){
        cout << "Correct password" << endl;
    }else{
        cout << "Incorrect password" << endl;
    }
    return 0;
}

Output 1

enter the password: pass1234
Correct password

In Output 1, the user enters the string as pass1234. The string entered by the user matches the password. Therefore, the user input is the correct password.

Output 2

enter the password: hello1234
Incorrect password

In Output 2, the user enters the string as hello1234. The string entered by the user does not match the password. Therefore, the user input is the Incorrect password.

Output 3:

enter the password: pass123
Incorrect password

In Output 2, the user enters the string as pass123. The string entered by the user does not match the password. Therefore, the user input is the Incorrect password.

Explanation of the program

In the above program, the string variable password contains the sequence "pass1234". The user enters a string sequence, and the entered sequence compares with the stored sequence ("pass1234"). The password is correct when "pass1234" matches with the sequence entered by the user, and the password is incorrect when "pass1234" does not correspond with the sequence entered by the user.