Password strength checker in C++

In this tutorial, we will learn how to create a password strength checker in C++. We need our users to create a strong password so that their data is more secure. A strong password is supposed to contain uppercase English letters, lowercase English letters, special characters, digits, etc. Let’s gather more knowledge about a strong password and see how we can create a program to check if it is so.

Password strength checker in C++

Let’s define a strong password for our users. A password is strong if:

• It contains at least one uppercase letter.
• It contains at least one lowercase letter.
• It contains at least one digit.
• It has at least one character which is neither a letter nor a number.
• Its length must be more than 8 characters.

Let’s say if a password satisfies all the above conditions, it is a strong password. If a password is not strong and satisfies at least three of the first four conditions and its length is greater than or equal to 6 characters, then it is a moderate password. In all other cases, the password is weak.

Let’s understand this with some examples.

Example 1

Password: CodeSpeedy@1213

Since the above password satisfies all the specified conditions, it is a strong password.

Example 2

Password: Code#1

The above password is a moderate password.

Example 3

Password: Name

This is a weak password.

Program: Check password strength in C++

See the example code for a better understanding.

#include <iostream>
using namespace std;

int main()
{
  int l_case=0, u_case=0, digit=0, special=0;
  string str;
  cout<<"Enter input string."<<endl;
  
  cin>>str;
  int l=str.length(),i;
  
  for(i=0;i<l;i++)
  {
    if(islower(str[i]))
      l_case=1;
    if(isupper(str[i]))
      u_case=1;
    if(isdigit(str[i]))
      digit=1;
    if(!isalpha(str[i]) && !isdigit(str[i]))
      special=1;	
  }
  
  if(l_case && u_case && digit && special && l>=8)
    cout<<"Strong password."<<endl;
  else if((l_case+u_case+digit+special>=3) && l>=6)
    cout<<"Moderate password"<<endl;
  else
    cout<<"Weak password"<<endl;
    
  
  return 0;
}

The output of the program will  be:

Enter input string.
CodeSpeedy@1213
Strong password.

Enter input string.
Code#1
Moderate password

Enter input string.
Name
Weak password